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Flammability of wood composites has always been of a concern. To investigate whether CaCO3 particles are efficient fire-retardant fillers for wood composites, wood composites were prepared with Phenol Formaldehyde (PF) resin and pine flakes that were deposited with CaCO3 by the treatments of Na2CO3 and CaCl2. The flammable performance, Limiting Oxygen Index (LOI), simultaneous Thermogravimetric Analysis and Differential Scanning Calorimetry (TGA–DSC), mechanical properties, and water resistance of wood-flake composites deposited with CaCO3 were evaluated. Furthermore, the Scanning Electron Microscopy (SEM) was used to observe the surface morphology of the treated wood flakes, showing that CaCO3 microparticle crystals grew onto the wood flake surfaces. The increase of reactant concentrations from 0.5 M to 1.0 M resulted in an increase in LOI and improvements of the flame-retardant performance of the composites. The TGA–DTG examination showed that the decomposition peak of the treated wood flakes shifted to a lower temperature range. The TGA also demonstrated that the treatment contributed to the accumulation of char layer, which benefited the flame retardancy of the composites. The growth of energy consumed during the sample pyrolysis could be attributed to the insulation of CaCO3 and thicker char layers. After the treatment with reactants (concentration of 0.5 M), although the internal bonding (IB) slightly decreased by 8.3%, the modulus of elasticity (MOE) and the modulus of rupture (MOR) of the composites significantly increased by 182.9% and 63.5%, respectively.

The gradual replacement of conventional materials by composite materials becomes reality when specific properties cannot be achieved by the former. Also, the search for new composites that use natural fibers or a mixture of natural fibers with synthetic fibers as reinforcement is being carried out. Thus, a research was made on the development of two composite laminates, one based on piassava fiber fabric and the other a hybrid composite based on piassava fiber and glass-E fabrics, in order to compare the mechanical behavior of both. The laminate plates were prepared and were processed for specimen manufacture in accordance with the specifications of ASTM D3039 - Uniaxial Tensile Test, and ASTM D790 - Three-point Bending Test standards. Scanning Electron Microscopy (SEM) was also performed to analyze the mechanisms of damage of the specimens. The analysis of the results of the tested specimens show they are satisfactory, as they are very akin to the results of other materials already researched by academy.

An interface model of homogenization was proposed, this model considers the influence of the inclusions size of the micrometre range on the elastic properties of composites. The appearance of surface strains and shear stresses at the interphase boundary is associated with the "sticking" of the matrix to the surface of the inclusions. The effective modulus of elasticity of a composite is the sum of two terms: a constant part in the form of a modulus of elasticity of a bulk material, and a variable part that is caused by a shift at the interphase boundary and depends on the particles size. Absolute of particles sizes were considered by introducing within the interfacial model empirical elasticity modulus of the composite with the one basic particle size. The results of the calculation are in good agreement with the experimental data for Young's modulus of polymer composites with spherical particles.

The carbon fiber based composites: carbon fiber reinforced plastic and 3D carbon fiber reinforced carbon composites were exposed to the Nd3+: YAG laser beams (1064 nm). Experimental parameters for the interaction of the laser beam with 1.5 Hz pulse frequency and with pulse duration 0.7 ms varied: energy density between 128 and 1915 J cm(-2), pulse energy from 1 to 3 J and mean power in the range between 0.4 and 6.5 kW. Apparently, the energy absorbed by the composite samples was mainly converted into thermal energy, causing a range of damages, from instantaneous evaporation to cracking and melting, which resulted in a crater-like damage. Program ImageJ was executed for quantitative analysis of generated damages based on micrographs obtained by SEM and light microscopes. Obtaied results enable identification of the laser induced changes in the material. (C) 2017 Elsevier Ltd. All rights reserved.

In the current research a statistical micromechanical approach for the determination of the mechanical properties of composite materials is proposed. The proposed method is mainly based on the well-known periodic homogenization scheme. The methodology implements multi-step multiscale approach to calculate the mechanical properties of composite materials where the statistical characteristics (e.g. size, aspect ratio, orientation) of the reinforcing phase are known as probability distribution functions (PDF). The calculations start from Unit Cell I which resembles the microstructure of material at the lowest length scale and continue until the largest fiber is considered in the final unit cell setting. The results of the presented theory are compared with experimental data on composite materials which show that good estimates of the elastic moduli can be achieved by using statistical multi step homogenization technique.

In this work, volcanic basalt rocks, which were collected from different parts of Van city located in Eastern Anatolia, have been discussed in the context of impedance properties. The real and imaginary components of dielectric constants, dielectric dissipation factor, dielectric strength, AC conductivity and s frequency exponent parameter have been determined. According to AC conductivity results, it has been determined referring to s parameters' values, correlated barrier hopping (CBH) model is valid for all volcanic basalt rock samples at high frequency region. Moreover, the critical frequency that corresponds to the change of conductivity characteristic of all basalt volcanic rocks has been determined. Furthermore, due to their low conductivities Sample-1 and Sample-2 have been suggested as promising materials for electromagnetic radiation shielding applications for the high and low frequency regions, respectively.

Improving the utilization of industrial thermal waste and abundant solar thermal energy is of immense significance in energy management and thermal engineering. Latent heat thermal storage is one of the emerging methods that employ the large caloric density of materials mainly as a result of its constant-temperature phase-change process. Herein, paraffin was selected as the phase-change matrix which was reinforced with length controlled-carbon nanotubes (LCCNTs) as the primary filler and graphene nanoplatelets (GNPs) as the secondary reinforcing nanoparticles. Electrical conductivity (EC) of samples was tested, and carbon nanotube (CNT) was proved to be more effective in the increase of EC, than GNP. Furthermore, the thermal conductivity of the fabricated composite phase-change material was measured, and at the filler ratio of 5 phr an enhancement of about 148.0% was found compared with that of pristine paraffin. Optimal CNT/GNP ratios were also determined at the maximum enhancement achieved for each property. To observe the effect of LCCNTs on the mechanical properties of composites, polyester resin-based composites were prepared, and the tensile strength results are reported.

