Search

Shape memory composites now have a wide range of applications in aerospace, medical devices, and smart structures. Seven graphene‐carbon oxide/glass fiber (GO‐CF/GF) hybrid reinforced shape memory composites were prepared using vacuum infiltration hot pressing system (VIHPS) and the shape memory properties of the materials were investigated in 100°C test. By comparing and analyzing the microstructure and shape memory properties of composites containing different volume fractions of GFs, the mechanism of the influence of different hybrid contents of GFs on the organizational properties and shape memory properties was investigated. The results show that when the reinforcement of the composites were all carbon fibers, the composites had the largest elasticity modulus, harder material and the fixation rate of 77.15%, the recovery rate of 95.17%, the porosity of 0.80% and the shape recovery force of 7.98 N. When the reinforcement of the composites were glass fibers, the composites had the smallest elasticity modulus, softer material and the fixation rate of 94.89%, the recovery rate of 77.21%, the porosity of 13.56% and the recovery force of 2.28 N. The results of this test can lay a foundation for subsequent research on fibers with different mixing ratios. Highlights: The GO‐CF/GF/EP prepared by VIHPS has excellent shape memory properties.Fiber hybrid ratio affects the composite's porosity and its properties.Fiber hybrid ratio affects the composite's shape fixation, recovery, and memory force.The shape fixation of G6 decreases the lowest with test cycles.Carbon fiber content changes the zero‐stress plane of GO‐CF/GF/EP. [ABSTRACT FROM AUTHOR]

Unidirectional fiber‐reinforced composite laminates have limited resistance to out‐of‐plane impact and are prone to structural integrity damage during service due to low‐velocity impact (LVI). In this study, the hot‐press fusion method was employed to repair the impact‐damaged unidirectional carbon fiber‐reinforced poly‐ether‐ether‐ketone (CF/PEEK) thermoplastic composites. No delamination or matrix cracking induced by impact was observed in the repaired specimens, as confirmed by ultrasonic scanning and digital microscope. In addition, the hot pressing treatment enables the fibers to be covered again by the resin matrix, which eliminates fiber pull‐out and fiber/matrix debonding. Afterward, typical responses of CF/PEEK composite laminates to re‐impact and post‐repair compression are presented in a comprehensive and detailed manner, and compared with the initial impact response and compression after impact (CAI) behavior. The effects of three impact energies and two stacking sequences are considered. The results indicate that quasi‐isotropic laminates are more susceptible to localized fracture damage upon re‐impact as the impact energy increases, due to initial fiber breakage, compared to orthotropic laminates. The hot‐press treatment enhances the compression residual strength of the specimen by 20%–30% compared to its state before repair. These studies offer technical insights into the application of the hot‐press fusion method to enhance the mechanical properties of composite laminates post impact damage. [ABSTRACT FROM AUTHOR]

The incorporation of high dielectric constant filler particles into thermoplastics is an attractive approach to develop materials with high dielectric strength, low dielectric loss, and mechanical stiffness, for electronic packaging purposes. Herein, we report the preparation and properties of polystyrene (PS) based low loss 0–3 composites with inorganic PbZr0.3Ti0.7O3 (PZT) filler particles in concentrations ranging from 0%–20% (w/w). The PZT particles were synthesized using the sol‐gel process and the composites were prepared by a two‐step, solvent‐free approach: (1) melt mixing, followed by (2) hot press. The thermal and mechanical properties of the composite samples were investigated. The dielectric behavior of the as‐synthesized composites showed pronounced improvement over pure PS, as is seen from the increased dielectric constant and extremely low loss tangent. For 20 wt.% PZT loading, the dielectric constant of the composite is as high as 12 at 1 MHz frequency, which is about five times greater than that of pure PS (ε = 2.5). All the PZT/PS composites exhibit remarkably low dielectric losses, even at lower frequencies (tan δ ≤ 0.04), which is better than reported literature values of PS based composites. The variation in dielectric constants of the samples with increasing temperatures was also recorded. [ABSTRACT FROM AUTHOR]

Highlights In the present work, bio‐based phenolic matrix composites (PMCs) were fabricated by reinforcing them with bi‐directional glass fiber mats, bi‐directional Kevlar fiber mats, and their hybrid combinations. Both fiber mats were treated with (3‐glycidyloxypropyl) trimethoxysilane (GPTMS) to enhance fiber‐to‐matrix adhesion. Subsequently, the fibers were coated with a phenolic binder made from a mixture of phenol‐hexamine‐based novolac (N) resin and cardanol‐hexamine‐based benzoxazine (Bz) resin. Then the layers of binder‐coated fibers were compressed using a hot press molding machine at 200°C to cure the resins. The developed composites were subjected to thermogravimetric analysis (TGA) and UL‐94 V flammability test. The glass fiber (GF‐NBz) and Kevlar fiber (KF‐NBz) reinforced PMCs show an overall mass loss of ~18.5% and 66% at 850°C. Whereas the hybrid GF/KF fiber‐reinforced PMCs exhibit balanced properties of improved thermal stability and higher char yield. The flammability test results show both pure and hybrid samples exhibited a V‐0 rating. Based on these observations, the combination of glass fiber and Kevlar fiber‐reinforced PMCs may be suitable for automotive applications, such as dashboards, and door panels, with improved performance and fire safety. Glass and Kevlar/phenolic and their hybrids were developed using hot press. Fibers coated by (3‐glycidyloxypropyl) trimethoxysilane to enhance bonding. GF/KF composites exhibited balanced properties in thermal property. The pure and hybrid samples achieved a V‐0 rating under UL‐94 V test. [ABSTRACT FROM AUTHOR]

Highlights Double‐vacuum‐bag (DVB) process, as an effective out‐of‐autoclave (OoA) technology, can manufacture composite materials with low void content and high mechanical properties. Therefore, this paper aimed to achieve low void content, the effects of pressure difference between inner and outer bags, dwelling temperature, and dwelling time on the void of composite laminates were studied based on orthogonal experimental method. The void content and morphology of laminates were statistically analyzed, by observing the microscopic images of the samples on cross‐section. The results show that the pressure difference between the inner and outer bags has a significant impact on the void content and morphology, while the dwelling temperature and dwelling time have little effect. In addition, with the variance analysis and extreme difference analysis, the optimal process parameters were determined as follows: pressure difference between inner and outer bags was 0 MPa, dwelling temperature was 110°C, and dwelling time was 15 min. The void content of composite laminates manufactured under these parameters is 0.07%, less than 1% requirement for aerospace components, and interlaminar shear strength (ILSS) is 110 MPa, which is 54.93% higher than the single‐vacuum‐bag (SVB) process. Generally, the void content and ILSS reached the level of hot press process with 0.6 MPa. Influence of different DVB process parameters on void were studied. Void content manufactured with the optimal DVB process parameters was less than 1%. ILSS of laminate with the optimal DVB process parameters was equal as hot press process. [ABSTRACT FROM AUTHOR]

