Journal of Composites Science

Research

11 pages, 2645 KiB

Open AccessArticle

Characterization of Recycled/Virgin Polyethylene Terephthalate Composite Reinforced with Glass Fiber for Automotive Applications

by Valentina Volpe, Maria Sofia Lanzillo, Alfonso Molaro, Giovanni Affinita and Roberto Pantani

J. Compos. Sci. 2022, 6(2), 59; https://doi.org/10.3390/jcs6020059 - 17 Feb 2022

Cited by 11 | Viewed by 3290

Abstract

The use of recycled polyethylene terephthalate (PET) as a matrix for composite materials based on glass fiber reinforced virgin PET could be a cost-effective and environmentally friendly way to upgrade the bottle-grade recycled PET into engineering-grade PET for injection molding. In this work, [...] Read more.

The use of recycled polyethylene terephthalate (PET) as a matrix for composite materials based on glass fiber reinforced virgin PET could be a cost-effective and environmentally friendly way to upgrade the bottle-grade recycled PET into engineering-grade PET for injection molding. In this work, a commercial virgin PET reinforced with 50%wt of glass fibers was compounded by mechanical mixing with a recycled PET, in order to minimize breakage of the glass fibers. The obtained compound, composed by 60%wt of recycled pet and 40%wt glass fiber reinforced virgin PET, was injection molded at three different mold temperatures (4, 40 and 80 °C) to analyze the effect of crystallization of the material during the production process. The results in terms of thermal and mechanical properties were compared with those obtained from recycled PET molded in the same conditions. The flexural tests and the analysis of thermal resistance showed that by adding 40%wt of glass fiber reinforced virgin PET to the recycled PET causes a noticeable improvement of crystallization kinetics and of mechanical properties with respect to that of the pure recycled PET, making it suitable for technical applications. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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14 pages, 4122 KiB

Open AccessArticle

The Variance of the Polypropylene α Relaxation Temperature in iPP/a-PP-pPBMA/Mica Composites

by Jesús-María García-Martínez and Emilia P. Collar

J. Compos. Sci. 2022, 6(2), 57; https://doi.org/10.3390/jcs6020057 - 14 Feb 2022

Cited by 3 | Viewed by 2307

Abstract

By considering that the α relaxation related to the glass to rubber transition (obtained by dynamic mechanical analysis) of isotactic polypropylene (iPP) can be identified with the thermal history of the material (and so, with the processing step), this work deals with the [...] Read more.

By considering that the α relaxation related to the glass to rubber transition (obtained by dynamic mechanical analysis) of isotactic polypropylene (iPP) can be identified with the thermal history of the material (and so, with the processing step), this work deals with the changes in this transition temperature (Tα) in polypropylene/mica composites caused by the mutual effect of the other components (mica and interfacial additive). Here, the additive used is a p-phenylen-bis-maleamic grafted atactic polypropylene (aPP-pPBMA) obtained from polymerization wastes (aPP) by the authors. This additive contains 5.0·10⁻⁴ g.mol⁻¹ (15% w/w) grafted pPBMA. In essence, this article has two different objectives: (1) To observe and discuss the changes in Tα of the polymer matrix (iPP) caused by the combined effect of the other components (mica and aPP-pPBMA); and (2) predicting the values for Tα in terms of both aPP-pPBMA and mica content for whatever composition in the experimental space scanned. This task was undertaken by employing a Box–Wilson experimental design assuming the complex character of the interactions between the components of the iPP/aPP-pPBMA/mica system, which define the ultimate properties of the composite. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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11 pages, 3826 KiB

Open AccessArticle

Facile Fabrication of Magnetic Poly(Vinyl Alcohol)/Activated Carbon Composite Gel for Adsorptive Removal of Dyes

by Tao Wen, Baotao Huang and Li Zhou

J. Compos. Sci. 2022, 6(2), 55; https://doi.org/10.3390/jcs6020055 - 11 Feb 2022

Cited by 7 | Viewed by 2291

Abstract

Activated carbon (AC) has been widely utilized for the adsorption of pollutants from water. However, it is difficult to recycle the AC after adsorption. In this paper, we report a facile one-pot approach to fabricate magnetic poly(vinyl alcohol)/AC composite gel (mPVA/AC CG) by [...] Read more.

Activated carbon (AC) has been widely utilized for the adsorption of pollutants from water. However, it is difficult to recycle the AC after adsorption. In this paper, we report a facile one-pot approach to fabricate magnetic poly(vinyl alcohol)/AC composite gel (mPVA/AC CG) by dropwise addition of an aqueous mixture of PVA, AC and iron ions into the ammonia solution. The obtained mPVA/AC CG after freeze-drying shows porous microstructure and favorable magnetic properties. The utilization of mPVA/AC CG for adsorptive removal of methylene blue (MB) and methyl orange (MO) dyes from water was investigated. The mPVA/AC CG not only exhibited good adsorption performance for both MB and MO dyes but also could be readily recycled using a magnet after adsorption. The adsorption process was well described by the pseudo-second-order kinetic model and the Langmuir isotherm model. Considering the simple fabrication process, good adsorption performance and favorable magnetic separation capability, this work provides a viable strategy for combining the features of AC and magnetic gel for fabrication of applicable magnetic adsorbent. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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9 pages, 2818 KiB

Open AccessArticle

Unsaturated Polyester-Based Polymer Concrete Containing Recycled Cathode Ray Tube Glass Aggregate

by Beatrice Malchiodi, Cristina Siligardi and Paolo Pozzi

J. Compos. Sci. 2022, 6(2), 47; https://doi.org/10.3390/jcs6020047 - 1 Feb 2022

Cited by 9 | Viewed by 3026

Abstract

Polymer concrete (PC) is a composite construction material that boasts several advantages, such as lightness, low water permeability, high resistance to corrosive environments, and chemical degradation. Consequently, it has recently attracted interest as an alternative material to the traditional ones for several civil [...] Read more.

Polymer concrete (PC) is a composite construction material that boasts several advantages, such as lightness, low water permeability, high resistance to corrosive environments, and chemical degradation. Consequently, it has recently attracted interest as an alternative material to the traditional ones for several civil applications. In this study, unsaturated polyester resin was considered the matrix phase of PC. Aimed to produce green PC, the commonly dispersed phase of natural aggregate was totally replaced by recycled glass aggregate (RGA) deriving from cathode ray tube (CRT) glass waste. Fine and coarse fractions of non-hazardous CRT glass were considered in different ratios. Chemical and physical analyses were carried out through XRF, particle size distribution and microstructural analysis to characterize RGA. The influence of RGA particle size and percentage on PC performance was investigated by microstructural analysis and aggregate packing, chemical resistance, water absorption, and mechanical analyses, such as bending, impact, and scratch test. Using solely the coarse fraction of RGA led to the manufacturing of a green PC with similar performance to the traditional PC and in addition lower in density. The PC quality mainly depended on the matrix crosslinking which, for PC containing fine RGA, was promoted by adding 4 wt% of silane coupling agent. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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13 pages, 3394 KiB

Open AccessArticle

Effect of Curing Temperature of Epoxy Matrix on the Electrical Response of Carbon Nanotube Yarn Monofilament Composites

by Omar Rodriguez-Uicab, Tannaz Tayyarian and Jandro L. Abot

J. Compos. Sci. 2022, 6(2), 43; https://doi.org/10.3390/jcs6020043 - 26 Jan 2022

Cited by 2 | Viewed by 2345

Abstract

In order to evaluate the capability of carbon nanotube yarn (CNTY)-based composites for self-sensing of temperature, the temperature-dependent electrical resistance of CNTY monofilament composites was investigated using two epoxy resins: one that cures at 130

°

C (CNTY/ERHT) and one that cures at [...] Read more.

In order to evaluate the capability of carbon nanotube yarn (CNTY)-based composites for self-sensing of temperature, the temperature-dependent electrical resistance of CNTY monofilament composites was investigated using two epoxy resins: one that cures at 130

°

C (CNTY/ERHT) and one that cures at room temperature (CNTY/ERRT). The effect of the curing kinetics of these epoxy resins on the electrical response of the embedded CNTY was investigated in prior studies. It was observed that the viscosity and curing kinetics affect the level of wetting and resin infiltration, which govern the electrical response of the embedded CNTY. In this work, the cyclic thermoresistive characterization of CNTY monofilament composites was conducted under heating–cooling, incremental heating–cooling, and incremental dwell cycles in order to study the effect of the curing temperature of the epoxy matrix on the electrical response of the CNTY monofilament composites. Both monofilament composites showed nearly linear and negative temperature coefficients of resistance (TCR) of −7.07 × 10⁻⁴ °C⁻¹ for specimens cured at a high temperature and −5.93 × 10⁻⁴ °C⁻¹ for specimens cured at room temperature. The hysteresis loops upon heating–cooling cycles were slightly smaller for high-temperature cured specimens in comparison to those cured at room temperature. A combination of factors, such as resin infiltration, curing mechanisms, intrinsic thermoresistivity of CNTY, variations in tunneling and contact resistance between the nanotubes and CNT bundles, and the polymer structure, are paramount factors in the thermoresistive sensitivity of the CNTY monofilament composites. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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11 pages, 5491 KiB

Open AccessArticle

A Versatile Strategy for the Fabrication of Poly(ethyl methacrylate) Composites

by Kayla Baker and Igor Zhitomirsky

J. Compos. Sci. 2022, 6(2), 40; https://doi.org/10.3390/jcs6020040 - 24 Jan 2022

Cited by 2 | Viewed by 2418

Abstract

Poly(ethyl methacrylate) (PEMA) is dissolved in ethanol, known to be a non-solvent for PEMA, due to the solubilizing ability of an added bile acid biosurfactant, lithocholic acid (LA). The ability to avoid traditional toxic and carcinogenic solvents is important for the fabrication of [...] Read more.

Poly(ethyl methacrylate) (PEMA) is dissolved in ethanol, known to be a non-solvent for PEMA, due to the solubilizing ability of an added bile acid biosurfactant, lithocholic acid (LA). The ability to avoid traditional toxic and carcinogenic solvents is important for the fabrication of composites for biomedical applications. The formation of concentrated solutions of high molecular weight PEMA is a key factor for the film deposition using the dip coating method. PEMA films provide corrosion protection for stainless steel. Composite films are prepared, containing bioceramics, such as hydroxyapatite and silica, for biomedical applications. LA facilitates dispersion of hydroxyapatite and silica in suspensions for film deposition. Ibuprofen and tetracycline are used as model drugs for the fabrication of composite films. PEMA-nanocellulose films are successfully prepared using the dip coating method. The microstructure and composition of the films are investigated. The conceptually new approach developed in this investigation represents a versatile strategy for the fabrication of composites for biomedical and other applications, using natural biosurfactants as solubilizing and dispersing agents. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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15 pages, 6962 KiB

Open AccessArticle

The Role of Fibre Length on the Fatigue Failure of Injection-Moulded Composites at Elevated Temperatures under a Range of Axial Loading Conditions

by Trevor Sabiston, Bin Li, Waqas Muhammad, Jidong Kang and Carlos Engler-Pinto

J. Compos. Sci. 2022, 6(2), 38; https://doi.org/10.3390/jcs6020038 - 20 Jan 2022

Cited by 6 | Viewed by 2493

Abstract

The effect of fibre length distribution on the fatigue behaviour of an injection-moulded PA66 carbon fibre composite is investigated. Two materials, short carbon fibre with a mean length of 100 microns, and long carbon fibre with a mean length of 580 microns, are [...] Read more.

