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J. Compos. Sci., Volume 3, Issue 2 (June 2019)

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Open AccessArticle
Fiber-Reinforced Composite Sandwich Structures by Co-Curing with Additive Manufactured Epoxy Lattices
J. Compos. Sci. 2019, 3(2), 53; https://doi.org/10.3390/jcs3020053 (registering DOI)
Received: 31 March 2019 / Revised: 5 May 2019 / Accepted: 13 May 2019 / Published: 16 May 2019
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Abstract
In this paper, a new process of joining additive manufactured (AM) lattice structures and carbon fiber-reinforced plastics (CFRPs) to manufacture hybrid lattice sandwich structures without secondary bonding is investigated. Multiple variations of lattice structures are designed and 3D printed using Digital Light Synthesis [...] Read more.
In this paper, a new process of joining additive manufactured (AM) lattice structures and carbon fiber-reinforced plastics (CFRPs) to manufacture hybrid lattice sandwich structures without secondary bonding is investigated. Multiple variations of lattice structures are designed and 3D printed using Digital Light Synthesis (DLS) and a two-stage (B-stage) epoxy resin system. The resulting lattice structures are only partially cured and subsequently thermally co-cured with pre-impregnated carbon fiber reinforcement. The mechanical properties of the additive manufactured lattice structures are characterized by compressive tests. Furthermore, the mechanical properties of hybrid lattice sandwich structures are assessed by flexural beam testing. From compressive testing of the additive manufactured lattice structures, high specific strength can be ascertained. The mechanical behavior shows these lattice structures to be suitable for use as sandwich core materials. Flexural beam testing of hybrid lattice sandwich structures shows high strength and stiffness. Furthermore, the strength of the co-cured bond interface is high enough to surpass the strength of the lattice core. Full article
(This article belongs to the Special Issue Additive Manufacturing of Polymeric and Ceramic Composites)
Open AccessArticle
Analysis of the Degradation During Melt Processing of PLA/Biosilicate® Composites
J. Compos. Sci. 2019, 3(2), 52; https://doi.org/10.3390/jcs3020052 (registering DOI)
Received: 9 April 2019 / Revised: 9 May 2019 / Accepted: 13 May 2019 / Published: 16 May 2019
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Abstract
Poly (lactic acid) (PLA)/bioactive composites are emerging as new biomaterials since it is possible to combine stiffness, mechanical resistance, and bioactive character of the bioglasses with conformability and bioabsorption of the PLA. In this study, PLA/Biosilicate® composites were prepared using a melt-processing [...] Read more.
Poly (lactic acid) (PLA)/bioactive composites are emerging as new biomaterials since it is possible to combine stiffness, mechanical resistance, and bioactive character of the bioglasses with conformability and bioabsorption of the PLA. In this study, PLA/Biosilicate® composites were prepared using a melt-processing route. The processability and properties were evaluated aiming to produce composites with bioactive properties. Two different PLA (PLA 2003D and PLA 4043D) were tested with the addition of 1 wt. % of Biosilicate®. Both materials presented a huge reduction in melt viscosity after internal mixer processing. The degradation effects of the addition of Biosilicate® in the PLAs matrices were evaluated using zeta potential tests that showed a very high liberation of ions, which catalyzes PLA thermo-oxidative reactions. To understand the extension of degradation effects during the processing, the composites were characterized using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), gel permeation chromatography (GPC), and rheological tests. GPC results showed that PLA with the lowest residual acid content (RAC), PLA 2003D, presented higher thermal stability, higher molecular weight, and viscosity baseline compared to PLA 4043D. The composites showed a significant decrease in molecular weight for both PLA with the addition of Biosilicate®. TGA results showed that Biosilicate® might have reduced the activation energy to initiate thermodegradation reactions in PLAs and it occasioned a reduction in the Tonset by almost 40 °C. The DSC results showed that severe matrix degradation and the presence of bioglass did not significantly affect glass transition temperature (Tg), melting temperature (Tm) and crystallinity of PLAs, but it influenced cold crystallization peak (Tcc). In this way, the type of PLA used influences the processability of this material, which can make the production of filaments of this material for 3D printing unfeasible. Full article
(This article belongs to the Special Issue Nanocomposites for Biomedical Implants and Tissue Engineering)
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Open AccessReview
Polymer Composites Reinforced with Natural Fibers and Nanocellulose in the Automotive Industry: A Short Review
J. Compos. Sci. 2019, 3(2), 51; https://doi.org/10.3390/jcs3020051
Received: 8 April 2019 / Revised: 27 April 2019 / Accepted: 6 May 2019 / Published: 13 May 2019
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Abstract
Environmental concerns and cost reduction have encouraged the use of natural fillers as reinforcement in polymer composites. Currently, a wide variety of reinforcement, such as natural fibers and nanocellulose, are used for this purpose. Composite materials with natural fillers have not only met [...] Read more.