In the present study, experimental and numerical investigations are carried out on Vanadium dioxide (VO2)-UHMWPE composite plates while considering the temperature across phase change. VO2 is known for semiconducting to metallic transition along with structural changes from monoclinic to tetragonal during heating above 68°C, which enhances structural stiffness. For the experimentation, VO2-UHMWPE composite samples are fabricated by employing the Hot-Press method. These samples are further utilized to perform the compression test in order to find Young's moduli at room temperature (RT) and 75°C (temperature across phase change) using a Universal Testing Machine (UTM). Based on the experimentally computed Young's moduli, the numerical investigations in terms of free vibration and bending analyses, are performed. For structural kinematics, a C0-continuous higher-order shear deformation theory (HSDT) is employed, and the governing equations are derived using the Lagrange model. The numerical results, that is, natural frequencies and center deflection, are assessed using the finite element method (FEM). The convergence and comparison studies are accomplished to ensure the performance and competence of the present numerical model within the framework of MATLAB and ABAQUS. The influence of temperature, thickness ratio, boundary conditions, etc. on the frequency and deflection of the bare UHMWPE polymer and VO2-UHMWPE plates, is discussed in detail. Based on the results, it can be concluded that the VO2 reinforcement to the UHMWPE polymer improves structural stiffness at a temperature of 75°C. Moreover, VO2-UHMWPE composite can be utilized for structural applications, wherein lightweight and high-temperature resistive material is desired. Highlights • The fabrication of the VO2-UHMWPE composite samples is accomplished through the Hot-Press method. • Young's moduli of the VO2-UHMWPE composites at RT and 75°C are assessed utilizing UTM. • The finite element method is employed to analyze the behavior of the bare UHMWPE polymer and VO2-UHMWPE plates in free vibration and bending. • The effect of influencing parameters such as temperature, thickness ratio, boundary conditions, etc., on natural frequency and deflection of the plates are explored. [ABSTRACT FROM AUTHOR]

This article presents efficient methods to manufacture, thermoform, and recycle sandwich composites consisting of glass fiber (GF)/polyethylene terephthalate (PET) composite skins and a PET foam core. Sandwich composite panels were manufactured using a hot press, which involved heating and pressing from the upper and lower platens inducing thermal fusion between the skin and the foam core. The formability of the sandwich composite panels using a hot press and a pocket‐shaped mold was simulated to determine the forming conditions. And the formability of the sandwich composite panels was tested using the simulation results. Recycling of the sandwich composite panels was achieved using recycling molds to perform heat compression. The excess PET was separated from the GF/PET composite and re‐impregnated with the remaining GF and PET. As a result of recycling, recycled PET and PET/GF composite were obtained. Design of experiments (DOE) analysis was conducted to analyze the recycled properties and to identify which factors affected these properties. These results were re‐plotted according to DOE priority ranking to identify the changes in the properties of the recycled materials per factor. Compared to the original properties, the mechanical and thermal properties including modulus, ultimate tensile strength, melting temperature and crystalline temperature were ~ 95 and ~ 99% preserved. These findings are expected to contribute towards the development of recyclable sandwich composite panels with reduced mass production cost, which are easily formed, used and recycled. [ABSTRACT FROM AUTHOR]

Thermally conductive polymeric composites with low dielectric constant are highly promising for the packaging materials in the field of modern communication. Therefore, the synergistic improvement of low dielectric constant and high thermal conductivity has become a current research hotspot. In this work, we propose a one‐step alkylation of boron nitride nanosheet (BNNS) with ultrasonic stratification using 1‐hexanol, and then hot press the films to make Alkyl‐BNNSs orient in the fluorinated polyimide (f‐PI). The resulting Alkyl‐BNNS/f‐PI composite successfully realizes the synergistic improvement of thermal property and dielectric properties, exhibiting a high heat conductivity coefficient of 2.36 Wm−1 K−1 with a filler content of 4.99 wt.%. Moreover, the permittivity and dielectric loss of the film are as low as 1.76 and 0.0065 at 1 MHz, respectively. This work provides a facile strategy for breaking the bottleneck of making polyimide composites simultaneously with high thermal conduction and low dielectric performance. Highlights: The composite exhibits a high heat‐conducting coefficient of 2.36 Wm−1 K−1.Ultra‐low dielectric constant of 1.76 was achieved by the modification of film.Excellent breakdown resistance and flexibility were endowed with the composites. [ABSTRACT FROM AUTHOR]

Natural fiber‐reinforced composites exhibit excellent mechanical properties. However, achieving a balance between excellent mechanical properties and optimal acoustic performance remains a challenge. In this study, four composite laminates with different stacking orders were fabricated using polyester fiber mats (WFs) and palm sheaths (WPs) through a hot‐press process. Moreover, the effects of different stacking orders on the mechanical and acoustic properties of the composite were investigated. The results revealed that the incorporation of polyester fiber felts and the modification of the layup sequence of WP and polyester fiber felts significantly improved the mechanical and acoustic properties of the composites. Scanning electron microscopy images revealed a strong bonding between palm fibers and polyester fibers at the epoxy resin interface. Compared with pure palm fiber composites, the alternately stacked palm fibers and polyester fibers (WP/WP/WF/WP/WF) exhibited the highest mechanical properties, with a significant enhancement of 142.67% and 16.90% in flexural and tensile strengths, respectively. Additionally, the peak absorption coefficient of polyester fiber felts, positioned in the surface layer of the composite material, within the 2580–3400 Hz frequency band significantly increased from 0.07 to 0.44. Therefore, this study indicates that modifying the stacking order improves the mechanical and acoustic properties of the composites, making them suitable for use in acoustic engineering materials for buildings and decorative panels for furniture, including perforated panels and acoustic screens. Highlights: The fabric‐like textured structure significantly enhanced the overall performance of the composites.The stacking order significantly influenced the overall properties of the composite.Alternately stacked polyester fiber felts and palm fibers exhibited excellent mechanical performance.The polyester fiber felts positioned on the surface layer of the composites exhibited superior mechanical performance.A laminate with "green" attributes and good acoustic properties was fabricated. [ABSTRACT FROM AUTHOR]

