Journal of Composites Science — Open Access Journal

Polypropylene–cellulose composites have great potential in many important commercial applications, and it is important to understand and properly evaluate their biodegradative behavior to achieve improved composite formulations in accordance with their future applications. In the present study, an outdoor soil burial test was performed in order to evaluate the susceptibility to degradation of polyolefins–cellulose composites. The structural and morphological changes were analyzed by Fourier transform infra-red spectroscopy with attenuated total reflectance (FTIR-ATR) and scanning electron microscopy (SEM). The weight loss of composite samples after burying in soil was recorded. The presence of new bands, as an indicator of degradation, was confirmed by FTIR-ATR spectra. The thermal stability of the composites after soil burial analyzed by TGA was slightly improved, with relatively higher temperatures being required to decompose the samples after exposure to environmental factors. SEM micrographs presented some modifications of the polymer surface, such as holes, cracks, exfoliations, and fractures. Increasing the cellulose percentage of the composite samples led to increased weight loss. From the obtained results, it can be concluded that composites based on polyolefins and renewable resources undergo a slow process of biodegradation after contact with environmental microorganisms and, with appropriate composition, could be applied to various environmental fields. Full article

A nanocomposite based on reduced graphene oxide (rGO) and gold nanoparticles (AuNPs) was synthesized by the microwave-assisted hydrothermal method and applied in the determination of sulfamethazine (SMZ) in swine effluent using a glassy carbon (GC) electrode. The rGO-AuNPs nanocomposite was characterized morphologically, electrochemically and spectrochemically, showing that rGO was modified with the AuNPs. The GC/rGO-AuNPs electrode was optimized for the determination of SMZ, achieving detection limits of 0.1 μmol L⁻¹. The proposed sensor was successfully applied to the determination of SMZ in synthetic swine effluent samples. Full article

Hydrogel as a good water absorbent has attracted great research interest. A series of hydrogel based on polyethylene oxide (PEO) and acrylic acid (AAc) was prepared by applying gamma radiation with variation in the concentration of acrylic acid. Fourier transform infrared (FTIR) and scanning electron microscopy (SEM) were used to characterize the PEO/ AAc hydrogel. The properties of the prepared hydrogels such as gel content, swelling behavior, tensile strength, and pH sensitivity were evaluated. The formation of the hydrogels was confirmed from FTIR spectra. SEM images showed the inner porous structure of the hydrogels. The dose of gamma radiation was optimized to get a hydrogel with good swelling property and mechanical strength. The swelling ratio and gel content of the hydrogels were increased with increasing acrylic acid content. The pH of the solutions affected the swelling which indicated the pH-responsive property of the prepared hydrogels. Swelling of the prepared hydrogels in sodium chloride salt solutions decreased with increasing the ionic strength. Full article

Cellulose nanocrystals (CNCs) is a promising biodegradable nanomaterial with outstanding physical, chemical, and mechanical properties for many applications. Although aligned CNCs can self-assemble into bundles, their mechanical performance is reduced by interfacial strength between CNCs and a twisted structure. In this paper, we employ developed coarse-grained (CG) molecular dynamic (MD) simulations to investigate the influence of twist and interface energy on the tensile performance of CNC bundles. CNC bundles of different sizes (number of particles) are tested to also include the effect of size on mechanical performance. The effect of interfacial energy and twist on the mechanical performance shows that elastic modulus, strength, and toughness are more sensitive to twisted angle than interfacial energy. In addition, the effect of size on the bundle and twist on their mechanical performance revealed that both size and twist have a significant effect on the results and can reduce the strength and elastic modulus by 75% as a results of covalent bond dissociation. In addition, a comparison of the broken regions for different values of twist shows that by increasing the twist angle the crack propagates in multiple locations with a twisted shape. Full article

The automated fiber placement process (AFP) enables the manufacturing of large and geometrical complex fiber composite structures with high quality at low cycle times. Although the AFP process is highly accurate and reproducible, manufacturing induced imperfections in the produced composite structure occur. This review summarizes and classifies typical AFP-related manufacturing defects. Several methodologies for evaluating the effects of such manufacturing defects from the literature are reviewed. This review paper presents recent scientific contributions and discusses proposed experimental and simulation-based methodologies. Among the identified ten defect classes, gaps and overlaps are predominant. This paper focuses then on methods for modelling and assessing gaps and overlaps. The state of the art in modelling gaps and overlaps and assessing their influence on mechanical properties is presented. Finally, research gaps and remaining issues are identified. Full article

The main objective of the present study was to develop a fire thermal model able to predict the evolution of the temperature and decomposition gradient across a laminated composite structure when exposed to fire. The thermal response of composite laminate made of organic polymer matrix was investigated under severe temperature conditions as samples were exposed to high temperatures up to 750 °C. The highlight is that a behavior law for water is included in our thermo-mechanical model to estimate effects due to a moisture content field on the thermal response of composite laminates. In particular, porosity and gas pressure are strongly influenced by the presence of water in the material and modify the thermal behavior accordingly. This enabled us to propose a new approach that can be used for the prediction of hygro-thermo-chemico-mechanical post-combustion properties in a very large number of material and fire scenarios. Full article

This work aimed to characterize the deportment/concentration and liberation/association of the metals and light elements within mechanically processed waste printed circuit boards (PCBs) that hold the complex and heterogeneous structure and distribution of different material components. Waste PCBs passed through a series of mechanical processing (i.e., comminution and sieving) for metal recovery and were then characterized without further destroying the particles in order to capture their heterogeneity. The characterizations were performed in a laboratory and large-scale neutron facility. The results obtained with a portable X-ray fluorescence spectroscopy and prompt gamma activation analysis were compared and confirmed the good agreement and complementarities in general. The advantages and disadvantages of the two different methods were identified and discussed in this paper, in relation to their application to the analysis of mechanically processed PCB particles. Full article

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

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 T_onset by almost 40 °C. The DSC results showed that severe matrix degradation and the presence of bioglass did not significantly affect glass transition temperature (T_g), melting temperature (T_m) and crystallinity of PLAs, but it influenced cold crystallization peak (T_cc). 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

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

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

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

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

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

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

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

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

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

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