Environmental concerns and cost reduction have encouraged the use of natural fillers as reinforcement in polymer composites. Currently, a wide variety of reinforcement, such as natural fibers and nanocellulose, are used for this purpose. Composite materials with natural fillers have not only met the environmental appeal, but also contribute to developing low-density materials with improved properties. The production of natural fillers is unlimited around the world, and many species are still to be discovered. Their processing is considered beneficial since the natural fillers do not cause corrosion or great wear of the equipment. For these reasons, polymer reinforced with natural fillers has been considered a good alternative for obtaining ecofriendly materials for several applications, including the automotive industry. This review explores the use of natural fillers (natural fibers, cellulose nanocrystals, and nanofibrillated cellulose) as reinforcement in polymer composites for the automotive industry. Full article
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Open AccessArticle
Fabrication of Nanostructured Kaolinite Doped Composite Films from Silicone Rubber with Enhanced Properties
J. Compos. Sci. 2019, 3(2), 50; https://doi.org/10.3390/jcs3020050
Received: 5 April 2019 / Revised: 6 May 2019 / Accepted: 8 May 2019 / Published: 12 May 2019
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Abstract
Naturally occurring nanomaterials are finding growing interests in tailoring properties of engineering polymers for advanced applications. The objective of this study was to develop environment-friendly nanocomposite films by reinforcing kaolinite nanofillers (1–10 wt%) in silicone rubber (SR) matrix using a simple solvent casting [...] Read more.
Naturally occurring nanomaterials are finding growing interests in tailoring properties of engineering polymers for advanced applications. The objective of this study was to develop environment-friendly nanocomposite films by reinforcing kaolinite nanofillers (1–10 wt%) in silicone rubber (SR) matrix using a simple solvent casting technique. Kaolinite-reinforced films showed substantial improvement in mechanical (tensile strength, Young’s modulus, and elongation at break) and thermal properties at very low filler loading (5 wt%). The improvement of solvent resistance nature of the fabricated films was another critical aspect of this study. Unfilled SR film showed ~19% weight loss when immersed in toluene for 4 h at 25 °C, whereas only ~4% weight loss was recorded in the case of 5% (w/w) kaolinite loaded film. Therefore, kaolinite has the potential to bring significant improvement in the properties of SR. This study indicates that there is plenty of room at the bottom for proper utilization of the potential of kaolinite for developing SR-based composite materials for potential applications in many industries, such as textile, household cleaning, construction, electronics, automotive, medical, etc. Full article
(This article belongs to the Special Issue Sustainable Rubber Composites)
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Open AccessArticle
Validating a Failure Surface Developed for ABS Fused Filament Fabrication Parts through Complex Loading Experiments
J. Compos. Sci. 2019, 3(2), 49; https://doi.org/10.3390/jcs3020049
Received: 1 April 2019 / Revised: 18 April 2019 / Accepted: 6 May 2019 / Published: 10 May 2019
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Abstract
Fused Filament Fabrication (FFF) is arguably the most widely available additive manufacturing technology at the moment. Offering the possibility of producing complex geometries in a compressed product development cycle and in a plethora of materials, it has gradually started to become attractive to [...] Read more.
Fused Filament Fabrication (FFF) is arguably the most widely available additive manufacturing technology at the moment. Offering the possibility of producing complex geometries in a compressed product development cycle and in a plethora of materials, it has gradually started to become attractive to multiple industrial segments, slowly being implemented in diverse applications. However, the high anisotropy of parts developed through this technique renders failure prediction difficult. The proper performance of the part, or even the safety of the final user, cannot be guaranteed under demanding mechanical requirements. This problem can be tackled through the development of a failure envelope that allows engineers to predict failure by using the knowledge of the stress state of the part. Previous research by the authors developed a failure envelope for acrylonitrile butadiene styrene (ABS) based, Fused Filament Fabrication (FFF) parts by use of a criterion that incorporates stress interactions. This work validates the first quadrant of the envelope by performing uniaxial tensile tests with coupons produced with a variety of raster angles, creating a combined loading stress state in the localized coordinate system. Results show the safe zone encompassed by the failure envelope proved adequate. Full article
(This article belongs to the Special Issue Additive Manufacturing of Polymeric and Ceramic Composites)
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Open AccessArticle
Butyl Rubber-Based Composite: Thermal Degradation and Prediction of Service Lifetime
J. Compos. Sci. 2019, 3(2), 48; https://doi.org/10.3390/jcs3020048
Received: 11 April 2019 / Revised: 25 April 2019 / Accepted: 26 April 2019 / Published: 5 May 2019
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Abstract
Butyl rubber-based composite (BRC) is one of the most popular materials for the fabrication of protective gloves against chemical and mechanical risks. However, in many workplaces, such as metal manufacturing or automotive mechanical services, its mechanical hazards usually appear together with metalworking fluids [...] Read more.
