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Highlights In this study, the impact performance of carbon fiber‐reinforced polymer (CFRP) composites under low‐speed impact conditions was investigated using a data‐driven approach. Both material properties and impact parameters were determined through experimental methods and finite element (FE) analysis. FE analysis was conducted on CFRP composite structures to generate impact force and absorbed energy datasets. Various impact conditions, such as impactor height (0.5–1.25 m), impactor shape (flat, truncated cone, bullet, and cone), and composite plate thickness (1–4 mm), were incorporated into an artificial neural network (ANN) model to predict the impact behavior of CFRP composites. Using the optimal plate thickness identified from the data‐driven model, CFRP plates were fabricated using vacuum‐assisted resin transfer molding and tested under different impactor shapes and heights using drop impactors. The FE analysis revealed that increasing the impactor height improved the impact force by 37.8% and the absorbed energy by 178%. The impactor shape also significantly influenced the results, with a flat‐to‐cone‐shaped impactor increasing the impact force and absorbed energy by 167.2% and 440%, respectively. Additionally, the plate thickness analysis showed that a 2 mm plate provided optimal impact force and absorbed energy, with values of 1.09 kN and 8.12 J, respectively. The prediction of the force and energy experienced by CFRP material under different impact conditions was validated using root mean squared error (RMSE), mean square error (MSE), mean absolute error (MAE), and R2 metrics. The model demonstrated excellent performance with the lowest RMSE (0.0118), MSE (0.0003), and MAE (0.0096), indicating that the predicted impact forces closely matched the actual forces. The highest R2 value (0.9999) suggests that the model accurately captures the variance in impact force across varied impact conditions. Similarly, R2 values close to one indicate that the model effectively explains the variability in energy absorption, making it highly reliable. The ANN model also showed that predictions for absorbed energy were more accurate than those for impact force under varying impact conditions. Furthermore, the predicted impact force and absorbed energy from the FE analysis and ANN model closely aligned with the experimental results. Damage morphology observations indicated matrix cracking at higher impact velocities, with more significant penetration occurring with cone‐shaped impactors. These findings demonstrate a strong correlation between experimental and numerical outcomes, validating the effectiveness of this combined approach for evaluating the impact resistance of CFRP composites. The impact performance of CFRP composites under different impact conditions was modeled. An Artificial Neural Network model was developed to predict impact performance. The VARTM method was adopted for the development of optimized CFRP composites. Impactor height and shape were found to be the most influential factors Impact damage areas were related based on impactor height and shape. [ABSTRACT FROM AUTHOR]

In selective laser etching for the interfacial strengthening of Fiber Metal Laminates (FMLs), the wettability of customized structured features significantly affects their overall mechanical properties. For two-level features, their complicated geometry makes the evaluation of wettability difficult, which introduces challenges to feature design. In this study, a sandwich FMLs comprising an AA2024-O metal skin and a plain-woven carbon-fiber fabric core is investigated. Three types of two-level feature interfaces are designed and introduced into the FMLs structure. To understand the effect of two-level features on the resin flow and dynamic wetting progress in resin transfer molding, two-phase flow Computational Fluid Dynamics numerical models coupled with porous media and level-set numerical methods are built. The feasibility of the numerical simulation in the qualitative analysis was verified by comparing the results with those of the testing porosity values from X-ray scanning. In addition, the mechanisms of pore formation and transportation are revealed. These results indicate that the deeper groove structure in the etched features plays an important role in discharging residual air and determining the transformation of pores to reduce porosity. The permeability orientations of the porous media and surface structure both have significant impacts on the flow behavior and formation of pores. [ABSTRACT FROM AUTHOR]

The utilization of bio-based materials for the manufacturing of fiber-reinforced polymer composites is gaining importance under the sustainability paradigm. The identification of suitable process parameters and limited process reproducibility remain among the major challenges to enhance the industrial application potential of bio-based composites. This is especially relevant, as the manufacturing process influences composite quality, economic performance and environmental impacts. This study compares Resin Transfer Molding and Vacuum Assisted Resin Infusion for two sets of process parameters in order to manufacture a composite plate consisting of a flax-fiber textile impregnated with a partially bio-based epoxy matrix. Process quality is described through statistical analysis of processing and composite properties, and performance in terms of process replicability and reliability using performance estimates. Processing parameters were selected to depict a range of manufacturing scenarios that were suitable for the selected bio-based material system from curing for 180 min at 60 °C to curing for 30 min at 100 °C. For an identical set of process conditions, Resin Transfer Molding outperforms Vacuum Assisted Resin Infusion in terms of tensile and flexural characteristics. Conversely, the latter shows the strongest fiber-matrix adhesion and the most homogeneous impregnation. Whereas manufacturing at lower temperature leads to positive effects on composite quality, higher processing temperature with shorter curing cycles achieve highest process performance in terms of Pp and Ppk indices. An additional annealing at 120 °C neither increases composite quality nor reduces manufacturing-induced variability. Results depend on processing differences and indicators to determine process performance, as well as methodological choices. [ABSTRACT FROM AUTHOR]