This paper describes the changes in some structural, mechanical and tribological properties of an MMC based on sintered Cu–Sn bronze reinforced by an alumina additive. If a correct percentage of the additive is added, the values of the MMC bending strength and strength limit in compression do not change, but a reduction of the friction coefficient and the wear rate is observed in the case of both the concentrated and distributed contact of the MMC with C45 steel is observed. SEM analysis indicates events of abrasive and adhesive wear of friction surfaces of the MMC and C45 steel and also mass transfer.

A composite’s microstructure significantly influences its overall properties. Orientation and aspect ratio of the fiber are two key parameters that describe the microstructures of a composite with straight short fibers. This paper discusses the effects of fiber orientation and aspect ratio distribution on the overall elastic properties of composites using the Mori–Tanaka’s method in this paper. The results show that using an average aspect ratio of the fibers to estimate overall elastic properties is not appropriate under some conditions. When the aspect ratio of the fibers does not follow a symmetric distribution, the overall elastic properties obtained by the average aspect ratio of the fibers may differ by more than 30% from those obtained by the method considering the aspect ratio distribution. This paper presents a model used to predict the properties of nanotube-reinforced composites. The results obtained by the model were compared with experimental results.

The interphase properties greatly affect the compressive strength of thick composite materials. To characterize the interphase properties, a SIEM (Speckle Interferometry with Electron Microscopy) technique is established. Its capability is demonstrated by an application for determining the effective Young's modulus of the interphase of a metal matrix composite SCS-6/Ti-6-4.

The aim of this research is the production of epoxy resin composites reinforced by birch, palm, and eucalyptus fibers with resin transfer molding technique and molded fiber production technique combination. The tensile stress of birch, palm, and eucalyptus reinforced epoxy composites were determined as 29.53, 42.24, and 45.28 MPa, respectively. Bending stress of birch, palm and eucalyptus reinforced epoxy composites were found as 58.83, 68.58, and 79.92 MPa, respectively. The birch epoxy composite had 0.105 J impact energy while palm and eucalyptus epoxy composites were determined as 0.130 and 0.124 J, respectively. It is clearly observed that fiber type was very effective on the mechanical properties of composites. The results of studies showed that molded fiber production method had a very promising future for the development of natural fiber reinforced composites. © 2019 Elsevier Ltd

The carbon-fiber-reinforced composites modified by nano-silica were successfully prepared using RFI technology. And the properties of composites also were studied. The investigations revealed that the properties of composites were increased by filling nano-silica. With the increase of nano-silica content, the density of carbon-fiber-reinforced composites was increased, while the glass transition temperature, tensile strength and flexural strength were first increased and then decreased. At the nano-silica content of 3 wt%, the glass transition temperature reached a maximum of 117.3 °C. When the nano-silica content was 4 wt%, the tensile strength and flexural strength were increased to 595.69 and 703.76 MPa, which were improved by 86.30% and 126.98% compared with the composites without nano-silica. Therefore, the best properties of carbon-fiber-reinforced composites was obtained with filling 4 wt% nano-silica content, while the toughening and strengthening effect was optimal, since nano-silica as a reinforced material were filled the gap between epoxy resin and carbon fiber to disperse the external force.

By designing the fiber/matrix interface, the properties of the carbon fiber-reinforced composite can be changed significantly. In this work, carboxylic-functionalized carbon nanotubes (CNTs) and graphene oxide (GO) were separately deposited on the carbon fiber (CF) surface to increase the interfacial properties of composites. The properties of fibers such as the surface topography, surface chemical composition and surface energy were examined, and the interfacial shear strength between the fibers and the matrix was examined using a microdroplet test. In addition, CNT-coated, GO-coated and pristine unidirectional carbon fiber fabrics were used to manufacture CF/epoxy composites via the vacuum-assisted resin transfer molding method, and their moisture absorption and interlaminar shear strength were measured. The results reveal that both CNTs and GO can significantly improve the interfacial properties of composites. The CNT/CF-reinforced composites have higher shear strength, and the GO/CF-reinforced composites have better humidity resistance. The interfacial reinforcing mechanisms of the composites with CNTs and GO were compared.

In this study, thermal aging process was applied to glass fiber (GF) and carbon fiber (CF) reinforced poly(ether ether ketone) PEEK composites and effects of this process and reinforcement type on thermal, thermomechanical, tribological, physical and morphological properties of PEEK composites were evaluated. All the results demonstrated that a transcrystalline layer was formed between the fiber and matrix in the composites under applied thermal aging condition and this layer affected the fiber–matrix adhesion, reduced the energy dissipation in this region and improved the properties of composites. As a result of this study, it was proved that the thermal aging process is an efficient method to control the thermal, thermomechanical, tribological and physical properties of composites and these properties of composites can be improved by using this method.

Polymeric composites have the potential to replace current electronic packaging and improve thermal management of electronics to open the way for further size shrinkage. Such composites need to provide high thermal conductivity and high electrical resistivity while possessing suitable mechanical properties. This paper reports the study of thermal behavior of arranged and random network of hexagonal boron nitride (hBN) in composite with different polymers. Thermal barrier factors and possible solutions to reduce the effect of these factors are thoroughly investigated. Thermal behavior of hBN filler network in composite with different polymers as well as the possibility of using green (bio-based) polymers as the matrix have been studied. Fully bio-based, partially bio-based and petroleum based composites are compared to investigate the effect of different polymer matrices on thermal properties of composites. Designed high thermally conductive and electrically insulative composites are expected to possess unique properties. This includes being lightweight, injection moldable, low coefficients of thermal expansion, eco-friendly, and with proper service temperature and mechanical properties. Such composites will result in more compact, lighter and cheaper electronics with higher performance, by avoiding the use of electrical fans, heat sinks and other methods of heat dissipation.