Butyl rubber-based composite (BRC) is one of the most popular materials for the fabrication of protective gloves against chemical and mechanical risks. However, in many workplaces, such as metal manufacturing or automotive mechanical services, its mechanical hazards usually appear together with metalworking fluids (MWFs). The presence of these contaminants, particularly at high temperatures, could modify its properties due to the scission, the plasticization and the crosslinking of the polymer network and thus lead to severe modification of the mechanical and physicochemical properties of material. This work aims to determine the effect of temperature and a metalworking fluid on the mechanical behavior of butyl rubber composite, dealing with crosslinking density, cohesion forces and the elastic constant of BRC, based on Mooney–Rivlin’s theory. The effect of temperature with and without MWFs on the thermo-dynamical properties and morphology of butyl membranes was also investigated. The prediction of service lifetime was then evaluated from the extrapolation of the Arrhenius plot at different temperatures. Full article
(This article belongs to the Special Issue Durability of Composites Under Severe Environmental Conditions)
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Open AccessArticle
Defining Key Factors in Carbon Black-Filled NR/BR Compounds for Balancing Aircraft Tire Tread Properties
J. Compos. Sci. 2019, 3(2), 47; https://doi.org/10.3390/jcs3020047
Received: 11 March 2019 / Revised: 5 April 2019 / Accepted: 26 April 2019 / Published: 5 May 2019
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Abstract
Carbon black (CB) is the most common reinforcing filler used in aircraft tire tread formulations. For CB-reinforced natural rubber/butadiene rubber (NR/BR) compounds, material and processing parameters are important factors that need to be controlled, as they can influence both, processing as well as [...] Read more.
Carbon black (CB) is the most common reinforcing filler used in aircraft tire tread formulations. For CB-reinforced natural rubber/butadiene rubber (NR/BR) compounds, material and processing parameters are important factors that need to be controlled, as they can influence both, processing as well as the vulcanizate properties. It is essential to investigate and optimize the key elements, in order to achieve the target properties, while maintaining an acceptable trade-off for other characteristics. In the present study, the type of BR, mixer temperature, rotor speed, and filler mixing time were selected as input factors. A complete design of experiments (DOE) process was performed that comprised the following—two-level full factorial setup for initial screening, response surface method (RSM) for optimization, and confirmation runs for validation. This evaluation procedure was used to study the impact of factors and their interactions on the properties of CB-filled NR/BR compounds. From the DOE optimization which was later confirmed by the DOE validation, high rotor speed and long filler mixing time were the most significant factors in improving the Mooney viscosity, modulus at 300% elongation, hysteresis (tan delta), as well as in reducing the filler–filler interaction (Payne effect). In the case of tensile strength (TS) and abrasion resistance index (ARI), high rotor speed and long filler mixing time had an adverse effect, thus, causing a deterioration of these properties. Therefore, it is recommended to decrease the filler mixing time when combining it with high rotor speed. Full article
(This article belongs to the Special Issue Sustainable Rubber Composites)
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Open AccessArticle
Physical and Mechanical Properties of Binderless Particleboard Made from Steam-Pretreated Oil Palm Trunk Particles
J. Compos. Sci. 2019, 3(2), 46; https://doi.org/10.3390/jcs3020046
Received: 24 February 2019 / Revised: 10 April 2019 / Accepted: 26 April 2019 / Published: 2 May 2019
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Abstract
Formaldehyde emissions from conventional particleboards raise issues of health and safety. One of the potential solutions is binderless particleboards made without using synthetic adhesives. However, the physical and mechanical properties of untreated binderless particleboards are relatively poor compared to conventional particleboards. This research [...] Read more.
Formaldehyde emissions from conventional particleboards raise issues of health and safety. One of the potential solutions is binderless particleboards made without using synthetic adhesives. However, the physical and mechanical properties of untreated binderless particleboards are relatively poor compared to conventional particleboards. This research aims to reveal the potential of using steam pretreatment to improve binderless particleboard properties made from oil palm trunk. The oil palm trunk particles were treated with steam pretreatment for different durations of time (20, 40, 60 min). The chemical constituents of the treated and untreated particles were evaluated. The binderless particleboards were made from treated and untreated particles. In addition, panels using untreated oil palm trunk particles with 10% urea–formaldehyde resin were made and used as a comparison. The boards were evaluated according to European Standards. The results indicated that the hemicellulose and starch content gradually reduced with the progression of steam pretreatment. The physical and mechanical properties were improved by increasing steam pretreatment duration. The steam pretreatment was able to improve the properties of binderless particleboards made from oil palm trunk. However, the performance of steam-pretreated binderless particleboard in this study is not compatible with the particleboards made using 10% urea–formaldehyde. Full article
Open AccessArticle
Production and Characterization of Porous Polymeric Membranes of PLA/PCL Blends with the Addition of Hydroxyapatite
J. Compos. Sci. 2019, 3(2), 45; https://doi.org/10.3390/jcs3020045
Received: 21 March 2019 / Revised: 16 April 2019 / Accepted: 25 April 2019 / Published: 1 May 2019
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Abstract
Polymer membranes have been widely used in guided tissue regeneration (GTR) and guided bone regeneration (GBR). The literature recognizes that poly (lactic acid) (PLA)/poly (ε-caprolactone) (PCL) blends have better physicochemical properties and that a porous polymer surface facilitates cell adhesion and proliferation. In [...] Read more.