Highlights In the present paper, we manufactured carbon fiber‐reinforced polyamide‐6 composite (CF‐PA6) by resin transfer molding and compared their impact performance with an equivalent automotive grade epoxy‐matrix composite (CF‐Epoxy). Such comparison is pertinent as the new thermoplastic composite will compete with the traditional thermosetting composite, so impact characterization carried out at the same conditions is necessary for evaluating the possibilities of the new material. The energy dissipation capacity of the CF‐PA6 was 27% higher, the maximum impact‐peak load was 5% smaller, and the damage threshold was similar for both composites. Regarding residual post‐impact properties of samples damaged by a 25 J impact energy, CF‐PA6 retained 62% of its stiffness, 84% of its strength and 67% of its energy dissipation capacity. In contrast, CF‐Epoxy retained 46%, 44% and 40% respectively. Comparison of impact behavior between CF‐PA6 (RTM) and CF‐Epoxy (RTM). The damage thresholds of both composites were similar (~2.5 J). The penetration and perforation thresholds of CF‐PA6 were 48% and 27% higher. Post‐impact residual property: CF‐PA6 retained 60% of its stiffness. [ABSTRACT FROM AUTHOR]

Highlights With the advent of the 5G era, electromagnetic pollution has been increasingly serious. Structural electromagnetic wave (EW) absorbing composites play a key role in both civil and military applications. However, the laminated plate structure and laminated honeycomb structure EW‐absorbing composites were prone to delamination and low EW absorbing performance. To enhance the EW absorption and mechanical properties of composite materials, this study successfully developed a novel three‐dimensional hexagonal honeycomb woven composites (3D‐HHWC). 3D‐HHWC with a three‐dimensional hexagonal honeycomb woven fabric (3D‐HHWF) as the reinforced materials was manufactured by the vacuum‐assisted resin transfer molding (VARTM) process with epoxy resin, carbon black (CB), multi‐walled carbon nanotubes (MWCNTs), and carbonyl iron powder (CIP) as functional materials. The EW absorption performance and bending mechanical properties of 3D‐HHWC with different structural parameters were compared and analyzed. The test results demonstrated that the 3D‐HHWC (H2‐3) achieved a remarkable minimum reflection loss of −38.1 dB with the effective electromagnetic absorption band (EAB) 13.8 GHz. Additionally, CST provided a clear explanation of the electromagnetic field distribution elucidating the mechanism for EW absorption. While the 3D‐HHWC (H2‐3) had a maximum bending load 6603.9 N without obvious delamination phenomenon. Furthermore, finite element simulation clarified internal stress distribution explaining the failure mechanisms. In conclusion, the 3D‐HHWC exhibited outstanding EW absorption and mechanical properties for widespread application in military and aerospace fields. The 3D‐HHWC was formed by VARTM process with epoxy resin, CB, MWCNTs, and CIP. The 3D‐HHWC had excellent EM performance with RLmin −38.1 dB and EAB 13.8 GHz. CST provided a clear explanation of the electromagnetic field distribution. The 3D‐HHWC had a maximum bending load 6603.9 N without obvious delamination. FEM clarified internal stress distribution to explain the failure mechanisms. [ABSTRACT FROM AUTHOR]

Highlights Basalt fibers (BF) are widely used in shipbuilding due to their excellent corrosion resistance. However, basalt fibers do not possess good electromagnetic wave absorption properties, failing to meet the stealth performance requirements of ships. Therefore, this study focuses on basalt fiber composite materials, modifying the matrix by adding different amounts of carbon nanotubes (CNTs). Carbon nanotube‐basalt fiber‐epoxy resin absorptive composite materials are prepared using Vacuum Assisted Resin Transfer Molding (VARTM) technique to investigate the influence of CNT content on the materials. Samples with added CNTs can effectively absorb electromagnetic waves in the low‐frequency range, reducing surface reflectivity. In the high‐frequency range, the impedance matching value of the samples initially increases slowly. When the CNT content reaches 1.5 wt%, at a thickness of 2.5 mm and a frequency of 9.6 GHz, the minimum reflection loss of the sample is −14.40 dB, with an effective absorption bandwidth of 0.7 GHz. Also, CNTs can enhance the mechanical properties of composite materials. With increasing CNT content, both the bending strength and tensile strength of the composite materials are improved. When the CNT content reaches 1.5 wt%, the average tensile fracture strength of the material increases by 21%, and the bending strength increases by 9%. Enhanced low‐frequency electromagnetic wave absorption from CNTs and reduced polarization. Improved impedance matching and attenuation at high frequencies with CNTs. Significant enhancement in flexural and tensile strength due to CNTs and basalt fibers. [ABSTRACT FROM AUTHOR]