In the present study, a positive‐pressure filtration method was proposed to prepare carbon nanotube buckypapers (CNT BPs) with desirable porosity and mechanical properties. The obtained BPs were then infiltrated with epoxy via vacuum‐aided resin transfer molding (VARTM) process without the use of a solvent. Some of the impregnated composites were directly cured under a vacuum pressure. The others were put into a hot‐press to cure under a higher pressure of 0.7 MPa. Results have shown that the tensile strength and modulus of the vacuum cured composites were obtained as 215 MPa and 13.3 GPa, whereas these two values could reach 319 MPa and 20.3 GPa, respectively, for the hot‐press cured composites. The glass transition temperature of the hot‐press cured composites was also improved by 7% compared with that of the vacuum cured composites. Furthermore, SEM observation revealed that the BPs were infiltrated well with epoxy and good interfacial bonding between CNTs and epoxy was obtained. This study has demonstrated that the random aligned CNT BPs reinforced epoxy composites possessing desirable mechanical properties can be fabricated by using conventional processes when the microstructure of the BPs is improved. POLYM. COMPOS., 39:1647–1654, 2018. © 2016 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

To investigate the effect of alumina on the thermal, mechanical, and tribological properties of resin‐based friction materials, five friction materials with different alumina contents were prepared by the hot press molding process. The experimental results showed denser friction materials possessed higher hardness, while compressive strength and compression modulus dropped as alumina decreased. Friction material with 6 wt% alumina exhibited outstanding impact strength and great heat resistance. It also showed excellent friction stability, with a maximum mean coefficient of friction (COF) steady between 0.408 and 0.425 at various braking speeds. The wear resistance of friction materials had a positive relationship with the stability of the COF, and the greater the stability of the COF, the better the wear resistance and the lower the corresponding wear rate. The morphology of the worn surface indicated multiple sources of friction at different braking speeds, and large areas of dense friction films were beneficial to stabilizing the COF and reducing the wear rate. Highlights: The sample with 6 wt% alumina showed excellent heat resistance, with a residual value of 83.5% at 800°C.The highest compressive strength and compression modulus were achieved in the sample with 8 wt% alumina.The sample containing 6 wt% alumina exhibited the highest COF and the lowest wear rate.The maximum subsurface temperature of the friction materials basically rose as braking speed increased.Large areas of dense friction films were beneficial to stabilizing the COF and reducing the wear rate. [ABSTRACT FROM AUTHOR]

Highlights This study investigates the development of a novel biocomposite tailored for sustainable packaging applications, integrating cellulosic woven fiber mats into poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV), a biocompatible polymer. Utilizing hot press compression molding, composite boards with a thickness of 3 mm were fabricated. The cellulosic fiber mats were chemically modified with propionic anhydride, enhancing their compatibility with the PHBV matrix. Varied concentrations of reinforced propionylated cellulosic fiber mats (10%, 20%, 30%, 40%, and 50%) were investigated. The propionylated cellulosic abaca fiber composites exhibited superior functional properties, thermal stability, biodegradability, and mechanical performance compared to pure PHBV matrix. Notably, mechanical properties showed significant improvement with increased cellulosic fiber content, particularly achieving optimal strength at 30 wt% reinforcement. Chemical treatment enhanced interfacial bonding, evident in higher water contact angles and confirmed by Field Emission Scanning Electron Microscopy (FE‐SEM) analysis. The biodegradation rate of biocomposites was faster compared to the control PHBV biopolymer. Despite potential agglomeration issues at higher concentrations, PHBV/chemically modified cellulosic fiber composites hold promise as sustainable packaging materials, contributing to a greener future in packaging applications. Successful preparation of PHBV composites with treated plant fibers. Propionic anhydride treatment enhances fiber‐PHBV bonding and water resistance. Improved strength at 30 wt% treated abaca fiber in PHBV composites. Propionylated fibers enhance biodegradability compared to pure PHBV matrix. Promising sustainable packaging with chemically modified cellulosic fibers. [ABSTRACT FROM AUTHOR]

This study investigates the mechanical properties and erosion resistance of high temperature–pressure carbon‐epoxy novolac insulation reinforced with ZrB2/SiC particles. For this reason, at first, five samples were fabricated using the hot press, which included resin epoxy novolac EPN1180 base without reinforcement and four samples containing resin with 20:80, 30:70, 40:60, and 50:50 of SiC: ZrB2 particles respectively. After manufacturing of the samples, the mechanical properties were evaluated through bending and tensile testing, followed by erosion resistance properties by the use of oxyacetylene flame erosion tests. Chemical composition and surface morphology analysis of the composites were conducted using energy‐dispersive spectroscopy, scanning electron microscopy, and x‐ray diffraction analysis. Results indicate that the addition of ceramic particles enhances both mechanical properties and erosion resistance of the composite. The pure resin sample exhibited the highest weight loss and thickness reduction, while the sample containing 40% SiC and 60% ZrB2 demonstrated the least weight loss and thickness reduction about 55% and 83% respectively compared to pure sample. Additionally, the sample with 30% SiC and 70% ZrB2 had the lowest backside temperature. Furthermore, the sample with 20% SiC and 80% ZrB2 exhibited the highest mechanical properties, with a tensile strength of 422.5 MPa and flexural strength of 587.11 MPa. Morphological analysis revealed the presence of phases such as SiO2, ZrO2, and ZrSiO4 attributable to the ZrB2/SiC particles, contributing to the enhancement of erosion resistance. Highlights: Examines volume ratios of ZrB2/SiC.Discovers the best particle ratio (20%SiC, 80%ZrB2) for mechanical properties.Identifies the best particle ratio (30% SiC, 70% ZrB2) for erosion resistance.Reveals key phases enhancing erosion resistance with advanced analysis methods.Linear and mass ablation rate improved by 83% and 55% (best formation). [ABSTRACT FROM AUTHOR]

Highlights With the increasing complexity of radiation environments, the development of effective shielding materials against 222Rn and gamma radiation is critical for ensuring human health and safety. This study utilized a two‐step hydrothermal method to synthesize Gd₂O(CO₃)₂@bismuth‐based metal–organic frameworks (Bi‐MOFs)/graphene nanoplatelets (GBG) composite fillers, followed by melt blending and hot‐press molding to develop GBG/polymethyl methacrylate (PMMA) composites aimed at shielding against 222Rn and gamma radiation. The successful synthesis and structural integrity of the composites were confirmed using various characterization techniques, including x‐ray diffraction, Fourier‐transform infrared spectroscopy, scanning electron microscopy, and energy‐dispersive x‐ray spectroscopy. The experimental results indicate that the GBG composite filler exhibits superior enhancement in 222Rn shielding capabilities, with the 222Rn diffusion coefficient of GBG/PMMA‐20 composites reduced to 1.41 × 10−13 m2/s, a 98.6% decrease compared to pure PMMA (1.04 × 10−11 m2/s). Furthermore, the GBG demonstrates outstanding improvements in gamma‐ray shielding performance, with the mass attenuation coefficient of GBG/PMMA‐50 reaching 2.70 cm2/g for 59.5 keV gamma rays, nearly 16 times higher than that of pure PMMA (0.16 cm2/g). Additionally, thermogravimetric analysis revealed that the introduction of GBG fillers significantly improves the thermal stability of the PMMA composites. This work could offer an innovative approach to the design of 222Rn and gamma radiation shielding materials. Developed a novel composite for enhanced 222Rn and gamma radiation shielding. Introduced Gd‐based fillers to enhance gamma radiation attenuation in PMMA composites. Achieved superior thermal stability in PMMA composites compared to pure PMMA. Materials designed for application in high‐radiation environments, including mining. [ABSTRACT FROM AUTHOR]