Polymer membranes have been widely used in guided tissue regeneration (GTR) and guided bone regeneration (GBR). The literature recognizes that poly (lactic acid) (PLA)/poly (ε-caprolactone) (PCL) blends have better physicochemical properties and that a porous polymer surface facilitates cell adhesion and proliferation. In addition, hydroxyapatite (HAp) incorporated into the polymer matrix promotes osteoinduction properties and osteoconduction to the polymer-ceramic biocomposite. Therefore, polymer membranes of PLA/PCL blend with the addition of HAp could be an alternative to be used in GBR. HAp was obtained by precipitation using the mixture of solutions of tetrahydrate calcium nitrate and monobasic ammonium phosphate salts. The porous membranes of the PLA/PCL (80/20) blend with the addition of HAp were obtained by solvent casting with a controlled humidity method, with the dispersion of HAp in chloroform and subsequent solubilization with the components of the blend. The solution was poured into molds for solvent evaporation under a controlled humidity atmosphere. The membranes showed the formation of pores on their surface, together with dispersed HAp particles. The results showed an increase in the surface porosity and improved bioactivity properties with the addition of HAp. Moreover, in biological studies with cell culture, it was possible to observe that the membranes with HAp have no cytotoxic effect on MC3T3 cells. These results indicate a promising use of the new biomaterial for GBR. Full article
(This article belongs to the Special Issue Nanocomposites for Biomedical Implants and Tissue Engineering)
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Open AccessArticle
Transverse Thermal Conductivity of Epoxy Carbon Fiber Prepreg Laminates with a Graphite Filled Matrix
J. Compos. Sci. 2019, 3(2), 44; https://doi.org/10.3390/jcs3020044
Received: 26 March 2019 / Revised: 18 April 2019 / Accepted: 24 April 2019 / Published: 1 May 2019
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Abstract
The thermal conductivity of carbon fiber reinforced polymers is crucial for new technologies and is used in cutting-edge technologies such as sensors, heated rollers and anti-icing of airplane wings. Researchers so far focused on coating conventional prepregs with thermally conductive materials to enhance [...] Read more.
The thermal conductivity of carbon fiber reinforced polymers is crucial for new technologies and is used in cutting-edge technologies such as sensors, heated rollers and anti-icing of airplane wings. Researchers so far focused on coating conventional prepregs with thermally conductive materials to enhance the transversal conductivity. Another strategy is followed in this study: Thermally conductive matrices filled with graphite platelets were processed by a laboratory prepreg line. Laminates produced from this type of prepregs show an enhancement in thermal conductivity by 3.3 times with a 20 vol% filler content relative to the matrix, and a 55 vol% fiber volume content in the laminate. The research shows that the incorporation of conductive particles in the matrix is more effective for increasing the conductivity than previous methods. Full article
Open AccessArticle
Manufacture of Hybrid Natural/Synthetic Fiber Woven Textiles for Use in Technical Biocomposites with Maximum Biobased Content
J. Compos. Sci. 2019, 3(2), 43; https://doi.org/10.3390/jcs3020043
Received: 27 February 2019 / Revised: 10 April 2019 / Accepted: 18 April 2019 / Published: 1 May 2019
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Abstract
This feasibility study investigates the flexural properties of biocomposites containing woven flax textiles (plain, twill, satin) and woven twill patterned hybrid textiles containing flax-/glass or flax-/carbon mixture for lightweight applications. Synthetic fibers are integrated as weft and flax fibers are integrated as warp [...] Read more.
This feasibility study investigates the flexural properties of biocomposites containing woven flax textiles (plain, twill, satin) and woven twill patterned hybrid textiles containing flax-/glass or flax-/carbon mixture for lightweight applications. Synthetic fibers are integrated as weft and flax fibers are integrated as warp yarns using a double-rapier weaving machine with a Jacquard attachment. The corresponding biocomposites are manufactured via vacuum infusion process using a biobased epoxy resin as a matrix. The manufactured biocomposites are analyzed with regard to their density and flexural properties. The results show that the use of hybrid textiles offers a promising solution for the manufacture of biocomposites with a higher biobased content and significantly improved flexural properties. Furthermore, the introduction of high-performance synthetic fibers in textiles enables the manufacture of biocomposites with an isotropic mechanical performance. Full article
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Open AccessArticle
Production and Mechanical Characterization of Graphene Micro-Ribbons
J. Compos. Sci. 2019, 3(2), 42; https://doi.org/10.3390/jcs3020042
Received: 22 February 2019 / Revised: 21 March 2019 / Accepted: 3 April 2019 / Published: 16 April 2019
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Abstract
Patterning of graphene into micro- and nano-ribbons allows for tunability in emerging fields such as flexible electronic and optoelectronic devices, and is gaining interest for the production of more efficient reinforcement for composite materials. In this work we fabricate micro-ribbons from graphene synthesized [...] Read more.