The effect of fibre length distribution on the fatigue behaviour of an injection-moulded PA66 carbon fibre composite is investigated. Two materials, short carbon fibre with a mean length of 100 microns, and long carbon fibre with a mean length of 580 microns, are subjected to fully reversed fatigue loading at room temperature and three stress ratios at 120 °C. The fatigue results are compared, and fracture surfaces are analyzed to determine the differing failure modes between the materials and loading conditions. At 120 °C, the fibre length has a significant effect on the fatigue behaviour with order of magnitudes of different fatigue life for a given stress amplitude during tensile fatigue loading. Under tensile loading, fatigue failure initates as fibre matrix debonding with pits present due to end effects in the short carbon fibre material. Under compression–compression loading, the fatigue life is matrix-dominated and should be treated as a maximum stress failure. Under this loading, a smooth crack propagates across the sample with buckling as the final failure mode. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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11 pages, 4486 KiB

Open AccessArticle

Role of Solvent Polarity on Dispersion Quality and Stability of Functionalized Carbon Nanotubes

by Dhivakar Rajendran, Rajarajan Ramalingame, Anurag Adiraju, Hanen Nouri and Olfa Kanoun

J. Compos. Sci. 2022, 6(1), 26; https://doi.org/10.3390/jcs6010026 - 11 Jan 2022

Cited by 17 | Viewed by 4751

Abstract

Dispersion of carbon nanotubes (CNT) in solvents and/or polymers is essential to reach the full potential of the CNTs in nanocomposite materials. Dispersion of CNTs is especially challenging due to the van-der-Waals attraction forces between the CNTs, which let them tend to re-bundle [...] Read more.

Dispersion of carbon nanotubes (CNT) in solvents and/or polymers is essential to reach the full potential of the CNTs in nanocomposite materials. Dispersion of CNTs is especially challenging due to the van-der-Waals attraction forces between the CNTs, which let them tend to re-bundle and/or re-aggregate. This paper presents a brief analysis of the quality and stability of functionalized multiwalled carbon nanotubes (fMWCNT) dispersion on polar solvents. A comparative study of functionalized CNT dispersion in water, methyl, and alcohol-based organic solvents has been carried out and the dispersion has been characterized by UV-VIS spectroscopy, electrochemical characterization such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Visual analysis of the dispersion has been investigated for up to 14 days to assess the dispersion’s stability. Based on the material characterization, it was observed that the degree of affinity fMWCNT with -COOH group highly depends on the polarity of the solvent, where the higher the polarity, the better the interaction of fMWCNT with solvents. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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21 pages, 5215 KiB

Open AccessArticle

Thermoelectric Performance of Polypropylene/Carbon Nanotube/Ionic Liquid Composites and Its Dependence on Electron Beam Irradiation

by Oliver Voigt, Beate Krause, Petra Pötschke, Michael T. Müller and Sven Wießner

J. Compos. Sci. 2022, 6(1), 25; https://doi.org/10.3390/jcs6010025 - 11 Jan 2022

Cited by 11 | Viewed by 2909

Abstract

The thermoelectric behavior of polypropylene (PP) based nanocomposites containing single walled carbon nanotubes (SWCNTs) and five kinds of ionic liquids (Ils) dependent on composite composition and electron beam irradiation (EB) was studied. Therefore, several samples were melt-mixed in a micro compounder, while five [...] Read more.

The thermoelectric behavior of polypropylene (PP) based nanocomposites containing single walled carbon nanotubes (SWCNTs) and five kinds of ionic liquids (Ils) dependent on composite composition and electron beam irradiation (EB) was studied. Therefore, several samples were melt-mixed in a micro compounder, while five Ils with sufficiently different anions and/or cations were incorporated into the PP/SWCNT composites followed by an EB treatment for selected composites. Extensive investigations were carried out considering the electrical, thermal, mechanical, rheological, morphological and, most significantly, thermoelectric properties. It was found that it is possible to prepare n-type melt-mixed polymer composites from p-type commercial SWCNTs with relatively high Seebeck coefficients when adding four of the selected Ils. The highest Seebeck coefficients achieved in this study were +49.3 µV/K (PP/2 wt.% SWCNT) for p-type composites and −27.6 µV/K (PP/2 wt.% SWCNT/4 wt.% IL type AMIM Cl) for n-type composites. Generally, the type of IL is decisive whether p- or n-type thermoelectric behavior is achieved. After IL addition higher volume conductivity could be reached. Electron beam treatment of PP/SWCNT leads to increased values of the Seebeck coefficient, whereas the EB treated sample with IL (AMIM Cl) shows a less negative Seebeck coefficient value. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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13 pages, 5671 KiB

Open AccessArticle

Thermal Behavior of a Light Timber-Frame Wall vs. a Theoretical Simulation with Various Insulation Materials

by Konstantinos Ninikas, Porfyrios Tallaros, Andromachi Mitani, Dimitrios Koutsianitis, Georgios Ntalos, Hamid R. Taghiyari and Antonios N. Papadopoulos

J. Compos. Sci. 2022, 6(1), 22; https://doi.org/10.3390/jcs6010022 - 8 Jan 2022

Cited by 5 | Viewed by 2284

Abstract

The objective of this paper is to compare the thermal behavior of a light frame timber wall by measuring 15 test samples with various insulation materials versus a theoretical simulation with the use of a software. This work establishes the variance between the [...] Read more.

The objective of this paper is to compare the thermal behavior of a light frame timber wall by measuring 15 test samples with various insulation materials versus a theoretical simulation with the use of a software. This work establishes the variance between the two different methods to measure the thermal transmittance coefficient of timber walls. It is verified that the mean percentage alteration between the two methods is 4.25%. Furthermore, this approach proved that with the use of a simulation software, additional readings (humidity, vapor flux, heat flux, and vapor pressure) can also be considered and measured, enhancing the overall development of a timber wall. This can provide additional information regarding to the characteristics of the masonry’s elements assisting in an improved design of a timber wall with upgraded performance. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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8 pages, 8559 KiB

Open AccessArticle

A SiO₂/pHEMA-Based Polymer-Infiltrated Ceramic Network Composite for Dental Restorative Materials

by Hiroshi Ikeda, Yohei Kawajiri, Minako Kibune Sodeyama, Haruka Takesue Yano, Yuki Nagamatsu, Chihiro Masaki, Ryuji Hosokawa and Hiroshi Shimizu

J. Compos. Sci. 2022, 6(1), 17; https://doi.org/10.3390/jcs6010017 - 5 Jan 2022

Cited by 3 | Viewed by 1849

Abstract

SiO₂-poly(2-hydroxyethyl methacrylate) (pHEMA)-based composites have been widely used as biomaterials owing to their biocompatibility. However, they have not yet been applied as tooth restorative materials because of their poor mechanical properties. In the present paper, we develop a novel SiO₂ [...] Read more.

SiO₂-poly(2-hydroxyethyl methacrylate) (pHEMA)-based composites have been widely used as biomaterials owing to their biocompatibility. However, they have not yet been applied as tooth restorative materials because of their poor mechanical properties. In the present paper, we develop a novel SiO₂/pHEMA-based composite with a polymer-infiltrated network (PICN) structure for use in dental restorative materials. A mixture of SiO₂ nanoparticles and a poly(vinyl alcohol) binder was sintered at 950 °C to fabricate a porous SiO₂ block. A monomer mixture containing 70 wt%-HEMA/30 wt%-ethylene glycol dimethacrylate and a benzoyl peroxide initiator was infiltrated into the porous SiO₂ block and heat-polymerized to fabricate the SiO₂/pHEMA-based composite with a PICN structure. The composite was characterized according to its mechanical properties, surface free energy, and bonding properties with a dental adhesive. The flexural strength was 112.5 ± 18.7 MPa, the flexural modulus was 13.6 ± 3.4 GPa, and the Vickers hardness was 168.2 ± 16.1, which are similar values to human teeth. The surface free energy of the polar component of the composite was 19.6 ± 2.5 mN/m, suggesting that this composite has an active surface for bonding with the adhesive. The composite bonded well to the adhesive, in the presence of a silane coupling agent. The SiO₂/pHEMA-based composite was demonstrated to be a potential candidate for dental restorative materials. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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14 pages, 7158 KiB

Open AccessArticle

Investigation of Fatigue Behavior of Three Dimensional Interlock Composites by Time-Lapse Micro-Computed Tomography

by Christophe Cruanes, Keerthi Krishna Parvathaneni, Dmytro Vasiukov and Chung Hae Park

J. Compos. Sci. 2022, 6(1), 14; https://doi.org/10.3390/jcs6010014 - 31 Dec 2021

Viewed by 1539

Abstract

The mechanism of the crack propagation in three dimensional (3D) glass-fiber warp interlock epoxy composites under fatigue loading was investigated via time-lapse micro-computed tomography (µCT) observations. Two different composite samples were manufactured by means of a resin transfer molding (RTM) process under two [...] Read more.

The mechanism of the crack propagation in three dimensional (3D) glass-fiber warp interlock epoxy composites under fatigue loading was investigated via time-lapse micro-computed tomography (µCT) observations. Two different composite samples were manufactured by means of a resin transfer molding (RTM) process under two different constant injection pressure conditions to generate intrayarn and interyarn voids separately. Fatigue loads were applied by blocks of 10⁵ cycles and followed by µCT measurements. Regions of interest for micro tomography scans were selected based on hot spots detected by infrared thermography. After the analysis of the obtained data, it was observed that detectable cracks were generally initiated by debonding in the zone between two adjacent warp yarns and grew along their interface. Then, these cracks propagated along one of the warp yarns aligned in the loading direction while remaining in the middle of the specimen cross-section. The coalescence of the cracks and further propagation to the weakest zones were observed around and after the middle lifetime. Finally, we demonstrated the influence of the void defects at different material scales. I was found that interyarn voids have relatively little influence on the fatigue performance whereas they can, sometimes, attract and deviate cracks in the matrix zone between adjacent yarns. It was also shown that the intrayarn voids are crucial to degenerate the fatigue performance of the yarns at the micro-scale. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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14 pages, 6890 KiB

Open AccessArticle

Novel Reactive Flex Configuration in Kiwi Wing Foil Surfboard

by Adrien M. Fat Cheung and Klaudio Bari

J. Compos. Sci. 2022, 6(1), 6; https://doi.org/10.3390/jcs6010006 - 26 Dec 2021

Viewed by 2863

Abstract

The creation of an ideal surfboard is art. The design and construction depend on the individual surfer’s skill level and type of the required performance. In this research, four fuselage concepts were carefully explored to meet the following unique needs: lightweight, strong, and [...] Read more.