This research work aims to investigate the effect of fabrication techniques on the physico‐mechanical properties of pistachio shell (PS) filled glass‐epoxy composites and to compare the experimental findings with numerical simulation results using finite element analysis (FEM). These hybrid composites are fabricated by vacuum‐assisted resin transfer molding (VARTM) and hand layup (HL) techniques with fixed glass fiber fraction (20 wt. %) but different PS powder loadings of 0–30 wt. %. The composites are then characterized for physical, compositional, micro‐structural and mechanical properties. The micro‐structural analysis of the filler and composites is performed using electron microscopy and stereo‐microscopy. To identify the phases present in both the raw filler and the composite, an x‐ray diffraction test is performed. The presence of functional groups is identified with the help of Fourier transform infrared spectroscopy (FTIR). It is observed that there is a reasonable improvement in the mechanical properties of the composites with increase in PS powder content, irrespective of the fabrication process used. The density and void fraction are also greatly affected by the amount of filler particles present in the composites and also on the composite fabrication technique. The FEM analysis is also carried out using ANSYS 22.0 workbench to determine the characteristic properties numerically. The comparison of experimental and numerical results yields that the properties obtained by using VARTM results are close to experimental ones with errors lying in the range of 1%–4%. These composites can possibly find potential applications in light duty structures and wear resistant applications. Highlights: Development of hybrid composites using HL and VARTM techniques.Physical and mechanical properties alter with filler loading.Evaluation of mechanical properties using finite element analysis.Validating the model by comparing experimental and numerical results. [ABSTRACT FROM AUTHOR]

Carbon fiber‐reinforced composite materials exhibit excellent mechanical and electromagnetic shielding capabilities. However, they have some drawbacks, such as high cost and significant reflection losses. In order to address these shortcomings, this study set out to design a sandwich‐structured composite material and produce a composite material designed for electromagnetic shielding using Vacuum Assisted Resin Transfer Molding (VARTM) technology. This composite material promotes the "absorption‐reflection‐reabsorption" process of electromagnetic waves, significantly enhancing its shielding effectiveness, achieving up to 59.4 dB of shielding effect in the 8.2–12.4 GHz (X‐band) range. The study also employed carbon nanotubes (CNTs) matrix doping to modify the composite material, significantly reducing reflection losses. When the amount of carbon nanotubes added reaches 0.6 wt%, the overall SE can be increased by 18%. Additionally, the introduction of CNTs significantly improves the flexural strength and tensile strength of the composite material; at a 0.6 wt% CNT content, the average tensile strength increased from 526.4 to 600.9 MPa, indicating good interfacial interactions between CNTs and epoxy resin. This work provides valuable insights for the preparation of high‐performance electromagnetic shielding materials, with profound theoretical and practical significance. Highlights: Observations through SEM and CT scanning techniques reveal that Vacuum Assisted Resin Transfer Molding (VARTM) technology facilitates strong interlayer bonding between carbon fibers, glass fibers, and copper wires, alongside effective epoxy resin adhesion, thus enhancing the mechanical properties.The sandwich structure's impedance mismatch characteristic facilitates an efficient "absorption‐reflection‐reabsorption" process of electromagnetic waves. Additionally, the incorporation of Carbon Nanotubes (CNTs) enhances the absorption mechanism, reducing reflection losses.Incorporating CNTs further boosts both flexural and tensile strengths, attributed to improved interfacial interactions inhibiting crack formation. [ABSTRACT FROM AUTHOR]

Highlights A detailed investigation was employed on the manufacturing process of Glass Fiber (GF) reinforced poly‐L‐lactide (PLLA) composites (GFRP) during in‐situ PLLA polymerization using Resin Transfer Molding (RTM). The lower viscosity of lactide, in comparison to PLLA, led to a strong interaction between PLLA and GF as a result of improved penetration into the fiber matrix, resulting in a high conversion rate of 100% for GFRP and 91.9% for PLLA. GF incorporation into the composite material resulted in an improved crystallinity of 55.65% for GFRP, where PLLA showed crystallinity of 36.5%. A GFRP composite with exceptional mechanical properties, including 122.3 MPa tensile strength and 4.485 GPa modulus, was achieved. Both surface and bulk erosion were seen during the breakdown of these composites. These composites seem to be a viable substitute for metallic implants in biological applications. In situ, resin transfer molding of poly‐l‐lactide and GF composite. Higher volume fraction such as 40% w/v loading of GF into composites. 1% conversion of GFRP is achieved. GFRP shows the machinal strength of 122 MPa and harness of 4.2 GPa. Biocompatibility of GFRP composites in body stimulated conditions. [ABSTRACT FROM AUTHOR]