Continuous natural fibre reinforced thermoplastic composite materials not only offer low weight and better strength than short fibre reinforced composites but are also biodegradable and eco-friendly. The impregnation of resin into the reinforcement is considered as a major concern during the fabrication of thermoplastic composites. Therefore, intermediate materials known as comingled fabrics were developed to assist the fabrication of continuous fibre reinforced thermoplastic composites by aligning the polypropylene fibres alongside the reinforcement natural fibres (jute, hemp and flax) using weaving and knitting techniques. Cross-ply composite panels were fabricated using hot press compression moulding method. The novelty of this work is the simplified methodology to develop the comingled fabrics and the effects of comingling on the mechanical properties of composites. The effect of the comingling technique on the tensile, flexural and impact properties of composites is explained in this research work. Knitted comingled composite specimens exhibit superior mechanical properties than woven comingled composite specimens. The experimental results have shown 14%, 7% and 3% increase in tensile strength, 25%, 20% and 13% increase in flexural strength and 37%, 54% and 44% increase in impact strength of knitted comingled specimens of jute, hemp and flax respectively.

In the present study artificial neural network (ANN) approach was used for the prediction of effect of physical and mechanical properties of Al2024–B 4 C composites produced by powder metallurgy. Effects of reinforcement size and content (wt.%) on the physical and mechanical properties of composites were determined by measuring the density, hardness and tensile strength values. Density, hardness and tensile values strength of the composites were the outputs obtained from the proposed ANN. It was found that the effect of reinforcement size and content on the homogeneous distribution of B 4 C particles is as important as the effect of milling time. By comparing the predicted values with the experimental data, it was demonstrated that the well-trained feed forward back propagation ANN model is a powerful tool for prediction of effect of physical and mechanical properties of composites.

This paper reports the results of an experimental investigation on the thermophysical properties of composites materials (Epoxy resin/paraffin spheres) and (Epoxy resin/metal tubes) filled with paraffin developed to improve different properties of PCM and open a wide field of applications to latent heat storage systems. The objective of this research is to use PCM composite as integrated components in a passive solar wall. The proposed composite TROMBE wall allows daily storage of the solar energy in a building envelope and restitution in the evening, with a possible control of the air flux in a ventilated air layer. An experimental set-up was built to determine the thermal response of these composites to thermal solicitations. The results have shown that most important thermal properties of these composites at the solid and liquid states, like the “apparent” thermal conductivity, the heat storage capacity and the latent heat of fusion. Experimental investigations of the thermophysical properties of composites materials (Epoxy resin/metal tubes) filled with paraffin have shown that these materials combines a high heat storage capability and an enhanced heat transfer at the same time.

The addition of carbon nanotubes (CNTs) in natural fibre based hybrid composites as filler to enhanced low velocity impact (LVI) and compression after impact (CAI) properties of composites are not explored by researchers in literature. In this study, we examined the effect of using multi-walled carbon nanotube material (MWCNT) as nanofillers in LVI followed by ultrasonic wave propagation imaging (UWPI) to visualize the impacted damage and CAI properties of bamboo/glass fibre hybrid composites. Hybrid composites containing 0.5% weight fractions of CNTs were compared with the control hybrid composites. The experimental results revealed that adding CNTs into the hybrid composites show less energy absorption, improved peak force, and increased deflection at maximums of 9.21%, 36.23% and 26.06% respectively in terms of LVI properties. Furthermore, smaller damage size was detected by non-destructive approach for CNTs/hybrid composites as compared to the controls. A maximum of 23.67% increment on CAI strength obtained by addition of CNTs into hybrid composites. We concluded that addition of CNTs into bamboo/glass hybrid composites improved impact and after-impact properties.

In order to simultaneously improve the dispersibility of graphene in the bismaleimide (BMI) resin and the interfacial interaction between them, the polytriazine@RGO nanocomposite (PTZ@RGO) with terminal amine was obtained by the method of one-step precipitation polymerization. The PTZ@RGO hybrid nanocomposite was then chosen as filler to improve the mechanical and tribological properties of BMI resin. Through effective surface modification, the compatibility and interface strength between graphene and BMI matrix were significantly improved, leading to the flexural strength, impact strength, anti-friction, wear resistance and thermal stability of PTZ@RGO/BMI composites were significantly improved as compared to those of neat BMI resin and RGO/BMI composites. The other properties including hardness and thermal properties of composites were all improved with increasing amount of PTZ@RGO fillers. These high performance BMI composites have a great potential for application in aerospace, mechanical engineering and other automobile brake devices.

This study investigated the flexural properties and failure behavior of CF/PA6 plain woven laminates with different layers (i.e., 2, 4, 10 and 16 plies) fabricated by the hot compression technique. Step-by-step interrupted three-point flexural tests and optical observation were performed to study the failure mechanisms of CF/PA6 plain woven laminates with different layers. Incremental cyclic flexural loading tests were carried out to investigate cyclic cumulative damage. The results indicate that the flexural strength of various CF/PA6 plain woven laminates follows the Weibull distribution and that 16-layer laminates show a higher Weibull modulus than the other types of laminates. The flexural initial fracture point (matrix cracking), flexural knee point (intralaminar cracking) have also been identified based on the observation of about 50 specimens for each type. The knee point plays a critical role in determining the flexural properties of composites whereas initial fracture is not a critical factor for the flexural properties. The typical three stages (i.e., initial stage, smooth stage and damage stage) of a fatigue degradation process of various CF/PA6 plain woven laminates during incremental cyclic loading flexural tests were observed. The flexural knee point stress is near the abrupt stiffness degradation limit stress in the present study.

The dimensional stability and dynamic mechanical properties on bamboo (non woven mat)/kenaf (woven mat) hybrid composites was carried out in this study. The hybridization effect of bamboo (B) and kenaf (K) fibers at different weight ratio were studied at B:K:70:30, and B:K:30:70 while maintaining total fiber loading of 40% by weight. The coefficient of thermal expansion (CTE) and dynamic mechanical properties of composites were analyzed by thermomechanical anlayzer (TMA), and dynamic mechanical analyzer (DMA), respectively. Positive hybridization effects were observed on B:K:50:50 hybrid composite with lowest CTE and highest dynamic mechanical properties among all composites. The dimensional stability were strongly influence by the fiber orientation where all composites shows prominent expansion in the transverse fibers direction but relatively low expansion in longitudinal fibers direction. Dynamic mechanical properties in term of complex modulus (E*), storage modulus (E′), loss modulus (E″), Tan delta and Cole-Cole plot were studied. DMA results reveal that B:K:50:50 hybrid composite possess the highest complex modulus due to the strong fiber/matrix interfacial bonding which supported by the coefficient of effectiveness and Cole-Cole plot. Hence, it is concluded that 50:50 weight ratio of bamboo and kenaf fibers is the optimum mixing ratio to enhance both dimensional and dynamic mechanical properties of hybrid composites, and it can be utilized for automotive or building materials applications which demand high dimensional stability and dynamic mechanical properties.