The creation of an ideal surfboard is art. The design and construction depend on the individual surfer’s skill level and type of the required performance. In this research, four fuselage concepts were carefully explored to meet the following unique needs: lightweight, strong, and a fast-manufacturing process. The fuselages were manufactured by compression moulding using skin and core materials. The skin material was selected to be unidirectional (UD) carbon fibre, discontinuous carbon fibre (SMC) and Filava quadriaxial fibre impregnated with epoxy, while the core material was selected to be lightweight PVC foam. To assess the mechanical performance, three-point bending has been performed according to BS-ISO 14125 and validated using Finite Element Analysis (FEA) using Ansys software. As expected, the flexural test revealed that the UD carbon fibre fuselage was the strongest and SMC was the weakest, while large deflection was seen in Filava fibre fuselages before failure, showing great reactive flex that promotes projection during surfing. The experimental results show good agreement with FEA simulation, and the locations of the physical failure in the fuselage matches the location of maximum flexural stress obtained from FEA simulation. Although all fuselages were found to carry a surfer weight of 150 kg, including a factor of safety 3, except the SMC fuselage, due to shrinkage. The Filava fibre fuselages were seen to have a large deflection before failure, showing great flexibility to handle high ocean waves. This promotes the potential use of reactive flex in high performance sports equipment, such as surfing boards. A large shrinkage must be taken under consideration during compression moulding that depends on fibre orientation, resin nature, and part geometry. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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15 pages, 4323 KiB

Open AccessArticle

Effectiveness of Sodium Acetate Treatment on the Mechanical Properties and Morphology of Natural Fiber-Reinforced Composites

by Dionisio Badagliacco, Vincenzo Fiore, Carmelo Sanfilippo and Antonino Valenza

J. Compos. Sci. 2022, 6(1), 5; https://doi.org/10.3390/jcs6010005 - 25 Dec 2021

Cited by 8 | Viewed by 3092

Abstract

This paper aims to investigate the ability of an eco-friendly and cheap treatment based on sodium acetate solutions to improve the mechanical properties of flax fiber-reinforced composites. Flax fibers were treated for 5 days (i.e., 120 h) at 25 °C with mildly alkaline [...] Read more.

This paper aims to investigate the ability of an eco-friendly and cheap treatment based on sodium acetate solutions to improve the mechanical properties of flax fiber-reinforced composites. Flax fibers were treated for 5 days (i.e., 120 h) at 25 °C with mildly alkaline solutions at 5%, 10% and 20% weight content of the sodium salt. Quasi-static tensile and flexural tests, Charpy impact tests and dynamical mechanical thermal (DMTA) tests were carried out to evaluate the mechanical properties of the resulting composites. Fourier transform infrared analysis (FTIR) was used to evaluate the chemical modification on the fibers surface due to the proposed treatment, whereas scanning electron microscope (SEM) and helium pycnometry were used to get useful information about the morphology of composites. It was found that the treatment with 5% solution of sodium acetate leads to the best mechanical performance and morphology of flax fiber-reinforced composites. SEM analysis confirmed these findings highlighting that composites reinforced with flax fibers treated in 5% sodium acetate solution show an improved morphology compared to the untreated ones. On the contrary, detrimental effects on the morphology as well as on the mechanical performance of composites were achieved by increasing the salt concentration of the treating solution. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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19 pages, 7700 KiB

Open AccessArticle

Buckling Optimization of Variable Stiffness Composite Panels for Curvilinear Fibers and Grid Stiffeners

by Sofía Arranz, Abdolrasoul Sohouli and Afzal Suleman

J. Compos. Sci. 2021, 5(12), 324; https://doi.org/10.3390/jcs5120324 - 15 Dec 2021

Cited by 9 | Viewed by 3607

Abstract

Automated Fiber Placement (AFP) machines can manufacture composite panels with curvilinear fibers. In this article, the critical buckling load of grid-stiffened curvilinear fiber composite panels is maximized using a genetic algorithm. The skin is composed of layers in which the fiber orientation varies [...] Read more.

Automated Fiber Placement (AFP) machines can manufacture composite panels with curvilinear fibers. In this article, the critical buckling load of grid-stiffened curvilinear fiber composite panels is maximized using a genetic algorithm. The skin is composed of layers in which the fiber orientation varies along one spatial direction. The design variables are the fiber orientation of the panel for each layer and the stiffener layout. Manufacturing constraints in terms of maximum curvature allowable by the AFP machine are imposed for both skin and stiffener fibers. The effect of manufacturing-induced gaps in the laminates is also incorporated. The finite element method is used to perform the buckling analyses. The panels are subjected to in-plane compressive and shear loads under several boundary conditions. Optimization results show that the percentage difference in the buckling load between curvilinear and straight fiber panels depends on the load case and boundary conditions. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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12 pages, 3913 KiB

Open AccessArticle

Solid-State Hydrogen Fuel by PSII–Chitin Composite and Application to Biofuel Cell

by Yusuke Takahashi, Akinari Iwahashi, Yasumitsu Matsuo and Hinako Kawakami

J. Compos. Sci. 2021, 5(12), 317; https://doi.org/10.3390/jcs5120317 - 1 Dec 2021

Cited by 6 | Viewed by 3209

Abstract

Biomaterials attract a lot of attention as next-generation materials. Especially in the energy field, fuel cells based on biomaterials can further develop clean next-generation energy and are focused on with great interest. In this study, solid-state hydrogen fuel (PSII–chitin composite) composed of the [...] Read more.

Biomaterials attract a lot of attention as next-generation materials. Especially in the energy field, fuel cells based on biomaterials can further develop clean next-generation energy and are focused on with great interest. In this study, solid-state hydrogen fuel (PSII–chitin composite) composed of the photosystem II (PSII) and hydrated chitin composite was successfully created. Moreover, a biofuel cell consisting of the electrolyte of chitin and the hydrogen fuel using the PSII–chitin composite was fabricated, and its characteristic feature was investigated. We found that proton conductivity in the PSII–chitin composite increases by light irradiation. This result indicates that protons generate in the PSII–chitin composite by light irradiation. It was also found that the biofuel cell using the PSII–chitin composite hydrogen fuel and the chitin electrolyte exhibits the maximum power density of 0.19 mW/cm². In addition, this biofuel cell can drive an LED lamp. These results indicate that the solid-state biofuel cell based on the bioelectrolyte “chitin” and biofuel “the PSII–chitin composite” can be realized. This novel solid-state fuel cell will be helpful to the fabrication of next-generation energy. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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28 pages, 7828 KiB

Open AccessArticle

Strength, Shrinkage and Early Age Characteristics of One-Part Alkali-Activated Binders with High-Calcium Industrial Wastes, Solid Reagents and Fibers

by Dhruv Sood and Khandaker M. A. Hossain

J. Compos. Sci. 2021, 5(12), 315; https://doi.org/10.3390/jcs5120315 - 30 Nov 2021

Cited by 12 | Viewed by 2728

Abstract

Alkali-activated binders (AABs) are developed using a dry mixing method under ambient curing incorporating powder-form reagents/activators and industrial waste-based supplementary cementitious materials (SCMs) as precursors. The effects of binary and ternary combinations/proportions of SCMs, two types of powder-form reagents, fundamental chemical ratios (SiO [...] Read more.

Alkali-activated binders (AABs) are developed using a dry mixing method under ambient curing incorporating powder-form reagents/activators and industrial waste-based supplementary cementitious materials (SCMs) as precursors. The effects of binary and ternary combinations/proportions of SCMs, two types of powder-form reagents, fundamental chemical ratios (SiO₂/Al₂O₃, Na₂O/SiO₂, CaO/SiO₂, and Na₂O/Al₂O₃), and incorporation of polyvinyl alcohol (PVA) fibers on fresh state and hardened characteristics of 16 AABs were investigated to assess their performance for finding suitable mix compositions. The mix composed of ternary SCM combination (25% fly-ash class C, 35% fly-ash class F, and 40% ground granulated blast furnace slag) with multi-component reagent combination (calcium hydroxide and sodium metasilicate = 1:2.5) was found to be the most optimum binder considering all properties with a 56 day compressive strength of 54 MPa. The addition of 2% v/v PVA fibers to binder compositions did not significantly impact the compressive strengths. However, it facilitated mitigating shrinkage/expansion strains through micro-confinement in both binary and ternary binders. This research bolsters the feasibility of producing ambient cured powder-based cement-free binders and fiber-reinforced, strain-hardening composites incorporating binary/ternary combinations of SCMs with desired fresh and hardened properties. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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19 pages, 8653 KiB

Open AccessArticle

Influence of Failure Criteria and Intralaminar Damage Progression Numerical Models on the Prediction of the Mechanical Behavior of Composite Laminates

by Aniello Riccio, Concetta Palumbo, Valerio Acanfora, Andrea Sellitto and Angela Russo

J. Compos. Sci. 2021, 5(12), 310; https://doi.org/10.3390/jcs5120310 - 26 Nov 2021

Cited by 17 | Viewed by 2828

Abstract

This work evaluates the effectiveness of commonly adopted local damage evolution methods and failure criteria in finite element analysis for the simulation of intralaminar damage propagation in composites under static loading conditions. The proposed numerical model is based on a User Defined Material [...] Read more.