Patterning of graphene into micro- and nano-ribbons allows for tunability in emerging fields such as flexible electronic and optoelectronic devices, and is gaining interest for the production of more efficient reinforcement for composite materials. In this work we fabricate micro-ribbons from graphene synthesized via chemical vapor deposition (CVD) by combining ultraviolet (UV) photolithography and dry etching oxygen plasma treatments. We used Raman spectral imaging to confirm the effectiveness of the patterning procedure, which is suitable for large-area patterning of graphene on wafer-scale, and confirms that the quality of graphene remains unaltered. The produced micro-ribbons were finally transferred and embedded into a polymeric matrix and the mechanical response was investigated by in-situ mechanical investigation combining Raman spectroscopy and tensile/compressive tests. Full article
(This article belongs to the Special Issue Recent Advances in Graphene-based Nanocomposites)
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Open AccessArticle
Influence of Mixing Procedures, Rubber Treatment, and Fibre Additives on Rubcrete Performance
J. Compos. Sci. 2019, 3(2), 41; https://doi.org/10.3390/jcs3020041
Received: 14 February 2019 / Revised: 1 April 2019 / Accepted: 8 April 2019 / Published: 10 April 2019
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Abstract
This research extensively investigates how to enhance the mechanical performance of Rubcrete, aiming to move this type of concrete from the laboratory research level to a more practical use by the concrete industry. The effects of many different mixing procedures, chemical pre-treatments on [...] Read more.
This research extensively investigates how to enhance the mechanical performance of Rubcrete, aiming to move this type of concrete from the laboratory research level to a more practical use by the concrete industry. The effects of many different mixing procedures, chemical pre-treatments on the rubber particles, and the use of fibre additives, have been investigated for their impact upon Rubcrete workability, compressive strength, tensile strength, and flexural strength. The mixing procedure variables included mixing time and mixing order. The rubber pre-treatments utilized chemicals such as Sodium Hydroxide (NaOH), Hydrogen Peroxide (H2O2), Sulphuric acid (H2SO4), Calcium Chloride (CaCl2), Potassium Permanganate (KMnO4), Sodium Bisulphite (NaHsO3), and Silane Coupling Agent. Soaking rubber particles in tap water, or running them through water before mixing, were also tried as a pre-treatment of rubber particles. In addition, the effects of fibre additives such as steel fibres, polypropylene fibres, and rubber fibres, were assessed. X-ray photoelectron spectroscopy (XPS) analysis was utilised to examine some of the pre-treated rubber particles. The results showed that doubling the net mixing time of all mix constituents together enhanced the Rubcrete slump by an average of 22%, and the compressive strength by up to 8%. Mixing rubber with dry cement before adding to the mix increased the compressive strength by up to 3%. Pre-treatment using water was more effective than other chemicals in enhancing the Rubcrete workability. Regardless of the treatment material type, the longer the time of the treatment, the more cleaning of rubber occurred. Significant Rubcrete flexural strength increase occurred when using 1.5% fibre content of both steel fibre and polypropylene fibre. Full article
(This article belongs to the Special Issue Sustainable Rubber Composites)
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Open AccessReview
Structural Performance of Polyurethane Foam-Filled Building Composite Panels: A State-Of-The-Art
J. Compos. Sci. 2019, 3(2), 40; https://doi.org/10.3390/jcs3020040
Received: 8 March 2019 / Revised: 26 March 2019 / Accepted: 26 March 2019 / Published: 10 April 2019
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Abstract
Composite panels with polyurethane (PU) foam-core and facing materials, such as gypsum, engineered wood or some composite materials, are being used as structural members in building construction. This paper reviews and summarises major research developments, and provides an updated review of references on [...] Read more.
Composite panels with polyurethane (PU) foam-core and facing materials, such as gypsum, engineered wood or some composite materials, are being used as structural members in building construction. This paper reviews and summarises major research developments, and provides an updated review of references on the structural performance of foam-filled building composite panels from 1998 to 2017. The review revealed that previous studies on the structural performance of foam-filled building composite panels could be categorised into five themes; namely, energy absorption and dynamic behaviour; bending and shear behaviour, edgewise and flatwise compressive/tensile behaviour; delamination/deboning issues; and finally some miscellaneous issues. These categories comprise approximately 30%, 40%, 11%, 11% and 8% of related studies over the last two decades, respectively. Also, over the past five years, the number of relevant studies has increased by ~400% relative to the previous similar periods, indicating the attention and focus of researchers to the importance of the structural performance of foam-filled composite panels. Full article
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Open AccessArticle
pH-Triggered Interfacial Interaction of Kaolinite/Chitosan Nanocomposites with Anionic Azo Dye
J. Compos. Sci. 2019, 3(2), 39; https://doi.org/10.3390/jcs3020039
Received: 21 February 2019 / Revised: 25 March 2019 / Accepted: 28 March 2019 / Published: 8 April 2019
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Abstract
Advanced engineering of naturally occurring materials opens new doors in nanoscience and nanotechnology for the separation and/or removal of environmental hazards. Here, a series of nanocomposites containing kaolinite and chitosan varying in the range of 20 to 80% (w/w) kaolinite were used for [...] Read more.