The automobile industry is exploring the use of HP-RTM (high-pressure resin transfer molding) for mass-producing glass fiber-reinforced plastic (GFRP) chassis parts to achieve weight reduction. In this process, dry fabric is used as a material. However, the fatigue endurance performance of these parts deteriorates due to the bobbin threads in the dry fabric. This study aims to propose a laminating method to prevent the deterioration of the durability of GFRP chassis parts with bobbin threads. Specimens were fabricated with different fiber volume fractions (Vf) and bobbin thread positions. After manufacturing, static properties were evaluated to compare the physical properties of each specimen, and the stress for fatigue durability evaluation was determined based on these static properties. Finally, fatigue endurance performance evaluations were conducted to determine the optimal lamination conditions for GFRP chassis parts. The results showed that for the three laminating methods applied in this study, an increase in Vf not only enhanced the static properties but also reduced waviness, as confirmed through OM images and changes in the slope of the stress–strain curve. Additionally, fatigue endurance tests revealed that, along with the improvement in waviness, adjusting the position of the bobbin threads—which negatively impact durability—resulted in an increase in fatigue endurance performance from approximately 67,000 cycles to about 870,000 cycles, an improvement of approximately twelve times. [ABSTRACT FROM AUTHOR]

Development of biocomposites is becoming a necessity due to environmental concerns. Polylactide is a matrix of choice, regarding its bio‐sourced and compostable nature along with its mechanical properties. In this study, poly(L‐lactide)/flax biocomposites were produced using thermoplastic resin transfer molding (TP‐RTM) in one step process from the monomer, affording sustainable and fully compostable composite materials. The polymerization of L‐lactide (L‐LA) monomer was promoted by tin octoate, affording poly(L‐lactide) (PLLA) matrices displaying monomer conversions superior to 96% and mass‐average molar masses above 140,000 g/mol. Flax fibers were used as received without any functionalization which is usually conducted to prevent the hydroxyl groups to conduct side reactions. Mechanical testing revealed bending modulus of 9.3 GPa and bending strength of 177 MPa comparable to existing literature values for PLLA/flax composites produced by other techniques. Digital microscopy analysis provided insights into impregnation quality and void characterization within the composites. In addition, the durability of these biocomposites was also evaluated via accelerated aging tests. Highlights: PLLA/flax biocomposites were produced by TP‐RTM for the first time.In situ polymerization of the PLLA matrix associated with non‐functionalized flax fabrics was conducted.Bending properties were found in line with those of PLLA/flax composites produced by compression molding.Aging tests under UV at 50°C of PLLA/flax biocomposites were conducted. [ABSTRACT FROM AUTHOR]

This study investigated the manufacturing processes for structural supercapacitors (SSCs) using smear molding (RS), resin transfer molding (RTM), and vacuum-assisted resin transfer molding (VARTM). Woven carbon fibers were used as the electrode, woven glass fibers as an insulating layer, and an alkaline/epoxy compound as the electrolyte. In the RTM process, due to the vacuum and the high-pressure injection of the electrolyte, the electrochemical and mechanical properties of the SSC can be greatly improved, and the void contents in the SSC can be reduced. The balanced electrochemical performance and mechanical properties of SSCs were observed in the range of epoxy content from 15 wt% to 30 wt%. This study contributes to the development of SSCs through the establishment of the fabrication process for improvements in part quality. The fabrication method demonstrated here can be directly applied by industries to produce even larger-scale SSCs, opening up new possibilities for practical implementation and scalability. [ABSTRACT FROM AUTHOR]

Natural fiber‐reinforced composites have emerged as a promising alternative in various industries, including automotive, aerospace, construction, and civil engineering, owing to their eco‐friendly nature and favorable mechanical properties. However, challenges such as low thermal stability and high moisture absorption limit their widespread use. To overcome these limitations, surface modifications such as mercerization, benzoylation, silane treatment, and acetylation have been extensively explored. Hybrid composites (HCs), combining natural and synthetic fibers, offer a compelling solution by harnessing the unique properties of both materials. This review comprehensively examines the types of fibers and polymers utilized in HCs, along with various chemical treatments to enhance their properties. Additionally, a detailed analysis of different manufacturing processes for HCs is provided, including hand lay‐up, vacuum‐assisted resin transfer molding, autoclave molding, injection molding, and compression molding. Furthermore, this review highlights recent advancements in HCs and their applications. Significant outcomes include a deeper understanding of the synergistic effects between natural and synthetic fibers, improved mechanical and thermal properties, and enhanced applications in diverse industries. The potential of HCs as a sustainable and high‐performance material solution emphasizes the importance of ongoing research and innovation in this field to overcome existing challenges and unlock new possibilities for composite engineering. Highlights: Surface modifications such as mercerization, benzoylation, and silane treatment enhance the properties of natural fibers in composite materials.Hybrid composites (HCs) offer unique advantages by combining natural and synthetic fibers, including improved thermal, mechanical, and damping properties.Various chemical treatments and manufacturing processes contribute to enhancing the properties and applications of HCs.Recent advancements in HCs have led to an improved understanding and utilization of composite engineering across multiple industries.The review discusses challenges, opportunities, and future prospects for HCs, emphasizing the need for ongoing research and innovation in this field. [ABSTRACT FROM AUTHOR]