This work evaluates the effectiveness of commonly adopted local damage evolution methods and failure criteria in finite element analysis for the simulation of intralaminar damage propagation in composites under static loading conditions. The proposed numerical model is based on a User Defined Material subroutine (USERMAT) implemented in Ansys. This model is used to predict the evolution of damage within each specific lamina of a composite laminate by introducing both sudden and gradual degradation rules. The main purpose of the simulations is to quantitatively assess the influence of the adopted failure criteria in conjunction with degradation laws on the accuracy of the numerical predictions in terms of damage evolution and failure load. The mechanical behavior of an open hole tension specimen and of a notched stiffened composite panel under shear loading conditions have been numerically simulated by Progressive Damage Models (PDM). Different failure criteria have been implemented in the developed Ansys USERMAT, together with sudden and gradual degradation rules based on the Continuum Damage Mechanics (CDM) approach. Numerical results have been validated against experimental data to assess the effects of the different failure criteria and damage evolution law on the global mechanical response and local damage predictions in composite laminates. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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17 pages, 4315 KiB

Open AccessArticle

Investigations on Structural and Optical Properties of Various Modifier Oxides (MO = ZnO, CdO, BaO, and PbO) Containing Bismuth Borate Lithium Glasses

by J. Bhemarajam, P. Syam Prasad, M. Mohan Babu, Mutlu Özcan and M. Prasad

J. Compos. Sci. 2021, 5(12), 308; https://doi.org/10.3390/jcs5120308 - 25 Nov 2021

Cited by 23 | Viewed by 3236

Abstract

Bismuth based quaternary glasses with compositions BiBLM: 50Bi₂O₃–20B₂O₃–15Li₂O–15MO (where MO = ZnO, CdO, BaO, and PbO) were processed by conventional melt quenching. The effectiveness of various modifier oxides on the optical and structural [...] Read more.

Bismuth based quaternary glasses with compositions BiBLM: 50Bi₂O₃–20B₂O₃–15Li₂O–15MO (where MO = ZnO, CdO, BaO, and PbO) were processed by conventional melt quenching. The effectiveness of various modifier oxides on the optical and structural properties of the developed glasses was studied systematically by XRD, DSC, FTIR, Raman, and optical absorption (OA) measurements. The synthesized glass specimens were characterized by XRD and the patterns demonstrated an amorphous nature. The physical characteristics such as molar mass, density, and OPD values were found to increase with an increase in the molar mass of the modifier oxides, while there was a decrement in oxygen molar volume, thus resulting in decrement of complete molar volume of the prepared glasses. From DSC analysis, incorrigible reduction and enhancement of T_g and thermal stability among various modifier oxides in the glass network was noticed. Optical absorption data for glass specimens have confirmed the decrease in both direct and indirect optical band gap values among various modifier oxides incorporation. These investigations support the obtained Urbach energy (UE) and metallization criteria of synthesized glasses. The ionic characteristic for the glass specimens were confirmed by the values of electronic polarizability and electronegativity. The Raman and FT-IR spectra of the glass specimens displayed the existence of BiO₃, BiO₆, ZnO₄, CdO₄, BaO₄, BO₃, PbO₄, and BO₄ structural units within the glass matrix. These structural results can support the applications of as-developed glasses in the area of photonics. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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14 pages, 1667 KiB

Open AccessArticle

Higher-Order Free Vibration Analysis of Porous Functionally Graded Plates

by Slimane Merdaci, Hadj Mostefa Adda, Belghoul Hakima, Rossana Dimitri and Francesco Tornabene

J. Compos. Sci. 2021, 5(11), 305; https://doi.org/10.3390/jcs5110305 - 21 Nov 2021

Cited by 23 | Viewed by 3035

Abstract

The present work analyzes the free vibration response of functionally graded (FG) plates made of Aluminum (Al) and Alumina (Al₂O₃) with different porosity distributions, as usually induced by a manufacturing process. The problem is tackled theoretically based on a [...] Read more.

The present work analyzes the free vibration response of functionally graded (FG) plates made of Aluminum (Al) and Alumina (Al₂O₃) with different porosity distributions, as usually induced by a manufacturing process. The problem is tackled theoretically based on a higher-order shear deformation plate theory, while proposing a Navier-type approximation to solve the governing equations for simply-supported plates with different porosity distributions in the thickness direction. The reliability of the proposed theory is checked successfully by comparing the present results with predictions available from literature based on further first-order or higher-order theories. A large parametric study is performed systematically to evaluate the effect of different mechanical properties, such as the material indexes, porosity volume fractions, porosity distributions, and length-to-thickness ratios, on the free vibration response of FG plates, as useful for the design purposes of most engineered materials and composite applications. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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15 pages, 4717 KiB

Open AccessArticle

Mechanical Properties of Compression Moulded Aggregate-Reinforced Thermoplastic Composite Scrap

by Julien Moothoo, Mahadev Bar and Pierre Ouagne

J. Compos. Sci. 2021, 5(11), 299; https://doi.org/10.3390/jcs5110299 - 14 Nov 2021

Cited by 3 | Viewed by 2172

Abstract

Recycling of thermoplastic composites has drawn a considerable attention in the recent years. However, the main issue with recycled composites is their inferior mechanical properties compared to the virgin ones. In this present study, an alternative route to the traditional mechanical recycling technique [...] Read more.

Recycling of thermoplastic composites has drawn a considerable attention in the recent years. However, the main issue with recycled composites is their inferior mechanical properties compared to the virgin ones. In this present study, an alternative route to the traditional mechanical recycling technique of thermoplastic composites has been investigated with the view to increase mechanical properties of the recycled parts. In this regard, the glass/polypropylene laminate offcuts are cut in different grain sizes and processed in bulk form, using compression moulding. Further, the effect of different grain sizes (i.e., different lengths, widths and thicknesses) and other process-related parameters (such as mould coverage) on the tensile properties of recycled aggregate-reinforced composites have been investigated. The tensile properties of all composite samples are tested according to ISO 527-4 test method and the significance of test results is evaluated according to Student’s t-test and Fisher’s F-test respectively. It is observed that the tensile moduli of the recycled panels are close to the equivalent quasi-isotropic continuous fibre-reinforced reference laminate while there is a noteworthy difference in the strengths of the recycled composites. At this stage, the manufactured recycled composites show potential for stiffness-driven application. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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9 pages, 733 KiB

Open AccessArticle

In Vitro Weight Loss of Dental Composite Resins and Glass-Ionomer Cements Exposed to a Challenge Simulating the Oral Intake of Acidic Drinks and Foods

by Marco Colombo, Simone Gallo, Marco Chiesa, Claudio Poggio, Andrea Scribante, Paolo Zampetti and Giampiero Pietrocola

J. Compos. Sci. 2021, 5(11), 298; https://doi.org/10.3390/jcs5110298 - 13 Nov 2021

Cited by 6 | Viewed by 1847

Abstract

Specific conditions of the oral cavity, such as intake of acidic drinks, foods, and drugs, represent a damage both for teeth as well as restorative materials. The aim of this in vitro study is to assess the influence of an acidic challenge on [...] Read more.

Specific conditions of the oral cavity, such as intake of acidic drinks, foods, and drugs, represent a damage both for teeth as well as restorative materials. The aim of this in vitro study is to assess the influence of an acidic challenge on the weight loss of biomimetic restorative dental materials (composite resins and glass-ionomer cements, respectively). Seven products recently available in the marked have been tested in this study for the two kinds of materials, respectively. Resin composites were divided into Groups 1A–7A, whereas glass-ionomer cements into Groups 1B–7B. A total of six samples was considered for each group, among which two were stored into distilled water (control samples) whereas the other four were immersed into soft drink (Coca-Cola, Coca-Cola Company, Milano, Italy) for 7 days. Respectively, after 1, 3 and 7 days, weight was assessed for each sample and the percentage weight loss was calculated. For all the composite resins (Groups 1A–7A), no significant intergroup or intragroup differences occurred for the weight loss values (p > 0.05). Conversely, all glass-ionomers (Groups 1B–7B) showed a significant and progressive weight loss after 1, 3, and 7 days of acid challenge (p < 0.05) (intragroup differences). This reduction was significantly lower in case of GC Equia Forte + Coat and ChemFil Rock, with respect to the other cements (p < 0.05) (intergroup differences). In conclusions, all the biomimetic composite resins showed a reliable behavior when exposed to acidic erosion, whereas glass-ionomers cements generally tended to solubilize. However, the additional use of a protective layer above these latter materials could reduce this event. Despite these results appear to be interesting from a clinical point of view, future morphological evaluations should be conducted to evaluate the superficial changes of the materials after acidic explosion. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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13 pages, 6236 KiB

Open AccessArticle

Tension-Compression Fatigue Induced Stress Concentrations in Woven Composite Laminate

by Eldho Mathew, Rajaram Attukur Nandagopal, Sunil Chandrakant Joshi, Pinter Armando and Pasi Matteo

J. Compos. Sci. 2021, 5(11), 297; https://doi.org/10.3390/jcs5110297 - 11 Nov 2021

Cited by 3 | Viewed by 1985

Abstract

Tension-compression (T-C) fatigue response is one of the important design criteria for carbon-fibre-reinforced polymer (CFRP) material, as well as stress concentration. Hence, the objective of the current study is to investigate and quantify the stress concentration in CFRP dog-bone specimens due to T-C [...] Read more.

Tension-compression (T-C) fatigue response is one of the important design criteria for carbon-fibre-reinforced polymer (CFRP) material, as well as stress concentration. Hence, the objective of the current study is to investigate and quantify the stress concentration in CFRP dog-bone specimens due to T-C quasi-static and fatigue loadings (with anti-buckling fixtures). Dog-bone specimens with a [(0/90),(45/−45)4]_s layup were fabricated using woven CFRP prepregs and their low-cycle fatigue behaviour was studied at two stress ratios (−0.1 & −0.5) and two frequencies (3 Hz & 5 Hz). During testing, strain gauges were mounted at the centre and edge regions of the dog-bone specimens to obtain accurate, real-time strain measurements. The corresponding stresses were calculated using Young’s moduli. The stress concentration at the specimen edges, due to quasi-static tension, was significant compared to quasi-static compression loads. Furthermore, the stress concentration increased with the quasi-static loading within the elastic limit. Similarly, the stress concentration at the specimen edges, due to tensile fatigue loads, was more significant and consistent than due to compressive fatigue loads. Finally, the effects of the stress ratio and loading frequency on the stress concentration were noted to be negligible. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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15 pages, 3318 KiB

Open AccessArticle

Wrinkle Formation and Initial Defect Sensitivity of Steered Tow in Automated Fiber Placement

by Meisam Kheradpisheh and Mehdi Hojjati

J. Compos. Sci. 2021, 5(11), 295; https://doi.org/10.3390/jcs5110295 - 9 Nov 2021

Cited by 6 | Viewed by 1982

Abstract

This paper aims to study the wrinkle formation of a prepreg with initial defect during steering in automated fiber placement (AFP). Wrinkle formation has a detrimental effect on the mechanical properties of the final product, limiting the AFP applications. A theoretical model for [...] Read more.