Because of increased usage areas, and advances in characterization of the nanostructured materials, determination of the engineering properties of composites that includes carbon nanotubes has gained importance. It is possible to designate material properties of carbon nanotube based composites theoretically and experimentally. In this study, engineering constants of carbon nanotube based unidirectional carbon fiber reinforced composite lamina determined theoretically with two different approaches. Then, a composite plate whose laminas were stacked up as a [0°/+45°/-45°/90°]s layup was built up in ANSYS, ACP Module. Finally, three point bending analyzes were performed separately under concentrated and distributed load. The results showed that there were negligible differences between the engineering constants obtained from two different theoretical approaches. Engineering constants, E1, E2, G12 and G23, increased as the added carbon nanotube fraction is increased. Besides that, flexural rigidity of composite plate also showed ever-decreasingly increase, as carbon nanotube content is increased. The results of theoretical and numerical bending analyzes exhibited a good agreement with the maximum percentage relative error of 9.1.

Acrylonitrile butadiene styrene (ABS) nanocomposites with multiwalled carbon nanotubes (MWCNTs), reduced graphene oxide (RGO) and graphene oxide-carbon nanotubes (GCNTs) reinforced acrylonitrile butadiene styrene (ABS) composites were prepared using twin screw extruder. The effect of these reinforcements on dynamic rheological properties of composites was studied. Different carbon nanofillers significantly enhanced the viscoelastic properties of nanocomposites. The rheological studies showed that the material undergoes viscous to elastic transition for 5 wt % MWCNTs, 10% RGO and 7% GCNTs reinforced in ABS matrix. GCNTs hybrid composites show a higher dispersion as well as effectiveness for increased filler amount as compared to RGO and MWCNTs based ABS composites. The dynamic intersection frequency of GCNTs-ABS composites indicates its superiority over MWCNTs and RGO based ABS composites by solving the problem of restacking of graphene and agglomeration of MWCNTs. Modified Carreau-Yasuda model and Hershcel-Bulkey model have been used to determine the yield stress of the composites and van Gurp-Palmen plot to determine the viscoelastic properties. These models were used to compare the theoretical results with experiment data. Dynamic rheological measurements revealed the viscous-like (G">G') behavior at the lower loading of filler and elastic like (G'>G") behavior at higher loading of carbon nanofiller.

Environment friendly conductive polymer composites (CPCs) with high electromagnetic interference (EMI) shielding performance and favourable mechanical properties were successfully produced on large scale from poly ( l -lactid acid) (PLLA), poly (lactic acid) stereocomplex crystallite (PLASC) and multi-wall carbon nanotube (MWCNT). The morphology results indicated that the perfect segregated structure was easily manipulated by controlling the injection temperature. The prepared composite exhibits good conductivity and high EMI shielding effectiveness (EMI SE) under low MWCNT content due to the selective dispersion of the conductive MWCNT in the continuous PLLA phase. With the addition of only 3 wt% MWCNT, the composite exhibits high electrical conductivity of 6.42 S/m and outstanding EMI shielding performance of 31.02 dB at 8.2 GHz. Moreover, similar molecular structure between PLLA and PLAsc endowed excellent interfacial adhesion, thus results in favourable mechanical properties of composites. The work provides a novel idea for manufacting high EMI shielding materials with both toughness and degradation.

The fire performance of fiber-reinforced polymer composites used in naval ships, submarine and maritime structures are reviewed and discussed in this work. Polymer composites has been developed and used for wide range of applications in aircraft, spacecraft, boats, ships, automobiles, civil infrastructure, sporting goods and consumer products grown at an impressive rate over the last 50 years. In particular, the use of composites for naval vessels continues to grow in coming years for various applications including decks, bulkheads, propellers, propulsion shafts, pipes, pumps, and other machinery parts. Composites demonstrated as ideal materials in a wide variety of applications due to many outstanding physical, thermal-mechanical and chemical properties. Specifically, composites offers high specific stiffness and specific strength, low density, good fatigue resistance, outstanding corrosion resistance, excellent thermal insulation and low thermal expansion over many metal alloys. A major disadvantage of many composite materials is poor performance when exposed to high temperatures, in which the organic matrix decomposes with the potential to release of heat, smoke, soot and toxic volatiles. Offshore environment poses even more challenges for naval structure design, where fires although infrequent can have catastrophic effects due to their intensity and the isolation of the offshore construction. Although most of polymer composites are flammable, their resistance to pyrolysis can be improved.

Lightweight porous materials for electromagnetic interference (EMI) shielding applications are reviewed. EMI shielding refers to the capability of a material to protect from electromagnetic fields (EMFs) generated by electronic devices. Traditionally conducting metals are used in EMI shielding applications, which are slowly being replaced by conducting polymer based shields. This review is narrowly focused on understanding the approaches related to porous high EMI shielding composite materials that have very low density values. While metallic fillers can increase the EMI shielding capabilities of polymers, they also increase the weight, which can be offset by inducing the porosity in the matrix. Porosity is found to be effective in providing higher shielding effectiveness at low filler volume fraction due to concentrating the filler in the solid polymers. However, use of gas porosity results in composites with low mechanical properties. This problem can be alleviated to some extent by reinforcing polymer foams with lightweight conductivefillers such as carbon nanofibers (CNFs), carbon nanotubes (CNTs) and graphene. But the properties of pores such aspore size and distribution cannot be effectively controlled in such cases. Syntactic foams containing hollow particle fillers seem to be the best combination of EMI shielding capabilities and mechanical properties. These composites can be either filled with a second phase conducting filler, or hollow particles can be coated with a conducting layer, or hollow particles made of conducting materials can be used as fillers. The hollow particle wall thickness and volume fractions can be optimized to obtain the desired combination of properties in syntactic foams to enable their multifunctional applications.