Composite materials play a crucial role in various industries, with plastic composites being particularly significant. This research specifically focuses on producing cotton fabric layers to reinforce polymeric composites. The experiment is designed in two phases. In the first stage, woven fabric is produced using roving as weft insertion instead of the conventional threads or spun yarns. This modification enhances the absorbency of the resin matrix during composite production, leading to improved properties. The second stage of the experiment involves manufacturing composite materials using different fabric structures (plain, twill, and sateen) and varying numbers of fabric layers (1, 3, and 5). This is achieved through a novel process called Vacuum Assisted Resin Transfer Molding (VARTM), which is used for fabric composites instead of the traditional laminated composites. VARTM offers advantages in terms of production efficiency and composite quality. To evaluate the physical and mechanical properties of the resulting composites, several tests are conducted. These include tensile properties testing, bending rigidity testing, measurement of composite thickness, and determination of density. The test results provide valuable insights into the performance of fabric composites under different conditions. Furthermore, the experimental results are compared with simulations conducted using the Finite Element Method (FEM) through COMSOL software. The agreement between the experimental and simulated results confirms the reliability of the proposed approach. [ABSTRACT FROM AUTHOR]

The influence of hygrothermal aging on the mechanical properties of flax fiber‐reinforced polymer (FFRP) composites was studied by examining the mechanical properties and failure mechanism of the composite laminates exposed in distilled water at different temperatures. The resin transfer molding (RTM) process was used to manufacture FFRP laminates, which were then subjected to accelerated aging tests in distilled water at different temperatures. The moisture absorption characteristics of FFRP were analyzed by a water absorption test. Tensile, bending, and low‐velocity impact tests of laminates after different aging conditions were performed. Combined with DSC and FTIR tests, the failure mechanism of FFRP exposure to hygrothermal aging was analyzed. The result indicated that the increase in temperature will accelerate the moisture absorption process of FFRP, and the hygroscopic behaviors at different temperatures conform to Fick's law. In the early stage of hygrothermal aging, the composites undergo post‐curing, and the tensile and bending strengths increase. After that, the tensile and bending strengths are decreased because of the thermo‐oxygen aging of materials and fiber/matrix interface damage. After hygrothermal aging, the impact peak force of FFRP decreases obviously while the absorbed energy increases due to the increase of internal defects and plasticization of composites. The increase of hygrothermal aging temperature aggravates the aging of materials, resulting in a more obvious decline in the tensile, bending, and impact properties of the composites. Highlights: The effect of hygrothermal aging on the mechanical properties of FFRP is investigated.With the increase of hygrothermal aging time, the tensile and bending strength of FFRP increased at the early stage of aging and then decreased.After hygrothermal aging, the impact peak force of FFRP decreases and the absorbed energy increases due to the increase of internal defects and plasticization of composites. [ABSTRACT FROM AUTHOR]

Three‐dimensional graphene architecture (3DGA) as reinforcement with successive reinforcement effect has attracted intense attention in the field of polymer composites, while 3DGA also faces the disadvantages of weak interfacial adhesion with matrices. The surface decoration of 3DGA with molybdenum disulfide (3DGA@MoS2) further promoted the diffusion and penetration of epoxy molecular for 3DGA network with the aid of resin transfer molding (RTM) technic. The MoS2 transition nanolayer not only forms covalent bonding with 3DGA but mechanical interlocks with epoxy, which effectively improved the interface combination in composite. Compared with neat epoxy, the glass transition temperature (Tg) and tensile strength increased by 18°C and 58.6%, as well as the average friction coefficient and wear rate decreased by 84% and 89%, respectively, by low loading of only 2 wt% 3DGA@MoS2. Hence, the 3D graphene modified strategy by surface decoration provides a new insight for manufacturing high‐performance epoxy‐graphene composites with excellent tribological properties. Highlights: A highly ordered and interconnected 3DGA reinforcement was fabricated.MoS2 serves as interlayer, forming covalent bond and mechanical interlock.Incorporation of 3DGA@MoS2 enables rapid heat conduction and load transfer.Bi‐interpenetrating 3D structure/polymer network endows good wear resistance.Improved comprehensive properties ascribe to strong interface adhesion. [ABSTRACT FROM AUTHOR]

This paper proposes a complete model for simulating and controlling particle distribution in the final part manufactured by the resin transfer molding (RTM) process. This model combines (i) a numerical model to simulate the injection of a particle-filled resin through the fibrous medium and (ii) the integration of the genetic optimization algorithm to control the final particle distribution in the composite. Firstly, the numerical model is validated by comparing its numerical results with experimental measurements from the literature. Next, global sensitivity analysis methods were applied to identify the parameters (material and process) with the most significant influence on final particle distribution. As a result, it was found that the injected particle concentration is the most influential parameter compared to the injection pressure and the initial volume fraction of the preform, which has negligible effects. Finally, optimization applications were carried out to test the proposed approach's robustness. Four different and interesting profiles in the final distribution of particles in the composite were targeted: uniform distribution (UD) and functionally graded (FG) reinforcements (FG-O, FG-X, and FG-NI). The last three profiles are based on functionally graded materials (FGMs) with a substantial property gradient. In all cases, an optimal solution for the evolution of the initial concentration is reached, and the final particle distribution obtained after the injection simulation with this optimized initial concentration leads quite precisely to the desired profile. [ABSTRACT FROM AUTHOR]