Advanced engineering of naturally occurring materials opens new doors in nanoscience and nanotechnology for the separation and/or removal of environmental hazards. Here, a series of nanocomposites containing kaolinite and chitosan varying in the range of 20 to 80% (w/w) kaolinite were used for the adsorptive removal of a reactive textile dye, Remazol Red, from an aqueous solution. Batch experiments were carried out to investigate the effects of pH, contact time, and initial dye concentration on the adsorption capacity. Nanocomposites containing 80% kaolinite (w/w) and 20% chitosan (w/w), i.e., NK80C20, showed an equilibrium adsorption capacity of 371.8 mg/g at pH 2.5, which was 5.2 times higher than that of commercial activated charcoal. Moreover, NK80C20 was regenerated instantly up to 99.9% at pH 10. Therefore, NK80C20 can be effectively utilized as a potential adsorbent for the separation of Remazol Red and homologous azo dyes from industrial effluents. We expect that the findings from this study will play a vital role in environmental research leading to advanced applications in water purification. Full article
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Open AccessArticle
Nucleation of the β-polymorph in Composites of Poly(propylene) and Graphene Nanoplatelets
J. Compos. Sci. 2019, 3(2), 38; https://doi.org/10.3390/jcs3020038
Received: 12 March 2019 / Revised: 2 April 2019 / Accepted: 3 April 2019 / Published: 8 April 2019
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Abstract
The effects of graphene nanoplatelets (GNPs) on the nucleation of the β-polymorph of polypropylene (PP) were studied when melt-mixed at loadings of 0.1–5 wt % using a laboratory scale twin-screw (conical) extruder and a twin-screw (parallel) extruder with L/D = 40. At low [...] Read more.
The effects of graphene nanoplatelets (GNPs) on the nucleation of the β-polymorph of polypropylene (PP) were studied when melt-mixed at loadings of 0.1–5 wt % using a laboratory scale twin-screw (conical) extruder and a twin-screw (parallel) extruder with L/D = 40. At low GNP loadings (i.e., ≤0.3 wt %), the mixing efficiency of the extruder used correlated with the β-nucleating activity of GNPs for PP. GNP agglomeration at low loadings (<0.5 wt %) resulted in an increase in the β-phase fraction (Kβ) of PP, as determined from X-ray diffraction measurements, up to 37% at 0.1 wt % GNPs for composites prepared using a laboratory scale twin-screw (conical) extruder. The level of GNP dispersion and distribution was better when the composites were prepared using a 16-mm twin-screw (parallel) extruder, giving a Kβ increase of 24% upon addition of 0.1 wt % GNPs to PP. For GNP loadings >0.5 wt %, the level of GNP dispersion in PP did not influence the growth of β-crystals, where Kβ reached a value of 24%, regardless of the type of extruder used. From differential scanning calorimetry (DSC) measurements, the addition of GNPs to PP increased the crystallization temperature (Tc) of PP by 14 °C and 10 °C for the laboratory scale extruder and 16-mm extruder, respectively, confirming the nucleation of PP by GNPs. The degree of crystallinity (Xc%) of PP increased slightly at low GNP additions (≤0.3 wt %), but then decreased with increasing GNP content. Full article
(This article belongs to the Special Issue Recent Advances in Graphene-based Nanocomposites)
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Open AccessArticle
Preparation of Piezo-Resistive Materials by Combination of PP, SEBS and Graphene
J. Compos. Sci. 2019, 3(2), 37; https://doi.org/10.3390/jcs3020037
Received: 30 January 2019 / Revised: 25 March 2019 / Accepted: 26 March 2019 / Published: 3 April 2019
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Abstract
The use of polyolefins in structural components requires the simultaneous improvement of stiffness and toughness of the matrix, whilst in the case of sensing components during operation, additional functions are needed such as electrical conductivity. However, providing various desired properties without impairing those [...] Read more.
The use of polyolefins in structural components requires the simultaneous improvement of stiffness and toughness of the matrix, whilst in the case of sensing components during operation, additional functions are needed such as electrical conductivity. However, providing various desired properties without impairing those intrinsic to the materials can be somewhat challenging. In this study we report the preparation of an isotactic polypropylene (iPP)/styrene–ethylene–butylene–styrene triblock copolymer (SEBS)/graphene system that combines enhanced mechanical properties with electrical conductivity. Blends were prepared by solution mixing (SoM) and solution/solid state mixing (SoM/SSM) formulation routes prior to melt processing. The nanocomposites were characterized by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) and the electrical and mechanical properties were evaluated. The materials prepared via the SoM/SSM route displayed good electrical conductivity while retaining the mechanical properties of iPP, making them attractive materials for low cost and high throughput structural components with sensing capacity. Full article
(This article belongs to the Special Issue Recent Advances in Graphene-based Nanocomposites)
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Open AccessArticle
Biocomposites Produced from Hardwood Particles by Equal Channel Angular Pressing Without Additives
J. Compos. Sci. 2019, 3(2), 36; https://doi.org/10.3390/jcs3020036
Received: 28 February 2019 / Revised: 27 March 2019 / Accepted: 30 March 2019 / Published: 3 April 2019
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Abstract
Equal channel angular pressing (ECAP) has been shown to be a promising method for producing biocomposites from wood particles. However, severe plastic deformation during ECAP would cause considerable cracking when consolidation is carried out without a binder. In this study, the processing conditions [...] Read more.