The quasi‐static tensile properties of carbon nanotube (CNT) composites have already been extensively studied, while their impact tensile properties under high rates have rarely been investigated. In this work, CNT film/PVA composites were prepared by impregnation and hot press curing, whereas CNT films were prepared by floating catalyst chemical vapor deposition (FCCVD). Instron 3365 and the miniaturized split Hopkinson tensile bar (SHTB) were used for tensile tests at various strain rates. The results show that the tensile properties of PVA‐impregnated CNT film are significantly improved, and the strain rate effect is remarkable. The tensile properties are best when the mass fraction of PVA is 1.5%. At a low strain rate of 0.001 s−1, the maximum stress and energy absorption (EA) of CNT composites are 502.5 MPa and 63.6 MJ/m3, respectively. And at the high strain rate of 3100 s−1, the maximum stress and EA of CNT composites are 969.0 MPa and 166.4 MJ/m3, respectively. Scanning electron microscopy (SEM) was used to observe the failure morphologies at tensile fracture of composites under different strain rates. At low strain rate, the failure mode is the pulling fracture of tube bundles and the crushing of polymers, while at high strain rate is the folding and spring back of tube bundles, as well as the debonding of polymers. [ABSTRACT FROM AUTHOR]

This study aims to investigate the effects of blending cashew nutshell oil modified phenolic resin and nitrile rubber (NBR) on the thermal, mechanical, and tribological performance of brake friction materials. The friction materials, which have a total binder of 25 wt% and different ratios of cashew nutshell oil modified phenolic resin and NBR, were prepared by hot press molding process. The experimental results show that NBR is beneficial to improve the hardness and compression modulus of the brake friction materials. The coefficient of friction (COF) is proportional to the wear rate, when the ratio of cashew nutshell oil modified phenolic resin and NBR is 13:12, the friction material has good heat resistance and exhibits excellent friction stability in the braking process, and the COF is steady between 0.420 and 0.448 at different braking speeds, while the wear resistance of material is optimal. The worn surfaces of the friction materials were examined by scanning electron microscope, and it was determined that the friction film is predominantly secondary plateaus, which can stabilize the COF and reduce the wear rate. [ABSTRACT FROM AUTHOR]

In this study, basalt and/or beech wood fibers were treated with vinyltrimethoxysilane or compatibilized by maleic anhydride‐ grafted polypropylene (MAPP) to produce hybrid polylactic acid (PLA) biocomposites. Twin‐screw extruder was used to produce biocomposites, following by a hot press to form samples. Physical and mechanical properties of composites that were produced from both treated and untreated fibers were compared. Chemical, morphological, and thermal analysis of biocomposites were analyzed with TGA, FTIR and SEM, respectively. The results showed that silane treated basalt/wood fiber reinforced PLA (PBWS) and silane treated basalt reinforced PLA (PBS) have significantly better flexural strength than neat PLA. Besides, basalt reinforced bio‐composites except PBW3 and PBWM variations have significantly superior impact strength than neat PLA. Utilization of compatibilizers also reduced thickness swelling and water uptake features of biocomposites. All the above experimental data showed that the utilization of silane compatibilizer has better impact on properties than MAPP for such wood/basalt hybrid composite. Highlights: Hybrid biocomposites with wood and basalt fibers by using coupling agents were prepared for the first time.Hybridization of organic and inorganic fibers gave promising results.Silane and maleic anhydride compatibilization improves physical properties.Vinyltrimethoxy silane grafted basalt fiber improves flexural strength significantly.Silanization of wood or basalt fibers enhances significantly the impact strength. [ABSTRACT FROM AUTHOR]

The expanding realm of high‐frequency electronics necessitates materials with exceptional attributes: notably, a low dielectric constant (Dk) to minimize signal propagation delays, high thermal conductivity for effective heat dissipation, higher breakdown strength, and robust mechanical properties to withstand demanding operational environments. While cycloolefin copolymers (COC) excel in electrical insulation, chemical resistance, and mechanical durability, their intrinsic slightly higher dielectric constant compared to other polymers, along with challenges such as poor dispersibility and low compatibility with nanoparticles, hinder their full potential in this domain. Considering these drawbacks, this study fabricated a series of COC/mica composites by integrating natural mica particles into the COC matrix via a CTAB‐assisted surface modification of mica to enhance dispersibility and mitigating particle aggregation through in‐situ mixing and hot‐press methods. The resultant composites demonstrate an outstanding ultra‐low Dk of 1.44, marking a significant decrease of over 36% compared to pristine COC with a Dk of 2.26, along with exceptionally low dielectric loss (δ) of 0.00013 at the frequency of 10 GHz, high dielectric breakdown strength ~49.40 kV/mm and enhanced thermal conductivity up to 0.88 W/(m K) at 40% mica loading. Additionally, the composites heightened mechanical performances like tensile strength 69 MPa at 6.5% elongation at break, impact strength up to ~17.9 kJ × m−2, and exceptional water resistance with absorption below 0.097%. These exceptional ultra‐low dielectric performance with above mentioned properties can meet the stringent requirements of modern high‐frequency electronics packaging for next generation electronics development. Highlights: Surface modification by CTAB enhanced homogeneous dispersibility of composites.Achieved ultra‐low dielectric constant and loss compared to pure COC.Thermal conductivity improved significantly with incorporation of mica.Unlocking high‐frequency applications potential with ultralow Dk performance. [ABSTRACT FROM AUTHOR]