This paper aims to study the wrinkle formation of a prepreg with initial defect during steering in automated fiber placement (AFP). Wrinkle formation has a detrimental effect on the mechanical properties of the final product, limiting the AFP applications. A theoretical model for wrinkle formation has been developed in which a Pasternak foundation and a Koiter imperfection model are adapted to model viscoelastic characteristics of the prepreg tack and initial defect of the prepreg, respectively. The initial defect is defined as a slight deviation of the tow’s mid-plane from a horizontal shape. The initial defect is generated in the tow by moving the tow through the guidance system, pressure of the roller, and resin tackiness. Galerkin method, along with the finite difference method (FDM), are employed to solve the wrinkle problem equation. The proposed method is able to satisfy the different boundary conditions for the wrinkle problem completely. The numerical results show that increasing the initial defect leads to a decrease in critical load and an increase in critical steering radius. To validate the theoretical model, experimental results are presented and compared with model-predicted results. It is shown that the model is well able to capture the trends and values of wrinkle formation wavelengths obtained from the experiment. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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15 pages, 2058 KiB

Open AccessArticle

Numerical Application of Effective Thickness Approach to Box Aluminium Sections

by Elide Nastri, Vincenzo Piluso and Alessandro Pisapia

J. Compos. Sci. 2021, 5(11), 291; https://doi.org/10.3390/jcs5110291 - 5 Nov 2021

Cited by 17 | Viewed by 2072

Abstract

The ultimate behaviour of aluminium members subjected to uniform compression or bending is strongly influenced by local buckling effects which occur in the portions of the section during compression. In the current codes, the effective thickness method (ETM) is applied to evaluate the [...] Read more.

The ultimate behaviour of aluminium members subjected to uniform compression or bending is strongly influenced by local buckling effects which occur in the portions of the section during compression. In the current codes, the effective thickness method (ETM) is applied to evaluate the ultimate resistance of slender cross-sections affected by elastic local buckling. In this paper, a recent extension of ETM is presented to consider the local buckling effects in the elastic-plastic range and the interaction between the plate elements constituting the cross-section. The theoretical results obtained with this approach, applied to box-shaped aluminium members during compression or in bending, are compared with the experimental tests provided in the scientific literature. It is observed that the ETM is a valid and accurate tool for predicting the maximum resistance of box-shaped aluminium members during compression or in bending. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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12 pages, 1440 KiB

Open AccessArticle

Low-Frequency Magnetoelectric Effects in Magnetostrictive–Piezoelectric Bilayers: Longitudinal and Bending Deformations

by Dmitry Filippov, Ying Liu, Peng Zhou, Bingfeng Ge, Jiahui Liu, Jitao Zhang, Tianjin Zhang and Gopalan Srinivasan

J. Compos. Sci. 2021, 5(11), 287; https://doi.org/10.3390/jcs5110287 - 28 Oct 2021

Cited by 7 | Viewed by 1824

Abstract

A model for the low-frequency magnetoelectric (ME) effect that takes into consideration the bending deformation in a ferromagnetic and ferroelectric bilayer is presented. Past models, in general, ignored the influence of bending deformation. Based on the solution of the equations of the elastic [...] Read more.

A model for the low-frequency magnetoelectric (ME) effect that takes into consideration the bending deformation in a ferromagnetic and ferroelectric bilayer is presented. Past models, in general, ignored the influence of bending deformation. Based on the solution of the equations of the elastic theory and electrostatics, expressions for the ME voltage coefficients (MEVCs) and ME sensitivity coefficients (MESCs) in terms of the physical parameters of the materials and the geometric characteristic of the structure were obtained. Contributions from both bending and planar deformations were considered. The theory was applied to composites of PZT and Ni with negative magnetostriction, and Permendur, or Metglas, both with positive magnetostriction. Estimates of MEVCs and MESCs indicate that the contribution from bending deformation is significant but smaller than the contribution from planar deformations, leading to a reduction in the net ME coefficients in all the three bilayer systems. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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16 pages, 10486 KiB

Open AccessArticle

Method for the Microstructural Characterisation of Unidirectional Composite Tapes

by Nico Katuin, Daniël M. J. Peeters and Clemens A. Dransfeld

J. Compos. Sci. 2021, 5(10), 275; https://doi.org/10.3390/jcs5100275 - 14 Oct 2021

Cited by 4 | Viewed by 2228

Abstract

The outstanding properties of carbon fibre-reinforced polymer composites are affected by the development of its microstructure during processing. This work presents a novel approach to identify microstructural features both along the tape thickness and through the thickness. Voronoi tessellation-based evaluation of the fibre [...] Read more.

The outstanding properties of carbon fibre-reinforced polymer composites are affected by the development of its microstructure during processing. This work presents a novel approach to identify microstructural features both along the tape thickness and through the thickness. Voronoi tessellation-based evaluation of the fibre volume content on cross-sectional micrographs, with consideration of the matrix boundary, is performed. The method is shown to be robust and is suitable to be automated. It has the potential to discriminate specific microstructural features and to relate them to processing behaviour removing the need for manufacturing trials. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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12 pages, 28561 KiB

Open AccessArticle

Effects of Resin/Filler Adhesion on the Thermal and Electrical Conductivity of Polyimide Nanocomposites

by Yoshimichi Ohki and Naoshi Hirai

J. Compos. Sci. 2021, 5(10), 272; https://doi.org/10.3390/jcs5100272 - 14 Oct 2021

Cited by 4 | Viewed by 2054

Abstract

With an aim to develop a good coil winding insulation film, fillers of boehmite alumina in the shape of a roughly rectangular plate were added with ratios of 10 and 20 wt% to polyimide. The filler surface was untreated or treated with a [...] Read more.

With an aim to develop a good coil winding insulation film, fillers of boehmite alumina in the shape of a roughly rectangular plate were added with ratios of 10 and 20 wt% to polyimide. The filler surface was untreated or treated with a methacrylic or an epoxy silane coupling agent. Such prepared polyimide nanocomposites were subjected to various tests to measure the tensile strength, elastic modulus, complex permittivity, and thermal conductivity. It was found that samples with fillers treated using the methacrylic silane coupling agent have the strongest adhesion at the filler/polyimide interfaces and the lowest dielectric loss factor at high temperatures. A positive relationship between the filler/polyimide adhesion and the thermal conductivity is also indicated. These findings are significant since they indicate that the adhesion status at the filler/polymer interface exerts a strong influence on the thermal and electrical conduction processes in the polymer. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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13 pages, 2385 KiB

Open AccessArticle

Thermal, X-ray Diffraction and Oedometric Analyses of Silt-Waste/NaOH-Activated Metakaolin Geopolymer Composite

by Daniele Moro, Riccardo Fabbri, Jennifer Romano, Gianfranco Ulian, Antonino Calafato, Abbas Solouki, Cesare Sangiorgi and Giovanni Valdrè

J. Compos. Sci. 2021, 5(10), 269; https://doi.org/10.3390/jcs5100269 - 13 Oct 2021

Cited by 7 | Viewed by 2516

Abstract

The present research investigates the possibility to create a silt-waste reinforced composite through a NaOH-activated, metakaolin-based geopolymerization process. In this regard, we used thermal exo–endo analysis, X-ray diffraction (XRD), and oedometric mechanical tests to characterize the produced composites. In our experimental conditions, the [...] Read more.

The present research investigates the possibility to create a silt-waste reinforced composite through a NaOH-activated, metakaolin-based geopolymerization process. In this regard, we used thermal exo–endo analysis, X-ray diffraction (XRD), and oedometric mechanical tests to characterize the produced composites. In our experimental conditions, the tested material mixtures presented exothermic peaks with maximum temperatures of about 100 °C during the studied geopolymerization process. In general, the XRD analyses showed the formation of amorphous components and new mineral phases of hydrated sodalite, natrite, thermonatrite and trona. From oedometric tests, we observed a different behavior of vertical deformation related to pressure (at RT) for the various produced composites. The present work indicated that the proposed geopolymerization process to recycle silt-waste produced composite materials with various and extended mineralogy and chemical–physical properties, largely depending on both the precursors and the specific alkaline-activating solution. Thermal analysis, XRD, and oedometric mechanical tests proved to be fundamental to characterize and understand the behavior of the newly formed composite material. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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16 pages, 7090 KiB

Open AccessArticle

Strain-Mediated Magneto-Electric Effects in Coaxial Nanofibers of Y/W-Type Hexagonal Ferrites and Ferroelectrics

by Ying Liu, Peng Zhou, Bingfeng Ge, Jiahui Liu, Jitao Zhang, Wei Zhang, Tianjing Zhang and Gopalan Srinivasan

J. Compos. Sci. 2021, 5(10), 268; https://doi.org/10.3390/jcs5100268 - 13 Oct 2021

Cited by 5 | Viewed by 1792

Abstract

Nanofibers of Y- or W-type hexagonal ferrites and core–shell fibers of hexagonal ferrites and ferroelectric lead zirconate titanate (PZT) or barium titanate (BTO) were synthesized by electrospinning. The fibers were found to be free of impurity phases, and the core–shell structure was confirmed [...] Read more.

Nanofibers of Y- or W-type hexagonal ferrites and core–shell fibers of hexagonal ferrites and ferroelectric lead zirconate titanate (PZT) or barium titanate (BTO) were synthesized by electrospinning. The fibers were found to be free of impurity phases, and the core–shell structure was confirmed by electron and scanning probe microscopy. The values of magnetization of pure hexagonal ferrite fibers compared well with bulk ferrite values. The coaxial fibers showed good ferroelectric polarization, with a maximum value of 0.85 μC/cm² and 2.44 μC/cm² for fibers with BTO core–Co₂W shell and PZT core–Ni₂Y shell structures, respectively. The magnetization, however, was much smaller than that for bulk hexaferrites. Magneto-electric (ME) coupling strength was characterized by measuring the ME voltage coefficient (MEVC) for magnetic field-assembled films of coaxial fibers. Among the fibers with Y-type, films with Zn₂Y showed a higher MEVC than films with Ni₂Y, and fibers with Co₂W had a higher MEVC than that of those with Zn₂W. The highest MEVC of 20.3 mV/cm Oe was measured for Co₂W–PZT fibers. A very large ME response was measured in all of the films, even in the absence of an external magnetic bias field. The fibers studied here have the potential for use in magnetic sensors and high-frequency device applications. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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9 pages, 3435 KiB

Open AccessArticle

Inverse Proportionality of Thermal Conductivity and Complex Permittivity to Filler-Diameter in Epoxy Resin Composites with Silica

by Yoshimichi Ohki, Naoshi Hirai, Takahiro Umemoto and Hirotaka Muto

J. Compos. Sci. 2021, 5(10), 266; https://doi.org/10.3390/jcs5100266 - 11 Oct 2021

Cited by 6 | Viewed by 1712

Abstract

We prepared six kinds of epoxy resin nanocomposites with silica and an epoxy resin with no silica. The nanocomposites contain silica with different diameters (10, 50, and 100 nm) while their silica contents are 1, 5, 10, and 20 vol%. At 25 and [...] Read more.