Equal channel angular pressing (ECAP) has been shown to be a promising method for producing biocomposites from wood particles. However, severe plastic deformation during ECAP would cause considerable cracking when consolidation is carried out without a binder. In this study, the processing conditions were investigated for ECAP of hardwood particles into bulk biocomposites without any additives. Crack formation and wood cell deformation were examined in conjunction with thermal stability and crystallinity of the biocomposites. In comparison with hot pressing without severe shearing, a decrease in crystallinity and severe deformation of wood cells occurred during ECAP. Improved processability and homogeneous deformation would occur at high ECAP temperature (e.g., 210 °C) or low ECAP speed (e.g., 10 mm/min), leading to reduced crack formation in the ECAP-produced biocomposites. Despite its tendency to cause periodic cracking, effective plastic deformation in the regions between cracks was shown to improve interparticle binding. Ongoing research points to the potential achievement of crack-free hardwood (HW) consolidated without a binder, leading to significantly enhanced strength. Full article
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Open AccessArticle
Composite Films of Waterborne Polyurethane and Few-Layer Graphene—Enhancing Barrier, Mechanical, and Electrical Properties
J. Compos. Sci. 2019, 3(2), 35; https://doi.org/10.3390/jcs3020035
Received: 9 March 2019 / Revised: 28 March 2019 / Accepted: 1 April 2019 / Published: 3 April 2019
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Abstract
Graphene has excellent mechanical, thermal, and electrical properties. Graphene can serve as potential reinforcement in polymer-based nanocomposites. In order to achieve this goal, graphene has to be distributed homogeneously and dispersed throughout the polymer matrix, establishing a strong interface with the polymer. Solution [...] Read more.
Graphene has excellent mechanical, thermal, and electrical properties. Graphene can serve as potential reinforcement in polymer-based nanocomposites. In order to achieve this goal, graphene has to be distributed homogeneously and dispersed throughout the polymer matrix, establishing a strong interface with the polymer. Solution mixing is an interesting method for the preparation of homogeneous nanocomposites, in particular when using environmentally friendly solvents such as water. The major difficulty met in the production of graphene/polymer composites concerns the preparation and stabilization of graphene in aqueous suspension. In the present work three different graphite-based materials, with different crystallinity and purity grades, were exfoliated in aqueous solution of an amphiphilic pyrene derivative, forming few-layer graphene (FLG). The FLG prepared was dispersed in waterborne polyurethane (WPU) to produce composite films. The composite films were produced by solvent casting and spray coating, forming free-standing films that were characterized in terms of its distribution of FLG through the composite, its permeability to water vapor, its electrical resistivity, and its mechanical properties. The studies demonstrated the influence of different factors on the composite film properties such as the use of graphite vs. FLG, the FLG lateral dimensions, and the FLG composition and composite preparation method. Full article
(This article belongs to the Special Issue Recent Advances in Graphene-based Nanocomposites)
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Open AccessArticle
Biological Activity and Nanostructuration of Fe3O4-Ag/High Density Polyethylene Nanocomposites
J. Compos. Sci. 2019, 3(2), 34; https://doi.org/10.3390/jcs3020034
Received: 14 March 2019 / Revised: 27 March 2019 / Accepted: 27 March 2019 / Published: 3 April 2019
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Abstract
We report here the synthesis of uniform nanospheres-like silver nanoparticles (Ag NPs, 5–10 nm) and the dumbbell-like Fe3O4-Ag hybrid nanoparticles (FeAg NPs, 8–16 nm) by the use of a seeding growth method in the presence of oleic acid (OA)/oleylamine [...] Read more.
We report here the synthesis of uniform nanospheres-like silver nanoparticles (Ag NPs, 5–10 nm) and the dumbbell-like Fe3O4-Ag hybrid nanoparticles (FeAg NPs, 8–16 nm) by the use of a seeding growth method in the presence of oleic acid (OA)/oleylamine (OLA) as surfactants. The antibacterial activity of pure nanoparticles and nanocomposites by monitoring the bacterial lag–log growth has been investigated. The electron transfer from Ag NPs to Fe3O4 NPs which enhances the biological of silver nanoparticles has been proven by nanoscale Raman spectroscopy. The lamellae structure in the spherulite of FeAg NPs/High Density Polyethylene (HDPE) nanocomposites seems to play the key role in the antibacterial activity of nanocomposites, which has been proven by nanoscale AFM-IR. An atomic force microscopy coupled with nanoscale infrared microscopy (AFM-IR) is used to highlight the distribution of nanoparticles on the surface of nanocomposite at the nanoscale. The presence of FeAg NPs in PE nanocomposites has a better antibacterial activity than that reinforced by Ag NPs due to the faster Ag+ release rate from the Fe3O4-Ag hybrid nanoparticles and the ionization of Ag NPs in hybrid nanostructure. Full article
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Open AccessArticle
Development of an Elastic Material Model for BCC Lattice Cell Structures Using Finite Element Analysis and Neural Networks Approaches
J. Compos. Sci. 2019, 3(2), 33; https://doi.org/10.3390/jcs3020033
Received: 27 February 2019 / Revised: 17 March 2019 / Accepted: 24 March 2019 / Published: 1 April 2019
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Abstract
Lattice cell structures (LCS) are being investigated for applications in sandwich composites. To obtain an optimized design, finite element analysis (FEA) -based computational approach can be used for detailed analyses of such structures, sometime at full scale. However, developing a large-scale model for [...] Read more.