In this paper, five groups of graphene oxide‐carbon fiber/epoxy resin (GO‐CF/EP) composites with different curing temperatures were prepared by the vacuum infiltration hot‐press system (VIHPS). These five groups of composites presented satisfactory macroscopic morphologies. However, the microstructure of the GO‐CF/EP composite cured at 110°C was satisfactory because there was no obvious infiltration defect. The damping properties of these composites were tested by force hummer method. When the curing temperature was 110°C, the composite had a maximum damping ratio of 0.21%, while the composite cured at 130°C had a minimum damping ratio of 0.13%, which decreased by 35.89%. In addition, when the curing temperature was higher, the damping properties of the composite were also worse than that of the composite cured at lower temperature. Because the curing temperature was different, the infiltration effect of resin in the fiber was various, and the energy dissipation ways in the composite material was different, which was reflected in the damping properties. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) of continuous fiber‐reinforced thermoplastic composites (CFRTPCs) has drawn increasing interest and great attention in academic and industrial communities due to its capability of manufacturing complex lightweight structures with high strength at a low cost. In this study, we proposed a novel AM technique to fabricate CFRTPCs using carbon fiber prepreg sheets based on a novel method: ultrasonic‐assisted laminated object manufacturing (UA‐LOM). The prepreg sheets were first cut into 2D shapes, then every eight layers of the sheets were successively consolidated by an ultrasonic‐vibration roller to fabricate one 3D composite part at a faster speed than conventional AM processes where materials are deposited layer by layer. Samples with controlled fiber alignments were prepared for mechanical tests. The post‐processing hot press was carried out to further improve mechanical properties of the additively manufactured components. Results showed that the unidirectional composite samples displayed an ultra‐high tensile strength of 1760.2 (±71.7) MPa and a tensile modulus of 105.7 (±7.2) GPa. The proposed method exhibited superior mechanical performance compared to state‐of‐the‐art AM techniques. The hot‐press‐treated AM composite parts in this work approached the benchmark mechanical properties provided by the prepreg manufacturing company using traditional fabrication methods. Overall, the proposed AM methods of CFRTPCs show great potential applications in aerospace and transportation industries. [ABSTRACT FROM AUTHOR]

In this study, natural fiber‐reinforced polymer nanocomposites were prepared from high‐density polyethylene (HDPE), abaca fiber, and nanoprecipitated calcium carbonate (NPCC) using the hot press technique. The study investigated the influence of untreated and alkali‐treated woven abaca fabric and NPCC hybrid reinforcement on the thermomechanical behavior of the natural fiber composites. The HDPE with different amounts of NPCC was melt‐blended in a twin‐screw extruder followed by hot press to produce sheets. A lamination of composites containing alternating layers of HDPE sheets with different amounts of NPCC and layers of untreated and alkali‐treated woven abaca fabric was produced using a hot press machine. The resulting material was composed of 20% weight ratio of woven abaca fibers. The tensile strength showed that the nanocomposite exhibited a high tensile value of 60.1 MPa with alkali‐treated abaca and 1% NPCC. However, a further increase in the NPCC concentration beyond 1% reduced the mechanical strength of the nanocomposite. The thermal stability of the abaca fiber‐reinforced nanocomposite improved with addition of NPCC. Scanning electron microscopic analysis demonstrated that alkali‐treated abaca and 1% NPCC improved the adhesion and compatibility between the fiber and polymer matrix. The potential applications of this natural fiber‐reinforced composite are for automotive and construction materials. [ABSTRACT FROM AUTHOR]

Development of shielding materials for 222Rn and γ radiation has crucial implications for ensuring the safety of individuals. This paper reports the synthesis of modified graphene nanosheets (MGNPs) via the reaction of KH560 with graphene nanosheets (GNPs), while melt blending and hot‐press molding technique were used to fabricate a multifunctional polymer composite shielding material, MGNP/WB/PMMA (polymethyl methacrylate). Successful synthesis of MGNP was confirmed by Fourier transform infrared spectroscopy, and scanning electron microscope (SEM) analysis was utilized to assess the distribution of functional fillers within the cross‐section of the polymer composite. Additionally, thermogravimetric analysis (TGA) demonstrated that MGNP and WB particles enhance the thermal stability of the polymer composite materials. Compared to pure PMMA, 98.7% decrease in the radon diffusion coefficient was observed for MGNP1.5 wt%/PMMA composite material. In addition to enhance the radon‐blocking characteristics of the polymer composites, inclusion of WB particles also boosts their shielding capacity against gamma radiation. The 222Rn diffusion coefficient of MGNP1.5 wt%/WB25wt%/PMMA polymer composite material decreased by 99.6% and at energies of 60 KeV, 80 KeV, 122 KeV, 365 KeV, the mass attenuation coefficient (MAC) for the composite material increased by 0.79, 1.97, 0.57, and 0.05 cm2/g, respectively, compared to pure PMMA. Highlights: The PMMA composite materials doped with graphene nanosheets demonstrate outstanding resistance to 222Rn.Graphene nanosheets modified by KH560 exhibit favorable dispersion within PMMA.WB can further enhance the radon resistance of MGNP/WB/PMMA composite materials.The polymer composites exhibit excellent 222Rn and gamma ray shielding properties. [ABSTRACT FROM AUTHOR]

This study investigated the effect of cyclic tests on the shape memory performance of graphene oxide‐carbon fiber (GO‐CF) hybrid‐reinforced shape memory polymer composite (SMPC). The shape memory performance was evaluated by four indexes: shape fixation rate, shape recovery rate, recovery time, and maximum recovery force. The results showed that the service life of the GO‐CF hybrid‐reinforced SMPC prepared by the vacuum infiltration hot‐press forming experimental system process (VIHPS) was 16 cycles. After 16 repetitions, the shape fixation rate decreased by approximately 6.6% and the shape recovery rate decreased by approximately 14.0%. At this time, the shape recovery rate was lower than 90%. The recovery time increased by 62.2% and the maximum recovery force decreased by 70.1%. The maximum recovery force exhibited the highest performance attenuation. Scanning electron microscopy (SEM) was used to photograph and analyze the microstructures of the samples under various cyclic tests. It was concluded that the main factor affecting the shape memory performance of GO‐CF hybrid‐reinforced SMPC is the life of fiber bundle. During cyclic testing, the fiber was prone to kinks, tensile damage and other defects, which increased the probability of reducing the length of the fiber bundle. Therefore, the probability of fiber fracture was improved, and the shape memory performance of the GO‐CF hybrid‐reinforced SMPC was attenuated. [ABSTRACT FROM AUTHOR]

The primary purpose of this study is to realize quantitative fiber loading effects on free vibration, damping behavior, fracture toughness, thermal conductivity, inter‐laminar shear strength, and flammability of jute–banana fiber phenol‐formaldehyde (PF) hybrid composites. These composites were manufactured with fiber weight percentages ranging from 30% to 60% using hot press technique. Hybrid composite with equal amount of fiber and resin (PJB‐2) had a higher natural frequency in the range of 4.8%–59%, a higher inter‐laminar shear strength varying from 30% to 54%, a higher fracture toughness with minimum of 19 to maximum of 44%, and a low damping factor in the range of 25%–59% to that of other composite having unequal amount of fiber and resin loading. In contrast to other composites, the composite containing 30 wt% fiber (PJB‐4) has a high heat conductivity of about 10%–20%. However, the thermal conductivity of jute–banana fiber PF composites declined as the fiber content increased beyond 30 wt%, while the flame resistance was improved as the resin concentration increased. Additionally, Scanning electron microscopy (SEM) studies clearly indicates the failure patterns of fiber matrix interface under Inter laminar shear strength and fracture toughness tests were supports to justify the experimental results. [ABSTRACT FROM AUTHOR]