Poly (lactic acid) (PLA) reinforced with bleached kraft soft wood (BKSW) biocomposites with fibre content up to 35% were processed by kinetic mixing and injection moulding. The cellulosic filler was a commercial chemical bleached kraft soft wood pulps composed of well individualized fibres free from lignin with diameter about 20 μm and length within micron scale. The effect of fibre addition on the thermal properties of composites was investigated using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermal gravimetric analysis (TGA) and thermo-mechanical analysis (TMA). In a previous work, it was demonstrated that fibre inclusion on PLA enhanced the modulus as well as the strength. Fibre addition promoted the crystallization of PLA by favouring the heterogeneous nucleation and accelerating the crystallization kinetic, without adversely altering the thermal stability. The DMA analysis confirmed the strong stiffening effect brought by the addition of fibres at the glassy as well as the rubbery domains. The presence of fibres had also a beneficial effect on the dimension stability by lowering the thermal expansion coefficient of composites.

Poly(ethylene terephthalate) (PET) composites were loaded with four different carbon-based fillers: functionalized carbon nanotubes (CNT), exfoliated graphite (EG), and hybrid materials such as Mg(OH)2, which is primarily used as a flame retardant additive in plastics, dispersed over functionalized CNT and EG. The technology used to mix the different phases was high energy ball milling in dry conditions and at ambient temperature. Morphological organization, thermal and electrical properties of composites were evaluated and correlated with the type of filler. The electrical properties were analyzed over a wide temperature range, from 25 °C to 150 °C, and correlated to the starting structural organization of the composites and the morphological transformations occurred during the thermal heating. The addition of EG and CNTs to PET did not have influence on the amorphous arrangement of unfilled PET, while the loading of Mg(OH)2/EG and Mg(OH)2/CNT fillers favoured the PET crystallization. The crystallization inducted by temperature allowed an increasing in electrical conductivity of the starting amorphous samples. On the other hand, it was found a conductivity independent of temperature for semicrystalline samples (filled with Mg(OH)2/EG and Mg(OH)2/CNT). The charge transport, for the analyzed PET composites, is favoured by the higher degree of crystallinity.

A hybrid model of nonlinear homogenisation of anisotropic composites was developed, based on the secant Eshelby's model of the second order. At first a scaling factor was determined between constrained strains of matrices of finite and infinite dimensions for an isotropic composite. The scaling factor was then used to calculate the constrained strain of the matrix and the macrostress of the anisotropic composite. If the calculation results and reference values differ greatly, the scaling factor serves as a fitting parameter. A parametric hybrid model has been developed to predict the properties of composites with different content of inclusions. Good agreement of the calculation results with the numerical solutions of the FEM and experimental data was obtained.

In this study, ethylene propylene diene monomer (EPDM)/barium titanate (BaTiO3)/mica (or graphite) composites with different volume fraction of mica (or graphite) were prepared by two-roll milling process. Thermal conductivity, crosslink density, cure, rheological, mechanical and dielectrical properties of composites were investigated. The results of rheological properties indicated that the 15 vol% mica made the complex viscosity of EPDM/BaTiO3 compound to become non-sensitive to varying shear. In terms of mechanical properties, only 5 vol% graphite flakes remarkably improved the tensile strength of EPDM/BaTiO3 (70/30) from 7.47 MPa to 13.20 MPa (76% increase). By comparison, the 20 vol% mica just increased the tensile strength of EPDM/BaTiO3 (70/30) to 12.10 MPa. In addition, 20 vol% graphite flakes boosted the thermal conductivity and dielectric constant of EPDM/BaTiO3 (70/30) from 0.323 W m−1 K−1 and 7.1 at 40 MHz to 2.421 W m−1 K−1 (749% increase) and 70 at 40 MHz (almost 1000% increase), respectively. The excellent electric and thermal performance was attributed to the mobile π electrons in graphite flakes.

In this study, bamboo fiber filled polypropylene composites (BPCs) were prepared using bamboo and coconut shell charcoal as reinforcing fillers for enhancing the properties of composites. Bamboo and coconut shell biomass were carbonized at different carbonization temperatures (300, 400, 600, and 900OC); 1 h soaking time and at 5OC−min heating rates. The effect of carbonization temperature and charcoal content (0.5%, 1.0% and 1.5%) on mechanical, thermal and water absorption properties of BPCs has been investigated. The experimental results show that charcoal which is obtained at lower pyrolysis temperature (300OC and 400OC) improves the strength properties of BPCs, whereas, strength properties remains unaltered when charcoal prepared at elevated temperatures (600OC and 900OC) are added to BPCs. Compared to coconut shell charcoal (CSC) better mechanical properties were obtained through bamboo charcoal (BC). This has been attributed to flakes like appearance of BC, having pores present on their surfaces. The study also shows that addition of charcoal provides thermal stability to BPCs, particularly via charcoal prepared at elevated temperature (900OC). The optimum temperature for achieving sufficient hydrophobicity in BPCs is found to be 300OC and 600OC for BC and CSC, respectively.