Silicon‐containing arylacetylene resin (PSA)‐matrix composites hold great potential for aerospace applications due to their excellent heat resistance. In recent years, many PSAs with specific functions have been designed via materials genome approach (MGA), and appropriate resin transfer molding (RTM) curing processes need to be screened to strike a balance between low cost and high quality. In this study, a novel tool based on finite element curing simulation and multiobjective genetic algorithm was developed to optimize the RTM curing process for novel PSA‐matrix composites. The silicon‐containing fluorenylacetylene resin (PSA‐VBF) was selected as the object to systematically characterize its apparent curing kinetics. To address the problem of explosive polymerization of the resin at the injection port during the RTM process, a multiobjective optimization of the curing process using a genetic algorithm was performed to obtain the Pareto front with the maximum temperature gradient at the injection port of the resin, the maximum degree of cure gradient of the composites, and the process time as the objectives. A global sensitivity analysis was also conducted to identify the key parameters. The results demonstrate that the optimized curing process can significantly reduce the temperature gradient and the curing degree gradient with improved curing efficiency. [ABSTRACT FROM AUTHOR]

AbstractThe tensile properties and damage behaviors of prepreg-resin transfer molding (RTM) co-cured composite bolted T-joints, consisting of an internal skeleton and an external skin, were investigated through experimental and numerical methods. With the validated finite element model, the effects of adding load-carrying beams, the corner radius and the stacking sequence were investigated. Results indicate that the novel T-joint, weighing only 55.7% of an equivalent sized 2A12 aluminum T-joint, can achieve 82% of the aluminum T-joint’s tensile stiffness and 107% of its proportional limit load. Damage in the joint initiates near the bolt holes and leads to delamination failure within the skeleton. With load-carrying beams including bolt holes, the tensile stiffness and ultimate load increase to 1.11 and 1.51 times that of the original configuration, respectively, with the final failure mode shifting to the fracture of the base panel. With the final failure mode unchanged, the ultimate load remains essentially unchanged with increasing the corner radius. Under tensile loads, the preferred stacking sequence for the skeleton is [0/+45/90/−45]nS. For the skin, the greater the number of ±45° plies, the higher the ultimate load, while the greater the number of 90° plies, the higher the tensile stiffness. [ABSTRACT FROM AUTHOR]

This study evaluates multimodal imaging for characterizing microstructures in partially impregnated thermoplastic matrix composites made of woven glass fiber and polypropylene. The research quantifies the impregnation degree of fiber bundles within composite plates manufactured through a simplified compression resin transfer molding process. For comparison, a reference plate was produced using compression molding of film stacks. An original surface polishing procedure was introduced to minimize surface defects while polishing partially impregnated samples. Extended-field 2D imaging techniques, including polarized light, fluorescence, and scanning electron microscopies, were used to generate images of the same microstructure at fiber-scale resolutions throughout the plate. Post-processing workflows at the macro-scale involved stitching, rigid registration, and pixel classification of FM and SEM images. Meso-scale workflows focused on 0°-oriented fiber bundles extracted from extended-field images to conduct quantitative analyses of glass fiber and porosity area fractions. A one-way ANOVA analysis confirmed the reliability of the statistical data within the 95% confidence interval. Porosity quantification based on the conducted multimodal approach indicated the sensitivity of the impregnation degree according to the layer distance from the pool of melted polypropylene in the context of simplified-CRTM. The findings underscore the potential of multimodal imaging for quantitative analysis in composite material production. [ABSTRACT FROM AUTHOR]

A lightweight water-soluble core mold material for hollow shell composites was prepared by hot drying process with polyvinylpyrrolidone (PVP) aqueous solution as the adhesive and hollow glass microspheres as the matrix material. The effects of the content of adhesive and different treatment methods on the flexural strength, compressive strength and dissolution rate of the core mold were studied, and the microstructure of the core mold material was observed by scanning electron microscope. The results show that adhesive dosage of 40%, the flexural strength and compressive strength could reach up to 3.346 MPa and 3.499 MPa, with a water solubilization rate of 0.238 g/s. After the coupling agent treatment and high temperature treatment, the core mold strength and dissolution rate are improved, and the modification effect is good; small filler sizes can effectively fill the gap formed by matrix materials accumulation, improve the mechanical strength and affect the water solubility rate. The properties of water-soluble core can meet the requirements of resin transfer molding (RTM) and vacuum bag molding, which provides a solution for the integrated molding of profiled hollow profiles. [ABSTRACT FROM AUTHOR]