This study aims to investigate the thermo‐physical and morphological morphology of cornhusk fiber‐reinforced polyester composites. The content of corn husk fiber (CHFs) has been varied, namely 20, 30, 40, and 50 (% vol.) in the polyester composite, respectively. The hot press technique has been used in the manufacture of these composites, then properties were investigated through thermo‐physical tests including differential scanning calorimetry, thermogravimetry, Fourier transforms infrared, impact strength properties, and morphology using SEM. The results showed that the composite containing 30% CHF (KJP2) was found to have the most optimal impact strength (4.25 KJ/m2), and the best thermal resistance properties were found in the KJP3 composite, compared with other composites; due to CHF dispersion and good interfacial adhesion between CHF and polyester. SEM images of the fracture of the impact test specimens of the composites show better interfacial bonding between CHFs and polyester. [ABSTRACT FROM AUTHOR]

Thanks to their superior mechanical properties, polymer matrix composites have gained considerable importance. In order to improve the impact resistance of polymer matrix composite materials, a new hybrid material known as fiber metal laminate (FML) has been developed. The aim of this study was to reveal the effect of stacking sequence (SS), metal volume fraction (MVF), and number of layers on ballistic resistance in fiber metal laminates (FMLs). Four types of FMLs in different sequences and MVF (25% and 50%) were produced with hot press and vacuum. Ballistic tests were carried out with a single stage gas gun system. The absorbed energy was calculated from the energy difference that occurred by taking into account the FMLs entry and exit velocity of the projectile and the projectile mass. Damage types were examined after ballistic testing. It was determined that the stacking sequence and MVF significantly affect the impact resistance of FMLs. It was determined that the metal layer, which first encounters the projectile, compared to the polymer matrix composite, is more effective on the impact resistance of FMLs, and the impact resistance increased with the increase of MVF. In addition, the increase in the number of layers, if the top layers remain the same, adversely affected the impact resistance. It was observed that the first layer that encounters the projectile and the amount of MVF have a significant effect on the ballistic impact strength. As the amount of MVF increases, the ballistic impact resistance increases. [ABSTRACT FROM AUTHOR]

Eco‐friendly composite made of Timoho Fiber (TF) continuously developed to get the best performance to replace plastic‐based synthetic fibers. This study focuses on investigating physical characteristics, mechanical properties, thermal analysis, and the morphology of TF‐reinforced polyester composites by adding organic (egg shell powder‐ESP) and inorganic (aluminum powder‐AP) fillers. Hot press method was used in the composite fabrication with considered volume fraction of TF, organic, and inorganic fillers. The results showed that the density of TF‐polyester composites decreases with the increasing volume fraction of the fibers. For additional fillers, it was shown that AP was more effective to be used to improve density than ESP. The tensile and impact strength of the composite increased with increasing TF volume. However, the addition of ESP and AP fillers into the composite caused different mechanical characteristics. Filler addition increased the elasticity modulus, toughness, thermal resistance increased, while the tensile strength decreased. ESP and AP fillers provided the best thermal resistance due to the relatively high thermal conductivity of ±1700°C compared to composites without fillers and amorphous ESP fillers. SEM observation supported the analysis of TF‐polyester composite mechanical characteristics. [ABSTRACT FROM AUTHOR]

Hybrid composites have become the focal point of research communities due to the balance in mechanical and ecological properties of such materials. Hybridization is an efficient technique to strengthen and enhance the performance of composite materials. In this research study, hybrid composites were prepared by embedding pineapple leaf and glass fibers in polypropylene polymers via the hot press molding compression technique. Mechanical tests were carried out to determine the tensile, flexural and Charpy impact properties of pineapple leaf/glass fiber‐reinforced hybrid composite laminates. Additionally, water absorption test was also conducted to investigate the influence of hybridization on the moisture uptake of hybrid composites. In accordance with the findings obtained, the hybridization of pineapple leaf with glass fibers was found to improve the mechanical properties and moisture uptake sensitivity of the composite laminates. The [G/P/G] composite laminates are especially promising, having comparable mechanical strengths to those of non‐hybrid [G/G/G] composite laminates. Meanwhile, the water absorption and diffusion coefficient of [G/P/G] composite laminates were 66.64% and 40.71% lower than non‐hybrid [P/P/P] composite laminates. Based on the findings obtained, it is anticipated that the hybridization of pineapple leaf and glass fibers endows the composite laminates with lightweight characteristic, remarkable mechanical properties and low moisture uptake sensitivity while improving the environmental friendliness of the materials. Therefore, hybrid composites have indeed attested a very high potential to be used in transportation sectors. [ABSTRACT FROM AUTHOR]

Jute and banana fibers are biodegradable green fibers being increasingly used to replace synthetic fibers in fiber‐reinforced polymer composites. Integration of jute and banana distinct natural fibers has the potential to improve composite performance in secondary structural applications. In this study, an equal quantity of unidirectional jute and banana fibers with four different fiber orientations [(0/0)3s, (0/45)3s, (0/90)3s, and (+45/−45)3s] was embedded in phenol formaldehyde resin to make hybrid laminates using the hot press method. Tensile, flexural, impact, interlaminar shear strength (ILSS), and single‐end notch bend tests are performed in accordance with the ASTM standards to evaluate the effect of fiber orientation on natural fiber hybrid composites (NFHCs). Experimental results revealed that changing the fiber orientations [(0/0)3s] leads to a major impact on reducing the mechanical properties of NFHC laminates to the extent of 39%. Furthermore, the tensile strength, Young's modulus, impact and ILSSs, and fracture toughness were found to be 37% higher for the (0°/0°)3s composite. Additionally, tensile, flexural, and impact fractured specimens were examined by scanning electron microscopy to understand the fiber–matrix failure behavior due to inter‐ply orientation in NFHCs. [ABSTRACT FROM AUTHOR]

Special insulated wires beyond the conventional pure perfluoroalkoxy (PFA) polymers need to be developed to meet the increasing thermal management and mechanical performance requirements. Advanced PFA nanocomposites enhanced by inorganic fullerene tungsten sulfide (IF‐WS2) nanoparticles have been fabricated by melt blending and hot press processes. Benchmarked against the PFA, the presence of IF‐WS2 nanoparticles in the composites resulted in a maximum tensile strength of 21.35 MPa and a maximum elongation at break of 275%, which are 66% and 149% higher than those of pure PFA, respectively. The nanocomposites with 0.5 wt% IF‐WS2 achieved a 17.5% increase in storage modulus, 26.8°C increase in the onset melt temperature, while 1 wt% IF‐WS2 increased the glass transition temperature (Tg) by 3.4°C and the crystallinity (χc) by up to 34.4%. And when the additional amount of IF‐WS2 nanomaterials is 0.25%, the best combination of performance is obtained. [ABSTRACT FROM AUTHOR]