We prepared six kinds of epoxy resin nanocomposites with silica and an epoxy resin with no silica. The nanocomposites contain silica with different diameters (10, 50, and 100 nm) while their silica contents are 1, 5, 10, and 20 vol%. At 25 and 100 °C, the thermal conductivity has a nearly proportional dependence on the silica content and exhibits an almost reciprocal proportionality to the diameter of the silica. The latter result indicates that the interaction at filler-resin interfaces plays a significant role in heat transfer. However, this view contradicts an easy-to-understand thought that the filler-resin interfaces should work as a barrier for heat transfer. This in turn indicates that the interaction at filler-resin interfaces controls the bulk properties of the resin when the filler is in a nm size. Although the dielectric constant increases with the addition of the silica filler, its increment from the resin with no silica is the smallest in the resin with the 10-nm silica. Therefore, the addition of the 10-nm silica is adequate for electrical insulation purposes. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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20 pages, 6694 KiB

Open AccessArticle

A Generalized and Modular Framework for Digital Generation of Composite Microstructures

by Ahmet Cecen, Berkay Yucel and Surya R. Kalidindi

J. Compos. Sci. 2021, 5(8), 211; https://doi.org/10.3390/jcs5080211 - 11 Aug 2021

Cited by 9 | Viewed by 2149

Abstract

This paper presents a generalized framework for the digital generation of composite microstructures using filter-based approaches that can devise and utilize a wide variety of cost functions reflecting the desired targets on geometrical and statistical measures. The use of filter-based approaches leads to [...] Read more.

This paper presents a generalized framework for the digital generation of composite microstructures using filter-based approaches that can devise and utilize a wide variety of cost functions reflecting the desired targets on geometrical and statistical measures. The use of filter-based approaches leads to remarkable computational advantages compared to the conventional approaches used currently for microstructure generation. The framework provides a highly modular and flexible approach to generate stochastic ensembles of microstructures meeting user-defined microstructural characteristics. The proposed framework is illustrated in this paper through selected case studies. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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9 pages, 8328 KiB

Open AccessArticle

Computational Investigation of Crack-Induced Hot-Spot Generation in Energetic Composites

by Xingzi Yang, Liqiang Lin, Justin Wilkerson and Xiaowei Zeng

J. Compos. Sci. 2021, 5(8), 210; https://doi.org/10.3390/jcs5080210 - 10 Aug 2021

Cited by 1 | Viewed by 1987

Abstract

The sensitivity of polymer-bonded explosives (PBXs) can be tuned through adjusting binder material and its volume fraction, crystal composition and morphology. To obtain a better understanding of the correlation between grain-level failure and hot-spot generation in this kind of energetic composites as they [...] Read more.

The sensitivity of polymer-bonded explosives (PBXs) can be tuned through adjusting binder material and its volume fraction, crystal composition and morphology. To obtain a better understanding of the correlation between grain-level failure and hot-spot generation in this kind of energetic composites as they undergo mechanical and thermal processes subsequent to impact, a recently developed interfacial cohesive zone model (ICZM) was used to study the dynamic response of polymer-bonded explosives. The ICZM can capture the contributions of deformation and fracture of the binder phase as well as interfacial debonding and subsequent friction on hot-spot generation. In this study, a two-dimensional (2D) finite element (FE) computational model of energetic composite was developed. The proposed computational model has been applied to simulate hot-spot generation in polymer-bonded explosives with different grain volume fraction under dynamic loading. Our simulation showed that the increase of binder phase material volume fraction will decrease the local heat generation, resulting in a lower temperature in the specimen. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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20 pages, 8779 KiB

Open AccessArticle

Chloramphenicol Loaded Sponges Based on PVA/Nanocellulose Nanocomposites for Topical Wound Delivery

by Evangelia D. Balla, Nikolaos D. Bikiaris, Stavroula G. Nanaki, Chrysanthi Papoulia, Konstantinos Chrissafis, Panagiotis A. Klonos, Apostolos Kyritsis, Margaritis Kostoglou, Alexandra Zamboulis and George Z. Papageorgiou

J. Compos. Sci. 2021, 5(8), 208; https://doi.org/10.3390/jcs5080208 - 6 Aug 2021

Cited by 7 | Viewed by 3353

Abstract

In the present study, polymer sponges based on poly(vinyl alcohol) (PVA) were prepared for the topical wound administration of chloramphenicol (CHL), an antibiotic widely used to treat bacterial infections. Nanocellulose fibrils (CNF) were homogenously dispersed in PVA sponges in three different ratios (2.5, [...] Read more.

In the present study, polymer sponges based on poly(vinyl alcohol) (PVA) were prepared for the topical wound administration of chloramphenicol (CHL), an antibiotic widely used to treat bacterial infections. Nanocellulose fibrils (CNF) were homogenously dispersed in PVA sponges in three different ratios (2.5, 5, and 10 wt %) to improve the mechanical properties of neat PVA sponges. Infrared spectroscopy showed hydrogen bond formation between CNF and PVA, while scanning electron microscopy photos verified the successful dispersion of CNF to PVA sponges. The addition of CNF successfully enhanced the mechanical properties of PVA sponges, exhibiting higher compressive strength as the content of CNF increased. The PVA sponge containing 10 wt % CNF, due to its higher compression strength, was further studied as a matrix for CHL delivery in 10, 20, and 30 wt % concentration of the drug. X-ray diffraction showed that CHL was encapsulated in an amorphous state in the 10 and 20 wt % samples, while some crystallinity was observed in the 30 wt % ratio. In vitro dissolution studies showed enhanced CHL solubility after its incorporation in PVA/10 wt % CNF sponges. Release profiles showed a controlled release lasting three days for the sample containing 10 wt % CHL and 1.5 days for the other two samples. According to modelling, the release is driven by a pseudo-Fickian diffusion. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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11 pages, 3859 KiB

Open AccessArticle

Vanadium Dioxide–Iridium Composite Development: Specific Near Infrared Surface Plasmon Resonance

by Adrian Ionut Bercea, Corinne Champeaux, Catalin Daniel Constantinescu and Frédéric Dumas-Bouchiat

J. Compos. Sci. 2021, 5(7), 193; https://doi.org/10.3390/jcs5070193 - 20 Jul 2021

Cited by 3 | Viewed by 2372

Abstract

This work serves as a roadmap for the development of a Vanadium dioxide (VO₂)–Iridium composite based on the self-assembly of closely packed colloidal polystyrene microspheres (P-spheres) coupled with a Pulsed Laser Deposition (PLD) process. The self-assembly of a monolayer of PS [...] Read more.

This work serves as a roadmap for the development of a Vanadium dioxide (VO₂)–Iridium composite based on the self-assembly of closely packed colloidal polystyrene microspheres (P-spheres) coupled with a Pulsed Laser Deposition (PLD) process. The self-assembly of a monolayer of PS is performed on an Al₂O₃-c substrate, using an adapted Langmuir–Blodgett (LB) process. Then, on the substrate covered with P-spheres, a 50-nanometer Iridium layer is deposited by PLD. The Iridium deposition is followed by the removal of PS with acetone, revealing an array of triangular shaped metallic elements formed on the underlaying substrate. In a last deposition step, 50-, 100- and 200-nanometer thin films of VO₂ are deposited by PLD on top of the substrates covered with the Iridium quasi-triangles, forming a composite. Adapting the size of the P-spheres leads to control of both the size of the Iridium micro-triangle and, consequently, the optical transmittance of the composite. Owing to their shape and size the Iridium micro-triangles exhibit localized surface plasmon resonance (LSPR) characterized by a selective absorption of light. Due to the temperature dependent properties of VO₂, the LSPR properties of the composite can be changeable and tunable. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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9 pages, 2037 KiB

Open AccessArticle

Organic Solvent Free Process to Fabricate High Performance Silicon/Graphite Composite Anode

by Chen Fang, Haiqing Xiao, Tianyue Zheng, Hua Bai and Gao Liu

J. Compos. Sci. 2021, 5(7), 188; https://doi.org/10.3390/jcs5070188 - 17 Jul 2021

Cited by 9 | Viewed by 3839

Abstract

Cycling stability is a key challenge for application of silicon (Si)-based composite anodes as the severe volume fluctuation of Si readily leads to fast capacity fading. The binder is a crucial component of the composite electrodes. Although only occupying a small amount of [...] Read more.

Cycling stability is a key challenge for application of silicon (Si)-based composite anodes as the severe volume fluctuation of Si readily leads to fast capacity fading. The binder is a crucial component of the composite electrodes. Although only occupying a small amount of the total composite mass, the binder has major impact on the long-term electrochemical performance of Si-based anodes. In recent years, water-based binders including styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) have attracted wide research interest as eco-friendly and low-cost alternatives for the conventional poly(vinylidene difluoride) (PVDF) binder in Si anodes. In this study, Si-based composite anodes are fabricated by simple solid mixing of the active materials with subsequent addition of SBR and CMC binders. This approach bypasses the use of toxic and expansive organic solvents. The factors of binder, silicon, and graphite materials have been systematically investigated. It is found that the retained capacities of the anodes are more than 440 mAh/g after 400 cycles. These results indicate that organic solvent free process is a facile strategy for producing high performance silicon/graphite composite anodes. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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16 pages, 7954 KiB

Open AccessArticle

Effect of Wood Fiber Surface Treatment on the Properties of Recycled HDPE/Maple Fiber Composites

by Roberto C. Vázquez Fletes and Denis Rodrigue

J. Compos. Sci. 2021, 5(7), 177; https://doi.org/10.3390/jcs5070177 - 7 Jul 2021

Cited by 12 | Viewed by 3387

Abstract

This work reports on the production and characterization of recycled high density polyethylene (R-HDPE) composites reinforced with maple fibers. The composites were produced by a simple dry-blending technique followed by compression molding. Furthermore, a fiber surface treatment was performed using a coupling agent [...] Read more.