Lattice cell structures (LCS) are being investigated for applications in sandwich composites. To obtain an optimized design, finite element analysis (FEA) -based computational approach can be used for detailed analyses of such structures, sometime at full scale. However, developing a large-scale model for a lattice-based structure is computationally expensive. If an equivalent solid FEA model can be developed using the equivalent solid mechanical properties of a lattice structure, the computational time will be greatly reduced. The main idea of this research is to develop a material model which is equivalent to the mechanical response of a lattice structure. In this study, the mechanical behavior of a body centered cubic (BCC) configuration under compression and within elastic limit is considered. First, the FEA approach and theoretical calculations are used on a single unit cell BCC for several cases (different strut diameters and cell sizes) to predict equivalent solid properties. The results are then used to develop a neural network (NN) model so that the equivalent solid properties of a BCC lattice of any configuration can be predicted. The input data of NN are bulk material properties and output data are equivalent solid mechanical properties. Two separate FEA models are then developed for samples under compression: one with 5 × 5 × 4 cell BCC and one completely solid with equivalent solid properties obtained from NN. In addition, 5 × 5 × 4 cell BCC LCS specimens are fabricated on a Fused Deposition Modeling uPrint SEplus 3D printer using Acrylonitrile Butadiene Styrene (ABS) and tested under compression. Experimental load-displacement behavior and the results obtained from both the FEA models are in good agreement within the elastic limit. Full article
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Open AccessArticle
Reactive Molecular Dynamics Study of the Thermal Decomposition of Phenolic Resins
J. Compos. Sci. 2019, 3(2), 32; https://doi.org/10.3390/jcs3020032
Received: 6 March 2019 / Revised: 21 March 2019 / Accepted: 23 March 2019 / Published: 28 March 2019
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Abstract
The thermal decomposition of polyphenolic resins was studied by reactive molecular dynamics (RMD) simulation at elevated temperatures. Atomistic models of the polyphenolic resins to be used in the RMD were constructed using an automatic method which calls routines from the software package Materials [...] Read more.
The thermal decomposition of polyphenolic resins was studied by reactive molecular dynamics (RMD) simulation at elevated temperatures. Atomistic models of the polyphenolic resins to be used in the RMD were constructed using an automatic method which calls routines from the software package Materials Studio. In order to validate the models, simulated densities and heat capacities were compared with experimental values. The most suitable combination of force field and thermostat for this system was the Forcite force field with the Nosé–Hoover thermostat, which gave values of heat capacity closest to those of the experimental values. Simulated densities approached a final density of 1.05–1.08 g/cm3 which compared favorably with the experimental values of 1.16–1.21 g/cm3 for phenol-formaldehyde resins. The RMD calculations were run using LAMMPS software at temperatures of 1250 K and 3000 K using the ReaxFF force field and employing an in-house routine for removal of products of condensation. The species produced during RMD correlated with those found experimentally for polyphenolic systems and rearrangements to form cyclopropane moieties were observed. At the end of the RMD simulations a glassy carbon char resulted. Full article
(This article belongs to the Special Issue Durability of Composites Under Severe Environmental Conditions)
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Open AccessArticle
Removal of Surfactant from Nanocomposites Films Based on Thermally Reduced Graphene Oxide and Natural Rubber
J. Compos. Sci. 2019, 3(2), 31; https://doi.org/10.3390/jcs3020031
Received: 28 February 2019 / Revised: 23 March 2019 / Accepted: 25 March 2019 / Published: 28 March 2019
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Abstract
Electrically conducting elastomer composites based on natural rubber and reduced graphene oxide (rGO) is reported. These composites were prepared by a latex method and an easy washing process. The latex method consists of the mixing of an aqueous suspension of rGO, stabilized by [...] Read more.
Electrically conducting elastomer composites based on natural rubber and reduced graphene oxide (rGO) is reported. These composites were prepared by a latex method and an easy washing process. The latex method consists of the mixing of an aqueous suspension of rGO, stabilized by sodium dodecyl sulfate and pre-vulcanized natural rubber, followed by solvent casting. The percolation threshold of composites was estimated at 1.54 wt.% of rGO. The washing process allowed elimination of the surfactant completely from nanocomposites. The absence of surfactant in nanocomposites was demonstrated by Raman spectroscopy and dynamo-mechanical analysis. The surfactant-free nanocomposites showed improved mechanical and electrical properties. Full article
(This article belongs to the Special Issue Sustainable Rubber Composites)
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