With an objective to make automotive parts environmentally friendly by replacing glass fibers with natural fibers for underbody shield application, this paper investigates the water absorption behavior of three types of compression-molded composites: all-glass (25% by wt.), all-kenaf (25% by wt.) and hybrid (12.5% glass and 12.5% kenaf by wt.) with polyethylene terephthalate matrix and Acrodur® binding agent at ambient (23 °C) and elevated (70 °C) temperatures. Specimens saturated at ambient temperature were then subjected to various hygrothermal conditionings: freeze-thaw cycling between 23 °C and −29 °C; extended freeze at −29 °C; and re-drying. Standard flexural tests showed the degradation in mechanical properties was a strong function of water absorption. At dry conditions, both flexural modulus and strength for hybrid and all-kenaf composite were much higher compared to all-glass composite. After saturation, the mechanical properties of all-kenaf and hybrid composite, despite being significantly affected by water absorption, were comparable to the saturated all-glass composites. As expected, the mechanical properties of composites saturated at 70 °C were severely affected where the modulus decreased by about 55% for the hybrid and all-kenaf composites. However, freeze-thaw cycling and extended freeze did not have any significant impact on the mechanical properties of the saturated composites. Interestingly, the flexural strength for all composites increased after the saturated specimens were re-dried. This phenomenon was attributed to the added crosslinking in the Acrodur matrix. Also, sound absorption tests and muffler tests showed that glass fibers can be replaced by kenaf fibers without compromising the performance.

This work aims to improve heat resistance and mechanical properties of PEEK composites by filling the modified phosphates with inorganic particles (Si3N4, AlN, Al2O3 and Cu2O) as reinforcements. The modified phosphate/PEEK composites were successfully prepared by pre-mixing and compression molding. The crystalline structures and compositions of modified phosphates and composites are characterized. Furthermore, the thermal and mechanical properties of composites were evaluated by thermal aging resistance at 350 °C for 24 h. The results show that all the four kinds of phosphate reinforcements can enhance the thermal aging resistance of phosphate/PEEK composites to varied extent. For the modified phosphate by Al2O3, its addition increases the 30% weight loss temperature (T30) by 55 °C. Moreover, the compressive strength exhibits a 105.6% enhancement, reaching 321.4 MPa from 156.3 MPa of the PEEK matrix. This work provides a valuable route to improve the thermal and mechanical properties of PEEK composites, which would have promise applications in heat-resistant and high-strength structural materials.

In this study, the mechanical properties and crack densities of two kinds of hydroxyl-terminated polyurethane (HTPU1 and HTPU2) toughening epoxy/carbon fiber composites were investigated in detail by hot-press molding process. The results showed the toughening epoxy (EP) could effectively improve the mechanical strengths of composites at room temperature (RT) and cryogenic temperature (77 K) due to the improvement of interfacial adhesion between the matrix and fibers. EP/HTPU1 showed the best tensile properties of the EP matrix, but CF/EP/HTPU2 showed the highest longitudinal tensile strength, due to the existence of granular rubber precipitates after curing, which has the capability of cavitation leading to more balanced failure. Different tensile properties of matrix and composites showed the tensile properties of composites were strongly affected by the microstructure after curing and interfacial adhesion between matrix and fibers. Optical microscopy image analysis suggested that the presence of HTPU can prevent the formation of micro-cracks during thermal cycles at cryogenic condition of composite laminates.

The construction of heat conduction paths in the polymer matrix is essential to improve the thermal management performance of polymer composites. A three-dimensional (3D) thermally conductive network with regular filler structures is very attractive for building fast conductive paths in polymer composites. Herein, a unique 3D interconnected tannic acid modified boron nitride (BN) and C network (M-BN/C) was successfully fabricated by the carbonization of M-BN/thermoplastic polyurethane (TPU) skeletons, which were obtained via simple salt template assisted strategy to enhance the thermal transfer properties of composites. The highly thermally conductive epoxy composites (M-BN/C/EP) were then prepared by impregnating epoxy resin (EP) into the 3D M-BN/C network. The thermal conductivity of the composites with a M − BN loading of 23 wt% is as high as 1.524 W/(m·K), which exhibits a significant enhancement of 702% compared with pure EP. In addition, our composite exhibited outstanding thermal behaviors during heating and cooling processes. Furthermore, the finite element heat conduction simulation further analyzes the heat conduction mechanism of epoxy composites from the theoretical level. This work provides a new idea to significantly enhance the thermal conductivity of thermal management materials.

A new type of polymer composite was synthesized from peat ash which was obtained as industrial waste. This was added to high density polyethylene (HDPE) at varying mixing ratios and the resulting products were characterized using different experiments which included Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), melt flow index (MFI), density, wettability, tensile test, flexural test and cost analysis. The effects of various ash loadings and the use of the maleic anhydride grafted high density polyethylene (HDPE-g-MA) compatibilizer on the physical and mechanical properties of composites were investigated. It was observed that the utilization of peat ash significantly increased the tensile strength and the flexural modulus, where also reducing raw material cost. Incorporating (HDPE-g-MA) in the composites formulation led to further increases in tensile and flexural properties. Conversely, there was a significant decrease of impact strength found for all composites in comparison to the virgin HDPE. And the impact strengths generally decreased as peat ash content increases. Microstructural analyses showed that surface treated peat ash particles appeared to be well-incorporated into the HDPE matrix, as intimated polymer/peat ash contact was observed. In addition, the melt flow index of the composites decreased remarkably with an increase in peat ash content. No significant water uptake effect was detected on peat ash composites indicating that these materials could be used as a direct replacement for HDPE in applications where impact strength is not a critical factor. Furthermore, the use of peat ash increased the composite density in comparison to virgin HDPE. Nevertheless, as peat ash reinforcement does offer increased tensile and flexural properties, this may make the end product lighter as lower wall thickness parts can be used to fulfil the same function. From this study, it was concluded that the utilization of the peat ash from peat fired power stations has proved to have significant value-added potential as a filler material in polymer composites.

A new concept of equivalent inhomogeneity is proposed to facilitate analysis of effective properties of composites with interphases using techniques devised for problems without interphases. The basic idea to replace the inhomogeneity and its interphase by a single equivalent inhomogeneity (combining properties of both) is akin to previously proposed developments but the criterion of equivalency is entirely different. It is based on Hill's energy equivalence principle, and is illustrated considering spherical inhomogeneity with Gurtin–Murdoch surface model and spring layer model of interphases. The validity of the suggested technique is documented by remarkably good agreement with the best available solutions for composites containing spherical inhomogeneities with spring layer model of interphase.