This paper reports the thermally activated ultralow friction of 100% cellulose nanofiber (CNF) molding. The mechanism of friction reduction was investigated using a laboratory-built in-situ Raman tribometer. Our experimental results showed that a CNF molding exhibited an ultralow friction coefficient of below 0.04 in a CNF ring and steel disk tribopair under high-temperature conditions (T > 100°C). The results of the temperature-rise friction test showed that the friction coefficient of the CNF molding strongly depended on the temperature and decreased linearly with increasing temperature. The in situ tribo-Raman monitoring results, during friction, indicated a change in the structure of the CNF molding. Therefore, the crystallinity indices and lengths of the CNF fibers gradually changed as the temperature increased. Moreover, transfer tribofilms were observed on the counter-steel surface against the CNF rings. When the CNF molding exhibited thermally activated ultralow friction, the tribofilm was mainly composed of cellulose and graphitic carbon. Our results suggest that the thermal and friction-activated structural transformations of CNF molding and CNFderived transfer film formation are pivotal factors contributing to the ultralow friction phenomenon observed in CNF molding at high temperatures. [ABSTRACT FROM AUTHOR]

For the first time in this paper, a composite sandwich panel with a novel circular-shaped core reinforced with silica nanoparticles (SNPs) is designed and fabricated using the vacuum-assisted resin transfer molding (VARTM) method. Carbon fibers and epoxy resin are utilized to construct the composite sandwich panels, followed by polyurethane foam injection. After fabrication, the sandwich panels undergo uniform compression testing to examine their mechanical behavior and properties. In this study, the effects of various parameters, such as core length, core height, weight percentage (wt.%) of SNPs, and polyurethane foam, on the compressive strength of the structure are evaluated. To validate the results, a finite element simulation of the sandwich panel compression test is performed using ABAQUS software, and the results obtained are compared with experimental data, showing good agreement. The results of this research demonstrate that adding SNPs within a specific range results in a considerable enhancement of the structural strength. Adding SNPs up to 3% leads to approximately a 19% increase in the compressive strength of the structure. However, adding 4 wt.% SNPs results in a decrease of about 12% in the strength of the sandwich panel. Additionally, the core's geometry significantly influences the control of compressive strength and rigidity of the sandwich panel. In other words, by increasing the core length, the compressive strength increases by 38%, while increasing the core height decreases compressive strength by about 30%. Also, it is found that adding polyurethane foam to the sandwich panel, despite a slight increase in weight, leads to a significant increase in compressive strength by about 32% and postpones its ultimate failure. Eventually, the hybrid specimen exhibits a strength approximately 57% greater than that of the pure foamless sandwich panel. [ABSTRACT FROM AUTHOR]

The objective of this research was to examine the bamboo fiber preforming procedures and the effects of preforming on the mechanical properties. The bamboo fibers were bent to an angular shape by using mold compression. Different moisture contents were applied to the bamboo fibers before bending. Next, tensile tests were conducted on the preformed bent fibers to investigate the strength degradation caused by fiber damage during the forming process. Additionally, the vacuum preforming method, limited to a pressure of 1 atm, was used for bamboo fiber bending preforming. Different fillet radii of the angled shapes were used in the experiments to investigate the impact of the angle curvature at the bending points on the strength of the bent bamboo fibers. Unidirectional bamboo fiber mats were manually woven using polyester fiber lines and preformed with a closed mold. The fabrication of the unidirectional bamboo fiber/epoxy resin composites was conducted by vacuum-assisted resin transfer molding (VARTM). In this study, valuable insights into the design of the bamboo fiber preforming and composite manufacturing processes are provided, and our results can be used to contribute to the progress and utilization of the bamboo fibers in composite materials. [ABSTRACT FROM AUTHOR]

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The use of hybrid reinforcement in polymer composites has been getting attention due to its potential for weight and cost reduction while achieving improved design flexibility for mechanical and thermal properties. In this study, an interply hybridization of epoxy laminates was performed using layers of solid and hollow glass fibers. The structural and thermal performance of the resulting hybrid vascular composites was investigated. All composite parts were manufactured using vacuum‐assisted resin transfer molding (VARTM), following an interply hybridization plan for the stacking sequence of hollow and solid fiber layers. An expected decrease in flexural properties and thermal conductivity was observed for the laminates with completely hollow fibers. On the other hand, hybridization had a positive effect on the laminate properties. It was shown that hybrid vascular composites could be manufactured without a significant reduction in mechanical and thermal performance by a judicious hybridization plan. The optimum hybridization of the laminate achieved a 3.1% increase in the specific flexural strength and a 5.3% decrease in thermal conductivity while containing a vascular network that can be used for active thermal control. Highlights: A vascular interply composite structure consisting of hollow and solid fibers was manufactured and characterized for the first time.The I4 composite, vascularized through the middle layers of the laminate, has almost as much flexural strength as solid composite and much more specific flexural strength.The thermal conductivity of the I4 composite is almost as much as that of the solid composite.Functional composites for thermal management and smart applications can be manufactured using hollow fibers without sacrificing flexural strength and thermal conductivity with interply vascularization. [ABSTRACT FROM AUTHOR]