This work reports on the production and characterization of recycled high density polyethylene (R-HDPE) composites reinforced with maple fibers. The composites were produced by a simple dry-blending technique followed by compression molding. Furthermore, a fiber surface treatment was performed using a coupling agent (maleated polyethylene, MAPE) in solution. FTIR, TGA/DTG, and density analyses were performed to confirm any changes in the functional groups on the fiber surface, which was confirmed by SEM-EDS. As expected, the composites based on treated fiber (TC) showed improved properties compared to composites based on untreated fiber (UC). In particular, MAPE was shown to substantially improve the polymer–fiber interface quality, thus leading to better mechanical properties in terms of tensile modulus (23%), flexural modulus (54%), tensile strength (26%), and flexural strength (46%) as compared to the neat matrix. The impact resistance also increased by up to 87% for TC as compared to UC. In addition, the maximum fiber content to produce good parts increased from 15 to 75 wt% when treated fiber was used. These composites can be seen as sustainable materials and possible alternatives for the development of low-cost building/construction/furniture applications. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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8 pages, 4451 KiB

Open AccessArticle

The Effect of Pre-Bond Contamination by Thermal Degradation and De-Icing Fluid on the Tensile Strength of Scarf Composite Bonded Joints

by Konstantinos Tserpes and Elli Moutsompegka

J. Compos. Sci. 2021, 5(7), 168; https://doi.org/10.3390/jcs5070168 - 28 Jun 2021

Cited by 1 | Viewed by 1696

Abstract

The synergistic effect of pre-bond contamination by thermal degradation and de-icing fluid on the tensile behavior of scarf composite bonded joints has been investigated experimentally. The contamination types considered are related to the repair process of composite aircraft structures. Three contamination scenarios have [...] Read more.

The synergistic effect of pre-bond contamination by thermal degradation and de-icing fluid on the tensile behavior of scarf composite bonded joints has been investigated experimentally. The contamination types considered are related to the repair process of composite aircraft structures. Three contamination scenarios have been considered: namely, thermal degradation (TD) and a combination of thermal degradation with two different levels of de-icing fluid (TD+DI1 and TD+DI2). DI2 is more severe than DI1. Contamination has been applied to one of the adherents while the other one has been intentionally left intact. Tension tests have been conducted on single-lap shear specimens. The experimental results were compared with the reference samples (REF) showing an increase in tensile strength for the TD specimens and a decrease in tensile strength for the TD+DI1 and TD+DI2 specimens. After the tension tests, the failure surfaces were evaluated to get a better insight of the failure mechanisms of the bondline and to assess the effect of contamination. The TD specimens presented an increased cohesive failure which is consistent with the increase of the failure load, while the combined contamination caused the failure of the composite adherents which again is consistent with the decrease of tensile strength of the scarf specimens. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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12 pages, 2337 KiB

Open AccessArticle

Study on Indium (III) Oxide/Aluminum Thermite Energetic Composites

by Pierre Gibot and Estelle Puel

J. Compos. Sci. 2021, 5(7), 166; https://doi.org/10.3390/jcs5070166 - 26 Jun 2021

Cited by 5 | Viewed by 2595

Abstract

Thermites or composite energetic materials are mixtures made of fuel and oxidizer particles at micron-scale. Thermite reactions are characterized by high adiabatic flame temperatures (>1000 °C) and high heats of reaction (>kJ/cm³), sometimes combined with gas generation. These properties strongly depend [...] Read more.

Thermites or composite energetic materials are mixtures made of fuel and oxidizer particles at micron-scale. Thermite reactions are characterized by high adiabatic flame temperatures (>1000 °C) and high heats of reaction (>kJ/cm³), sometimes combined with gas generation. These properties strongly depend on the chemical nature of the couple of components implemented. The present work focuses on the use of indium (III) oxide nanoparticles as oxidizer in the elaboration of nanothermites. Mixed with an aluminum nanopowder, heat of reaction of the resulting Al/In₂O₃ energetic nanocomposite was calculated and its reactive performance (sensitivity thresholds regarding different stimuli (impact, friction, and electrostatic discharge) and combustion velocity examined. The Al/In₂O₃ nanothermite, whose heat of reaction was determined of about 11.75 kJ/cm³, was defined as insensitive and moderately sensitive to impact and friction stimuli and extreme sensitive to spark with values >100 N, 324 N, and 0.31 mJ, respectively. The spark sensitivity was decreased by increasing In₂O₃ oxidizer (27.71 mJ). The combustion speed in confined geometries experiments was established near 500 m/s. The nature of the oxidizer implemented herein within a thermite formulation is reported for the first time. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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22 pages, 10911 KiB

Open AccessArticle

Stress-Strain Behaviour and Mechanical Strengths of Concrete Incorporating Mixed Recycled Plastics

by Mahmoud Abu-Saleem, Yan Zhuge, Reza Hassanli, Mark Ellis, Md Mizanur Rahman and Peter Levett

J. Compos. Sci. 2021, 5(6), 146; https://doi.org/10.3390/jcs5060146 - 30 May 2021

Cited by 14 | Viewed by 4397

Abstract

Different types of recycled plastic have been used in concrete and most studies have focused on the behaviour of a single type of plastic. However, separating plastic wastes increases the cost and time of processing. To tackle this problem, this research presents an [...] Read more.

Different types of recycled plastic have been used in concrete and most studies have focused on the behaviour of a single type of plastic. However, separating plastic wastes increases the cost and time of processing. To tackle this problem, this research presents an experimental investigation to determine the effect of incorporating different combinations of three types of recycled plastic waste aggregates—Polyethylene terephthalate (PET), High Density Polyethylene (HDPE) and Polypropylene (PP)—at different replacement ratios of coarse aggregate on physical and mechanical properties of concrete. The combinations include two plastic types at 10% and 20% replacement ratios and three plastic types at 15% and 30% replacement ratios. The performance of the plastic concrete was assessed based on various physical and mechanical properties including workability, fresh and dry densities, air content, compressive, indirect tensile and flexural strengths, modulus of elasticity, stress-strain behaviour and ultrasonic pulse velocity. It is found that the workability of Mixed Recycled Plastic Concrete (MRPC) at a low replacement rate is independent of the type of plastic. The minimum reduction in the compressive strength, indirect tensile and modulus of elasticity were achieved by R3 (PET + PP) at 10% replacement, while R5 (HDPE + PP) at 10% replacement achieved the highest flexural strength and ultrasonic pulse velocity values. The findings suggest that the mixed recycled plastics have a good possibility to partially replace coarse aggregates in concrete which will benefit the plastics recycling community and environment. Furthermore, the study will provide guidance to the concrete industry concerning the effect of the implementation of unsorted mixed types of plastic as coarse aggregates in the production of concrete. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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11 pages, 1840 KiB

Open AccessArticle

Controlled Magnetic Isolation and Decoupling of Perpendicular FePt Films by Capping Ultrathin Cu(002) Nano-Islands

by Da-Hua Wei, Ji-Hong Chang, Chi-Chun Hsu, Cheng-Jie Yang, Yuan-Chang Liang, Chung-Li Dong and Yeong-Der Yao

J. Compos. Sci. 2021, 5(6), 140; https://doi.org/10.3390/jcs5060140 - 21 May 2021

Cited by 3 | Viewed by 2163

Abstract

This study investigated the ultrathin Cu(002) capping nano-island effects on the magnetic characterizations and microstructure of epitaxial FePt(001) films directly fabricated on MgO(001) substrates at the relatively low temperature of 300 °C via electron-beam deposition. The enhancement of the coercivity is attributed to [...] Read more.

This study investigated the ultrathin Cu(002) capping nano-island effects on the magnetic characterizations and microstructure of epitaxial FePt(001) films directly fabricated on MgO(001) substrates at the relatively low temperature of 300 °C via electron-beam deposition. The enhancement of the coercivity is attributed to the lowered exchange coupling of FePt magnetic grains that begun from Cu atom behavior of spreading in many directions mainly along grain boundaries due to its lower surface energy than that of pure Fe or Pt. The measurement of angular-dependent coercivity shows a tendency of a domain-wall motion shift toward the rotation of the reverse-domain type upon the thickness of the Cu capping nano-island layer atop the FePt films. The intergranular interaction was clarified by the Kelly–Henkel plot, which indicated that there was strong exchange coupling (positive δM) between neighboring grains in the FePt continuous films without Cu capping nano-islands. On the other hand, a negative δM value was gained when the FePt films were capped with a Cu(002) single layer, indicating that the Cu capping layer can be used to control the strength of intergrain exchange coupling between the adjacent FePt grains and thicker Cu(002) capping nano-islands toward magnetic isolation; thus, there was an existence of dipole interaction in our designed Cu/FePt composite structure of stacked films. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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25 pages, 53188 KiB

Open AccessArticle

Parametric Optimization of Isotropic and Composite Axially Symmetric Shells Subjected to External Pressure and Twisting

by Marek Barski, Paweł J. Romanowicz, Małgorzata Chwał and Adam Stawiarski

J. Compos. Sci. 2021, 5(5), 128; https://doi.org/10.3390/jcs5050128 - 12 May 2021

Cited by 1 | Viewed by 1813

Abstract

The present paper is devoted to the problem of the optimal design of thin-walled composite axially symmetric shells with respect to buckling resistance. The optimization problem is formulated with the following constraints: namely, all analyzed shells have identical capacity and volume of material. [...] Read more.

The present paper is devoted to the problem of the optimal design of thin-walled composite axially symmetric shells with respect to buckling resistance. The optimization problem is formulated with the following constraints: namely, all analyzed shells have identical capacity and volume of material. The optimization procedure consists of four steps. In the first step, the initial calculations are made for cylindrical shells with non-optimal orientation of layers and these results are used as the reference for optimization. Next, the optimal orientations of layers for cylindrical shapes are determined. In the third step, the optimal geometrical shape of a middle surface with a constant thickness is determined for isotropic material. Finally, for the assumed shape of the middle surface, the optimal fiber orientation angle θ of the composite shell is appointed. Such studies were carried for three cases: pure external pressure, pure twisting, and combined external pressure with twisting. In the case of shells made of isotropic material the obtained results are compared with the optimal structure of uniform stability, where the analytical Shirshov’s local stability condition is utilized. In the case of structures made of composite materials, the computations are carried out for two different materials, where the ratio of E₁/E₂ is equal to 17.573 and 3.415. The obtained benefit from optimization, measured as the ratio of critical load multiplier computed for reference shell and optimal structure, is significant. Finally, the optimal geometrical shapes and orientations of the layers for the assumed loadings is proposed. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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10 pages, 3218 KiB

Open AccessArticle

In Vivo Effects of Two In-Office Vital Tooth Bleaching Systems on Enamel Permeability

by Angelica Bertacci, Gianfranco Ulian, Daniele Moro, Stefano Chersoni and Giovanni Valdrè

J. Compos. Sci. 2021, 5(4), 98; https://doi.org/10.3390/jcs5040098 - 4 Apr 2021

Viewed by 2055

Abstract

Tooth bleaching is a common treatment for the amelioration of the aesthetic of discoloured teeth. In this context, there are two common approaches that employ concentrated solutions (30–40 wt.%) of either hydrogen peroxide or carbamide peroxide as bleaching agents. However, there is an [...] Read more.