Glass fiber/epoxy polymer (GFRP) composites are widely used in the aerospace engineering industry due to their high specific strength to weight ratio with non-corrosive properties, however they are very sensitive to foreign object impact. This study aims at investigating the impact response of GFRP composites at different temperature environments, which are encountered in their service at high attitude and low earth orbit (LEO) conditions. 18 GFRP samples were fabricated by vacuum infusion process and 9 of them were post-cured at 353 K for 3 h to ensure that a complete chemical reaction inside the samples was achieved. Low velocity drop weight test was performed for the samples prepared and then stored at room temperature (295 K), dry ice temperature (199 K) and liquid nitrogen temperature (100 K) conditions. The apparent damages and their size were visually examined and measured. Impact parameters such as impact load, deflection and energy absorption of each damage type were also analyzed. Besides, the post-curing effect was also studied to verify its significance to the impact properties of composites. Experimental results showed that GFRP composites at cryogenic condition exhibited smaller apparent damage and were stiffer as compared with other cases. However, they demonstrated relatively poor energy absorbability at low temperature condition. It was also found that post-curing could reduce the apparent damage and increase the energy absorption of GFRP composites.

The mechanical properties, such as strength and stiffness, of epoxy-based composites containing MWCNTs were experimentally and theoretically investigated. The classical analytic homogenization approach, called the Mori-Tanaka model, was firstly modified and reported to predict strength properties for composites containing multiple heterogeneities. In the modified Mori-Tanaka micromechanical strength modeling, the composites were considered as a two-phase simple model, as well as multiple heterogeneity case. The values obtained here were compared to experimentally measured data. The specimens reinforced with heterogeneities such as multi-walled carbon nanotubes (MWCNTs) were mainly fabricated and tested to measure the strength and stiffness of epoxy-based composites. When comparing the experimentally measured data of those composites with the predicted values obtained from the modified micromechanics models, it was confirmed that the developed approach successfully captures the effect of different types of heterogeneity on the resulting strength and stiffness of composites containing different geometrized nanofillers.

Ground tire rubber (GTR) has been used as a sustainable low-cost modifier in various composites. However, due to the hydrophobic nature of GTR, it is in compatible with most matrices and results in deterioration in both mechanical and physical properties of composites. This necessitates pre-modification of the powdered rubber to improve the interfacial bonding at the rubber-matric interface. The most common GTR modification research relies on surface etching via use of various techniques. The current review aims to give a detailed overview of the surface etching chemical modification methods for GTR for incorporation into various matrices such as concrete, bitumen and polymers. The review will serve as a guide for engineers, chemists and manufactures with interest of including GTR in any type of composite for achieving compatibility with the main matrix. The surface chemical etching treatment methods such as acid etching, hydroxylation, oxidation, and radiation methods are discussed in this work. The characterization methods to confirm the functional groups on the modified GTR and the effect of the treatment on the resultant GTR composites are also highlighted. Finally, this review highlights the advantages and limitations of the chemical surface etching processes for GTR.

Polymeric composites with the advantages of easy process, light weight and good chemical resistance were employed in thermal management. The construction of a new type thermal conductive filler has become an efficient method for improving the thermal transportation performance of polymer composite. In this work, a barnacle-like nano-crystalline diamond@silicon carbide (ND@SiC) is prepared through depositing ND on SiC powders in a hot filament chemical vapor deposition (HFCVD). ND@SiC/PVDF composite was prepared and their thermal transportation properties were investigated. The obtained composites with 70 wt% ND@SiC loading exhibit a high thermal conductivity of 2.39 W m−1 K−1, which increased by 1132% in comparison with the pure polymer. It is also much higher than that of the composite adding 70 wt% SiC powders (1.48 W m−1 K−1). The high thermal conductivity of polymer composites by adding the ND@SiC filler is mainly attributed to the novel barnacle-like structure. This work provides a new idea to significantly enhance thermal transportation properties of composites as used in advanced packaging materials.

A critical obstacle to the design of more sustainable and durable cement-based material is its relatively low flexural strength and susceptibility to brittle fracture. In this paper, a novel cement-polymer composite was developed by in-situ crosslinking polymerization of sodium acrylate monomers and the synchronous hydration of ordinary Portland cement. In-situ polymerization in cement paste can significantly shorten the initial setting time to less than 10 min and the cement hydration process is inhibited during ions dissolution and dynamic balance stage. In-situ polymerization produces the intertwined inorganic-organic network, bridging the defections of cement paste at micro-level. Due to the formation of double-network structure, as compared with OPC, the optimized design can obtain 15% improvement in compressive strength and 200% improvement in flexural strength. The monomer to cement ratio and initiator to monomer ratio are essential factors for improving mechanical properties of composites. Furthermore, molecular dynamics is utilized to investigate the structure, dynamics and mechanical properties of interfacial bonds between sodium polyacrylate molecule and cement hydrate. The carboxyl groups in the polyacrylate provides oxygen sites to accept H-bond from protonated silicate tetrahedron and neighboring water molecules. The calcium and sodium ions play bridging role in connecting oxygen atoms in functional group and oxygen in silicate chain of calcium silicate hydrate. The H-bond, O–Ca–O and O–Na–O salt bridges strengthen the interfacial bonding, which inhibits the cracking development and enhance the ductility of cement-polymer composite. Hopefully, this in-situ polymerization strategy can provide valuable insights on high-performance cement-based composite design.

The influence of measurement temperature on the high velocity (>100 m/s) impact performance was investigated for three thermosetting epoxy resin S-2 glass composite systems. These three model resins were chemically similar but have different glass transition temperatures (Tg) and molecular weights between crosslinks (Mc) through the use of different diamine curing agents (Jeffamine® D230, D400, and D2000). Impact performance was quantified by the projectile kinetic energy absorbed (KE50) as calculated from the characteristic ballistic velocity (V50) of the composites during high velocity impact. Among the resin systems, the KE50 remained essentially constant over a broad range of temperatures for each composite set and modestly increased with decreasing Mc. The superficial damage area associated with delamination showed remarkable sigmoidal behavior as a function of the testing temperature relative to the Tg (T-Tg). Damage was high for low T-Tg values (glassy resin) and decreased as the resin traversed its Tg into the rubbery region. These damage area trends were found to depend on the resin Mc, with higher Mc values resulting in lower overall damage area and a lower inflection point temperature. High speed videography of the back surface of the samples showed that lower damage areas correlated with an increased back face deflection, which enabled energy absorption with relatively less delamination. Composite mechanical tests were performed to validate the impact performance and explain the deformation mechanisms observed during impact energy dissipation. Our results illustrate the critical importance of the resin architecture and temperature-dependent viscoelastic behavior on the impact properties of composites for impact-resistance applications.