Nanofibers offer great potential for improving the mechanical performance of optically transparent composites without compromising transparency. To achieve this, the reinforcing nanofibers must be thinner than the low end of the visible light spectrum (400 nm). Herein, a self‐mixing co‐electrospinning approach was employed to prepare electrospun meshes of well‐blended nylon‐6 (PA‐6) nanofibers and poly(methyl methacrylate) (PMMA) fibers, from which composite films containing PA‐6 nanofibers with varied diameters (approximately 100–800 nm) and mass fractions (1–7 wt%) were fabricated by hot‐press molding. When the PA‐6 nanofiber content was less than 5 wt%, the mechanical properties of the PA‐6/PMMA composite remarkably improved compared to those of neat PMMA, without considerably influencing its transparency. Furthermore, the thermal stability of the PA‐6/PMMA composite was clearly improved compared to that of neat PMMA. These results suggest that this material has the potential for wider adoption in applications requiring both transparency and high mechanical properties. [ABSTRACT FROM AUTHOR]

The effect of nanosilica content (0, 0.5, and 2 wt%) on mechanical performance of carbon fabric woven cloth reinforced polymerized poly(butylene terephthalate) resin composites (CF/pCBT) is investigated. The catalyst and nanosilica particles are added on the prepreg surface, and hot-press processing is adopted in order to manufacture CF/pCBT composites. The experimental results reveal that nanosilica could enhance the mechanical performance of CF/pCBT composites. After adding nanosilica in the composites, elastic modulus enhances 23.96%, and Mode-II fracture toughness increases 380.43%. Scanning electron microscope observation shows that dispersity of nanoparticles in composites plays an important role on the overall mechanical performance of the obtained composites. Furthermore, failure mechanism has been analyzed according to the damage morphology. POLYM. COMPOS., 38:2528-2535, 2017. © 2015 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Compression molding of randomly oriented strands (ROS) of thermoplastic composite is a new process that enabled the formation of complex shapes with high fiber volume fraction. During compression molding of ROS, several deformation mechanisms occurred. This article focused on the macroscopic squeeze flow mechanism. It ruled how the material will flow and fill intricate features of the mold. The squeeze flow behavior under large strain was investigated for Unidirectional (UD) and ROS. An experimental characterization was performed using an instrumented hot press. Also, to predict the associated thickness reduction, existing models using equivalent viscosity and lubrication assumptions were used. The results showed that large deformation of UD and ROS composite materials is mainly governed by two regimes: a Non-Newtonian fluid behavior at low strain followed by a yielded phase at large strain. Quantitative indicators were defined to analyze these two phases. They showed that current models available in the literature fail to predict accurately the squeeze flow of thermoplastic composites under high strain (>50%). Also, strands size (especially strand length) has a large effect on the squeeze flow mechanism. This article provided basic process window guidelines in terms of minimum pressure and achievable strain for compression molding of ROS parts. POLYM. COMPOS., 38:1828-1837, 2017. © 2015 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Poly(vinylidene fluoride)‐Graphene Oxide composite films were prepared by solution casting followed by hot press technique with variation of Graphene Oxide content up to 1.6 vol%. High Resolution Scanning Electron Microscope and Raman spectroscopy were used to investigate the morphology and the dispersion of GO. X‐ray diffraction (XRD) and Fourier transform infrared spectra were analyzed to identify and estimate the fraction of β phase. All the composite film samples are found to have fraction of β phase >80%. Dielectric constant of the composite films increases with increase in Graphene Oxide content up to 0.15 vol% and with further increment; it causes decrease in dielectric constant. Both dielectric loss tangent and ac conductivity show increasing trend with increment of Graphene Oxide content. Both remnant polarization and energy density are affected by Graphene Oxide loading. Remnant polarization increases with Graphene Oxide content whereas energy density follows the same variation trend that of dielectric constant. [ABSTRACT FROM AUTHOR]

To shorten the preparation cycle of Al/PEEK/CFRP laminates fabricated by Al sheets, peek films, and CFRP prepreg and reduce energy consumption during the preparation process to ensure the highest quality laminates, a novel forming process based on self‐resistance electric (SRE) heating was proposed. Considering the tensile properties, fracture morphology, and void content comprehensively, the influence of current intensity (11.5, 12.5, 13.5 A) on the forming quality of laminates was explored. This optimized electric heating process was compared with the traditional heating process with respect to forming time, energy consumption, and the performance of the prepared samples. The results show that when the current is 12.5 A, the molding quality of the samples prepared by the SRE process is better than that of the traditional process. In addition, the SRE process significantly reduces forming times and saves energy. This SRE heating method provides a new process optimization pathway for the preparation and formation of fiber metal laminates and exhibits great prospects for future research. [ABSTRACT FROM AUTHOR]