Tooth bleaching is a common treatment for the amelioration of the aesthetic of discoloured teeth. In this context, there are two common approaches that employ concentrated solutions (30–40 wt.%) of either hydrogen peroxide or carbamide peroxide as bleaching agents. However, there is an ongoing debate on the possible adverse effects of these different treatments on tooth health, such as variation of the enamel structure, surface morphology, and chemistry, which also affect tooth sensitivity. In the present work, a study on the effect of the two bleaching agents, a 35 wt.% solution of hydrogen peroxide and a 30 wt.% solution of carbamide peroxide, on the permeability and surface morphology of enamel is reported. The investigation was carried out on replicas of incisors obtained after different treatment times and for several patients, employing scanning electron microscopy to study the morphological features of the treated teeth. The significance of the analytical study was corroborated by a statistical analysis of the results. The collected data suggest that hydrogen peroxide treatment increases the enamel permeability, and this could be related with tooth sensitivity, whereas the carbamide peroxide solution increases the formation of precipitates on the tooth enamel. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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18 pages, 11221 KiB

Open AccessArticle

Assessment of Replacement of Metal Parts by BFRP Composites into a Highly Efficient Electrical Prototype

by Rosa Marat-Mendes, Diogo Ribeira and Luís Reis

J. Compos. Sci. 2021, 5(4), 95; https://doi.org/10.3390/jcs5040095 - 1 Apr 2021

Viewed by 2109

Abstract

This work intends to evaluate the use of epoxy composite materials reinforced with basalt fibers as replacement to metallic mechanical parts of a highly efficient electrical prototype. The analysis of the behavior of the original metallic bracket was made and an optimization process [...] Read more.

This work intends to evaluate the use of epoxy composite materials reinforced with basalt fibers as replacement to metallic mechanical parts of a highly efficient electrical prototype. The analysis of the behavior of the original metallic bracket was made and an optimization process was carried out in order to achieve the most suitable geometry and stacking sequence if produced in composite material. Finite element analysis using Siemens NX12 and experimental tests to the produced composite part were performed in order to access it. It was verified that the total weight of the composite part shows a 45% reduction. The composite part shows a higher deformation than the metallic one due to basalt fiber’s higher flexibility. However, the advantages added by the new component largely compensate for the disadvantages that may have been added without compromising its performance. Obtained results show that the use of basalt fiber reinforced composites as the material of mechanical parts of a highly efficient electrical prototype that is a good alternative. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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27 pages, 5222 KiB

Open AccessArticle

Multi-Objective Optimization of Functionally Graded Beams Using a Genetic Algorithm with Non-Dominated Sorting

by Chih-Ping Wu and Kuan-Wei Li

J. Compos. Sci. 2021, 5(4), 92; https://doi.org/10.3390/jcs5040092 - 30 Mar 2021

Cited by 8 | Viewed by 1886

Abstract

A mixed layer-wise (LW) higher-order shear deformation theory (HSDT) is developed for the thermal buckling analysis of simply-supported, functionally graded (FG) beams subjected to a uniform temperature change. The material properties of the FG beam are assumed to be dependent on the thickness [...] Read more.

A mixed layer-wise (LW) higher-order shear deformation theory (HSDT) is developed for the thermal buckling analysis of simply-supported, functionally graded (FG) beams subjected to a uniform temperature change. The material properties of the FG beam are assumed to be dependent on the thickness and temperature variables, and the effective material properties are estimated using either the rule of mixtures or the Mori–Tanaka scheme. The results shown in the numerical examples indicate the mixed LW HSDT solutions for critical temperature change parameters are in excellent agreement with the accurate solutions available in the literature. A multi-objective optimization of FG beams is presented to maximize the critical temperature change parameters and to minimize their total mass using a non-dominated sorting-based genetic algorithm. Some specific forms for the volume fractions of the constituents of the FG beam are assumed in advance, such as the one- and three-parameter power-law functions. The former is used in the thermal buckling analysis of the FG beams for comparison purposes, and the latter is used in their optimal design. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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13 pages, 4273 KiB

Open AccessArticle

S-N Curve Characterisation for Composite Materials and Prediction of Remaining Fatigue Life Using Damage Function

by Ho Sung Kim and Saijie Huang

J. Compos. Sci. 2021, 5(3), 76; https://doi.org/10.3390/jcs5030076 - 7 Mar 2021

Cited by 6 | Viewed by 5856

Abstract

S-N curve characterisation and prediction of remaining fatigue life are studied using polyethylene terephthalate glycol-modified (PETG). A new simple method for finding a data point at the lowest number of cycles for the Kim and Zhang S-N curve model is proposed to avoid [...] Read more.

S-N curve characterisation and prediction of remaining fatigue life are studied using polyethylene terephthalate glycol-modified (PETG). A new simple method for finding a data point at the lowest number of cycles for the Kim and Zhang S-N curve model is proposed to avoid the arbitrary choice of loading rate for tensile testing. It was demonstrated that the arbitrary choice of loading rate may likely lead to an erroneous characterisation for the prediction of the remaining fatigue life. The previously proposed theoretical method for predicting the remaining fatigue life of composite materials involving the damage function was verified at a stress ratio of 0.4 for the first time. Both high to low and low to high loadings were conducted for predicting the remaining fatigue lives and a good agreement between predictions and experimental results was found. Fatigue damage consisting of cracks and whitening is described. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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19 pages, 4752 KiB

Open AccessArticle

Optimizing Precursors and Reagents for the Development of Alkali-Activated Binders in Ambient Curing Conditions

by Dhruv Sood and Khandaker M. Anwar Hossain

J. Compos. Sci. 2021, 5(2), 59; https://doi.org/10.3390/jcs5020059 - 20 Feb 2021

Cited by 12 | Viewed by 2720

Abstract

Alkali-activated binders (AABs) are developed through the activation of aluminosilicate-rich materials using alkaline reagents. The characteristics of AABs developed using a novel dry-mixing technique incorporating powder-based reagents/activators are extensively explored. A total of forty-four binder mixes are assessed in terms of their fresh [...] Read more.

Alkali-activated binders (AABs) are developed through the activation of aluminosilicate-rich materials using alkaline reagents. The characteristics of AABs developed using a novel dry-mixing technique incorporating powder-based reagents/activators are extensively explored. A total of forty-four binder mixes are assessed in terms of their fresh and hardened state properties. The influence of mono/binary/ternary combinations of supplementary cementitious materials (SCMs)/precursors and different types/combinations/dosages of powder-based reagents on the strength and workability properties of different binder mixes are assessed to determine the optimum composition of precursors and the reagents. The binary (55% fly ash class C and 45% ground granulated blast furnace slag) and ternary (25% fly ash class C, 35% fly ash class F and 40% ground granulated blast furnace slag) binders with reagent-2 (calcium hydroxide and sodium sulfate = 2.5:1) exhibited desired workability and 28-day compressive strengths of 56 and 52 MPa, respectively. Microstructural analyses (in terms of SEM/EDS and XRD) revealed the formation of additional calcium aluminosilicate hydrate with sodium or mixed Ca/Na compounds in binary and ternary binders incorporating reagent-2, resulting in higher compressive strength. This research confirms the potential of producing powder-based cement-free green AABs incorporating binary/ternary combinations of SCMs having the desired fresh and hardened state properties under ambient curing conditions. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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18 pages, 8414 KiB

Open AccessArticle

Mechanical and FEA-Assisted Characterization of Fused Filament Fabricated Triply Periodic Minimal Surface Structures

by Nikolaos Kladovasilakis, Konstantinos Tsongas and Dimitrios Tzetzis

J. Compos. Sci. 2021, 5(2), 58; https://doi.org/10.3390/jcs5020058 - 17 Feb 2021

Cited by 42 | Viewed by 5528

Abstract

This paper investigates the mechanical behavior of additive manufactured Triply Periodic Minimal Surface (TPMS) structures, such as Gyroid, Schwarz Diamond and Schwarz Primitive. Fused Filament Fabrication (FFF) technique was utilized in order to fabricate lattice structures with different relative densities, at 10%, 20% [...] Read more.

This paper investigates the mechanical behavior of additive manufactured Triply Periodic Minimal Surface (TPMS) structures, such as Gyroid, Schwarz Diamond and Schwarz Primitive. Fused Filament Fabrication (FFF) technique was utilized in order to fabricate lattice structures with different relative densities, at 10%, 20% and 30%, using Polylactic acid (PLA). The test specimens were formed by structural TPMS unit cells and they were tested under quasi-static compression. A finite element analysis (FEA) was performed in order to predict their stress-strain behavior and compare with the experimental results. The results revealed that each architecture influences the mechanical properties of the structure differently depending on the impact of size effect. The structures were designed as sandwich structures (with a top and bottom plate) to avoid significant deterioration of the mechanical behavior, due to the size effect and this was achieved at high relative densities. The Schwarz Diamond structure demonstrated the highest mechanical strength compared with the other architectures, while the Gyroid structure also revealed a similar mechanical performance. In addition, Schwarz Primitive structure showed increased energy absorption especially during plastic deformation. The overall results revealed that the integrity of the mechanical properties of the studied TPMS FFF printed structures deteriorates, as the relative density of the structures decreases. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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56 pages, 20189 KiB

Open AccessArticle

On the Use of Molecular Dynamics Simulations for Elucidating Fine Structural, Physico-Chemical and Thermomechanical Properties of Lignocellulosic Systems: Historical and Future Perspectives

by Krishnamurthy Prasad, Mostafa Nikzad, Shammi Sultana Nisha and Igor Sbarski

J. Compos. Sci. 2021, 5(2), 55; https://doi.org/10.3390/jcs5020055 - 10 Feb 2021

Cited by 6 | Viewed by 3897

Abstract

The use of Molecular Dynamics (MD) simulations for predicting subtle structural, thermomechanical and related characteristics of lignocellulosic systems is studied. A historical perspective and the current state of the art are discussed. The use of parameterised MD force fields, scaling up simulations via [...] Read more.

The use of Molecular Dynamics (MD) simulations for predicting subtle structural, thermomechanical and related characteristics of lignocellulosic systems is studied. A historical perspective and the current state of the art are discussed. The use of parameterised MD force fields, scaling up simulations via high performance computing and intrinsic molecular mechanisms influencing the mechanical, thermal and chemical characteristics of lignocellulosic systems and how these can be predicted and modelled using MD is shown. Individual discussions on the MD simulations of the lignin, cellulose, lignin-carbohydrate complex (LCC) and how MD can elucidate the role of water on the surface and microstructural characteristics of these lignocellulosic systems is shown. In addition, the use of MD for unearthing molecular mechanisms behind lignin-enzyme interactions during precipitation processes and the deforming/structure weakening brought about by cellulosic interactions in some lignocellulosic systems is both predicted and quantified. MD results from relatively smaller systems comprised of several hundred to a few thousand atoms and massive multi-million atom systems are both discussed. The versatility and effectiveness of MD based on its ability to provide viable predictions from both smaller and massive starting systems is presented in detail. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2021)

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