The elastic stress and strain fields and effective elasticity of periodic composite materials are determined by imposing a periodic eigenstrain on a homogeneous solid, which is constrained to be equivalent to the heterogeneous composite material through the imposition of a consistency condition. To this end, the variables of the problem are represented by Fourier series and the consistency condition is written in the Fourier space providing the system of equations to solve. The proposed method can be considered versatile as it allows determining stress and strain fields in micro-scale and overall properties of composites with different kinds of inclusions and defects. In the present work, the method is applied to multi-phase composites containing long fibers with circular transverse section. Numerical solutions provided by the proposed method are compared with finite element results for both unit cell containing a single fiber and unit cell with multiple fibers of different sizes.

Epoxy–matrix reinforced with nanodiamond (ND) particles, with ND content up to 5 wt%, were synthesized. Characterization of NDs by field emission scanning electron microscopy (FE-SEM) and Raman spectroscopy was conducted, while composites were characterized through contact angle, nanoindentation, nanoscratch and scanning probe microscopy. The assessed properties evaluated were hardness, elastic modulus, contact angle, deformation mechanisms, creep deformation, coefficient of friction and adhesion, namely. Results showed that even small additions of ND lead to significant enhancement in the hardness and elastic modulus of epoxy matrix, while properties of composites present a switch in behavior after passing a concentration threshold; this threshold was identified and discussed.

High-strain-rate compression experiments were performed on 3D MWK carbon/epoxy composites with different fiber architectures at room and elevated temperature using an SHPB apparatus. Macro-fracture and SEM micrographs were examined to understand the failure mechanism. The results show the dynamic properties increase with the strain rate and show a high-strain-rate sensitivity. Meanwhile, composites with [0°/0°/0°/0°] have higher properties. Moreover, composites show temperature sensitivity and the properties decrease significantly, especially for composites with [0°/90°/+45°/−45°]. The results also indicate composites take on more serious damage and failure with the strain rate. The failure of composites with [0°/0°/0°/0°] behaves in multiple delaminating, overall expansion and 0° fibers tearing. While that of composites with [0°/90°/+45°/−45°] is mainly interlaminar delaminating, local fibers tearing and fracture on different fiber layers. In addition, with increasing the temperature, the composite shows less fracture and becomes more plastic. The damage of matrix yielding, interface debonding and twisting of fibers increase significantly.

The high-performance carbon fiber reinforced poly(phenylene sulfide) composites were continuously fabricated using thermoplastic prepregs in a double-belt press. The effects of process velocity on the composite consolidation quality and mechanical properties were investigated. It is found that the tensile and interlaminar shear properties of composites prepared using the double-belt press are comparable to that of compression-molded composites when the process velocity is no more than 0.20 m·min −1 . The composite fracture morphologies also show different failure mechanisms between different samples and indicate that the interfacial adhesion strength may play a vital role in the mechanical properties of CF/PPS composites. Furthermore, experimental results show that the heating time above 330 °C should be over 440 s and the void content should be lower than 2.38% in order to obtain high performance CF/PPS composites.

This experimental study is concerned with the influence of metallic (Ti) and ceramic (SiC) reinforcements in an aluminumfsilicon (AlSi) alloy, when regarding tensile properties and wear behavior. Several micron sized particulate reinforced composites were produced by hot-pressing technique: AlSi–SiC and AlSi–Ti composites and AlSi-(Ti–SiC) hybrid composites. Regarding tensile properties, all composites presented higher ultimate tensile strength (UTS) than the AlSi matrix, with the highest UTS being attained by a hybrid composite (AlSi-11.25%Ti–5%SiC). Regarding wear behavior, reciprocating pin-on-plate wear tests were performed for unreinforced AlSi; AlSi–Ti composites and AlSi-(Ti–SiC) hybrid composite against a gray cast iron (GCI) counterface. The wear mechanisms for all the tested tribopairs are presented and discussed. It was observed that the wear behavior of the AlSi–Ti/GCI and also AlSi-(Ti–SiC)/GCI tribopairs are improved when compared with the AlSi/GCI system. AlSi-11.25%Ti-5%SiC hybrid composite exhibited the highest improvement in wear rate.

The main goal of this work was to evaluate the technical feasibility of almond shell flour (ASF) as wood substitute in the production of wood–plastic composites (WPCs). The effects of organically modified montmorillonite (OMMT), as reinforcing agent, on the mechanical and physical properties were also investigated. In order to improve the poor interfacial interaction between the hydrophilic Lignocellulosic material and hydrophobic polypropylene matrix, maleic anhydride grafted polypropylene (MAPP) was added as a coupling agent to all the composites studied. In the sample preparation, OMMT and ASF contents were used as variable factors. The morphology of the specimens was characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The results of mechanical properties measurements indicated that when 3 wt.% OMMT were added, tensile and flexural properties reached their maximum values. At high level of OMMT loading (5 wt.%), increased population of OMMT lead to agglomeration and stress transfer gets blocked. The addition of OMMT filler decreased the water absorption and thickness swelling of composites. SEM study approved the good interaction of the almond shell flour with the polymer as well as the effectiveness of OMMT in improvement of the interaction. TEM study revealed better dispersion of silicate layers in WPCs loaded with 3 wt.% of OMMT. The improvement of physico-mechanical properties of composites confirmed that OMMT has good reinforcement and the optimum synergistic effect of OMMT and ASF was achieved at the combination of 3 and 50 wt.%, respectively. The findings indicated that almond shell as agro-waste material is a valuable renewable natural resource for composite production and could be utilized as a substitute for wood in composite industries.