Natural fiber‐based polymer composites have been widely studied to substitute synthetic materials. In this research, pineapple leaf fibers (PALF) and coir fibers (CF) were loaded into a polylactic acid (PLA) matrix to develop composite materials with improved mechanical and thermal properties, which could be potentially applied as biodegradable food packaging. Biocomposites with different fiber ratios were manufactured using an internal mixer plasticizer and a hot press machine. Mechanical and thermal analyses of the obtained composites were carried out and the results were compared with those of pure PLA. Scanning electron microscopy (SEM) was used to observe the microstructural failure of the composites. Mechanical tests indicated that all the composites had higher tensile and flexural modulus, compared to those of neat PLA. Also, strength values were increased upon addition of PALF, while impact tests showed enhanced strength results upon addition of CF. SEM findings confirmed the outcomes of the mechanical tests. DMA results confirmed that the storage and loss moduli of the CF/PALF/PLA hybrid composites increased with respect to those of the neat PLA, whereas the tan δ decreased. The coefficient of thermal expansion (CTE) of the PLA composites decreased with the addition of fiber reinforcements. Based on the results achieved in this investigation, the hybrid composite containing CF and PALF in a 1:1 ratio (C1P1) presented the optimum set of mechanical properties and improved thermal stability, which make it suitable for applications such as food packaging and structure components to help reduce the environmental loads. POLYM. COMPOS., 40:2000–2011, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Short wood fibers (SWF) and a water based and formaldehyde free cross linking acrylate resin have been used to produce bulk biocomposites, as a possible material for automotive and friction applications. SWFs of 200–400 µm in length were mixed with the resin in various proportions (40–60 wt%) using a kneading device. The mixture was dried in an oven and later cured in a hot press. Two curing cycles were used for this study: (a) curing at a temperature of 150°C and a pressure of 70 bar and (b) curing at 170°C and a pressure of 80 bar. Various morphological features, flexural and thermal properties, density, and specific wear rate under sliding against smooth steel were examined. Results show that increase in fiber weight fraction led to increase in tensile strength when the material was processed with 170°C and a pressure of 80 bar. Composites with 60 wt% SWF processed with 170°C and a pressure of 80 bar exhibited the highest flexural strength (64 MPa) and flexural modulus (7.2 GPa). Composites processed at lower temperature and pressure (150°C and 70 bar) are found to possess inferior mechanical properties compared with those processed at higher temperature and pressure (170°C and 80 bar). This composite also possessed a nearly stable storage modulus up to 50°C. All composites showed specific wear rate between 10−5 and 10−6 mm3/(Nm) and a very high friction coefficient of μ = 1.25 against smooth steel surfaces. SEM images revealed that there is a very good interfacial adhesion between the fibers and the matrix. POLYM. COMPOS., 40:91–98, 2019. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Continuous basalt fiber (BF) reinforced epoxy matrix composites with different contents of micro‐tungsten powder were fabricated by hot‐press process with prospective of combined radiation shielding and mechanical functions. Gamma photon shielding and mechanical properties of the composites were evaluated. The measured mass attenuation coefficient shows that tungsten filler significantly improves the radiation shielding property of BF composite, especially for low and moderate photon energies of 80 and 356 keV. Flexural strength of BF composite decreases along with increasing tungsten concentration, while flexural modulus and interlaminar shear strength are not obviously affected by tungsten content. Given the advantages of lightweight, high mechanical property and good radiation shielding performance, the studied BF/tungsten composite is promising material with integrated shielding and structural properties for use in nuclear industry. POLYM. COMPOS., 39:E2106–E2115, 2018. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Sisal fiber (SF) and waterborne polyurethane adhesive were used to prepare SF‐based sound absorption material through hot press molding. SF with elastic polyethylene (PE) film interlayers was also fabricated as a new type of sound absorbing composite. The effects of SF treatment methods and PE film on sound absorption coefficient were evaluated. The alkaline‐treated SF composite had higher sound absorption as compared with the untreated SF composite when the sound wave was below 5500 Hz. The sound absorption peak of alkaline/oxidation‐treated SF composite moved towards low‐ and middle‐frequency regions. The SF/PE film composite showed that at low‐frequency the more layers of PE film inserted the better sound absorption property. The mass‐temperature relationship and FTIR of the composites were discussed. The SF surface and the cross section of the composites were observed by SEM, which showed the void structure and microfiber contributed to enhancing sound absorbing property. POLYM. COMPOS., 39:2812–2818, 2018. © 2016 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

In the presented study, lithium chloride (LiCl) was used as a modifier to reduce the melting point of polyamide 6 (PA6) and low melting point PA6/wood fiber composites (LPA6/WFC) were prepared with a hot‐press machine. Non‐isothermal crystallization analysis revealed that as little as 3 wt% LiCl decreased the crystallinity of LPA6/WFC from 21.43% to approximately 10% and reduced the melting point of composites from above 220°C to below 200°C, hence the composites can be produced industrially as well as severe degradation of wood fibers can be avoided. Both LiCl and wood fibers increased the glass transition temperature (Tg) of LPA6/WFC, and the Tg of the composites can reach up to 83.2°C, indicating that composites subjected to high temperature circumstances can still retain good dimensional stability and rigidity. In addition, the composites exhibited good mechanical properties, revealed by a flexural strength of the composites of up to 92 MPa. POLYM. COMPOS., 39:E1574–E1580, 2018. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Advanced sandwich structures have emerged as new multifunctional structures with low density and good mechanical performance. Sandwich composites have high strength to weight and high stiffness to weight ratio. Good thermal and sound insulation can be provided using sandwich composite materials. Sandwich composites have high energy absorbing capacity. Multifunctional sandwich composites exhibit mechanical performance and other functional properties such as energy storage, electrical conductivity, etc. Further, the core can be used for routing wires, foam filling, fluid storage, embedding bars, etc. Thus, the multifunctionality can be introduced to the resuting composite materials. This article reviews current research on innovative sandwich structures with integrally woven corrugated core, honeycomb, foam, and 3D printed core architectures, emphasizing their multifunctionality. Aspects of sandwich structure with types of face and core structure design, material design, mechanical properties, and panel performance and damage, including multifunctional benefits, are reviewed. Examples of engineering and modern uses of sandwich structures are presented, covering hypersonic vehicles, civil and marine engineering, electronics, and biological fields. A list of areas for future study initiatives is also included. This review will serve as a baseline for future studies to do more research in the same direction. Highlights: A detailed review of various types of core materials and sandwich structures is presented.Sandwich structures have high energy absorbing capacity.3D woven sandwich structures, their manufacturing and failure mechanics is discussed.Modern applications of sandwich structures are detailed. [ABSTRACT FROM AUTHOR]

The polyimide (PI) fabric/epoxy (EP) composites modified with different content of micro-SiO2 hollow spheres were prepared by dip-coating and subsequently hot-press process. For comparison, the pure EP and the unmodified PI fabric/EP composite were also fabricated. The differential scanning calorimetry was conducted to investigate the crosslinking reaction of composites. The results indicated that there exhibited a remarkable improvement in the mechanical and tribological properties of PI fabric/EP composites after incorporating the micro-SiO2. The best tribological properties were obtained when the content of micro- SiO2 was 2 wt%, whose wear rate was 71.9% lower than that of unmodified PI fabric/EP composite. The worn surfaces were observed by a scanning electron microscope to illustrate the friction mechanisms. Note that the skeleton network structure of fabric throughout the whole composites supported the matrix. At the same time, the microparticulates filled in the interstices of fabrics interwoven structure and the gaps between layers of fabrics, which propped up the skeleton network of fabric under the high frictional load and afford excellent interface between fabrics and EP. This ensures the outstanding tribological properties of PI fabric/EP composites. [ABSTRACT FROM AUTHOR]

Epoxy resin was modified by adding a silane coupling agent/nano-calcium carbonate master batch. Then, samples of binary carbon fiber/epoxy composites and ternary fiber/nano-CaCO3/epoxy were prepared by hot press process. The interlaminar shear strength (ILSS) of the carbon fiber/epoxy composites was investigated and the results indicate that introduction of the treated nano-CaCO3 enhances ILSS obviously. In particular, the addition of 4 wt% nano-CaCO3 leads to 36.6% increase in the ILSS for the composite. The fracture surfaces of the carbon fiber/epoxy composites and the mechanical properties of epoxy resin cast are examined and both of them are employed to explain the change of ILSS. The results show that the change of ILSS is primarily due to an increase of the epoxy matrix strength and an increase of the fiber/epoxy interface. The bifurcation of propagating cracks, stress transfer, and cavitation are deduced for the reasons of strengthening and toughening effect of nano-CaCO3 particles. POLYM. COMPOS., 38:2035-2042, 2017. © 2015 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]