3D woven tubular composites (3D‐WTC), known for their lightweight and high‐strength characteristics, are widely used in various energy‐absorbing components. To enhance the energy absorption capacity of 3D‐WTC, this study conducted a mechanical analysis of bamboo tube structures and proposed concentric circular nested biomimetic structures with "single tube + double ribs" and "double tubes + double ribs." 3D woven tubular composites with bamboo‐structures (3DWTC‐Bamboo) were fabricated using the vacuum‐assisted resin transfer molding (VARTM) process. Axial compression tests were conducted using a universal testing machine to reveal and discuss the energy absorption capacity and failure modes of 3DWTC‐Bamboo. The results showed that 3DWTC‐Bamboo with a "double tube + double ribs" concentric circular nested biomimetic structures performed exceptionally, with a peak load of 28.93KN and specific energy absorption of 7.74 J·g−1. The failure mode was a hybrid of "rib folding + tube wall buckling." Finally, finite element analysis of the stress distribution during the compression of 3DWTC‐Bamboo was conducted using ABAQUS, which validated the experimental results. In summary, this work provides a reference for structural innovation in 3D‐WTC and further expands its application in the field of energy absorption. Highlights: Propose "single tube + double ribs" and "double tubes + double ribs" structures.Introducing the "rib" structures to enhance the local strength/stiffness.Test results show that 3DWTC‐Bamboo has great potential in energy absorption.The "ribs" can increase the local strength/stiffness of the tube structures. [ABSTRACT FROM AUTHOR]

Thermoplastic resin transfer molding (T‐RTM) is one of the composites manufacturing processes using anionic ring‐opening polymerization of ε‐caprolactam (CPL). Because of very fast reaction among materials, traditional T‐RTM requires two different channels before transferring resin into the mold cavity. Single‐stream method has been researched for robust and simple process, which has several advantages in aspect of manufacturing process. Carbon fibers were preprocessed including polyamide sizing, plasma treatment and activator sizing for modified single‐channel T‐RTM. Through quantitative calculation of required sizing content, concentration of sizing agent was controlled. Thermal stability of preprocessed carbon fibers during molding was measured by TGA. Crystallinity of anionic‐polyamide 6 (A‐PA6) manufactured by single‐stream T‐RTM was measured by DSC and 3.0% lower than traditional T‐RTM. Mechanical properties were measured, which are short‐beam strength and flexural strength/modulus. The short‐beam strength and flexural strength of the composites fabricated through single‐stream T‐RTM were 29.7% and 17.0% higher than those fabricated through conventional T‐RTM while strain and toughness decreased. Fracture surface of carbon fibers/A‐PA6 composites manufactured by single‐stream T‐RTM showed more adhesive bonding between carbon fiber and matrix. Highlights: Surface treatment on carbon fibers to develop single‐channel T‐RTM process.Effects of surface treatment researched by thermal, quantitative, and IR analysis.Improved interfacial fracture mechanisms due to higher adhesion at the interface. [ABSTRACT FROM AUTHOR]

This study aims to investigate the mechanical properties of natural fiber hybrid composites, specifically those based on jute and bamboo fibers. Jute fibers made in the form of highly scattered mesh and fine‐meshed bamboo mat were selected as reinforcing materials. The highly scattered meshed jute fabric composite showed poor mechanical properties owing to resin agglomeration, leading to the brittle fracture of the composite before elongation. In contrast, the randomly oriented fine‐meshed bamboo fabric performed better in terms of both mechanical properties and strain energy absorption under the same loading conditions. Hybridization with fine bamboo mesh fibers can be a solution to improve the mechanical properties of jute fabric composites. The tensile, flexural, and in‐plane shear properties of the composites are investigated in our study. We found that hybridizing a fine‐meshed bamboo mat with jute fabric resulted in an improved mechanical performance of the composite. Composite panels have been manufactured using vacuum assisted resin transfer molding (VARTM). Experimental and numerical methods have been used to investigate the flexural behavior. Of the stacking sequences considered, the (J/B4/J) stacking showed the highest flexural strength (141.1 Mpa) and the (B2/J2/B2) 2/2 stacking sequence showed the minimum flexural strength. The alternating stacking sequence (B/J/B/J/B/J) exhibited intermediate properties. The randomly oriented bamboo fabric near the neutral axis enhanced the properties of the hybridized composite. This was verified numerically using the ANSYS ACP software. Highlights: Mechanical behavior of Hybrid composite of two natural fibers was investigated.Vacuum assisted resin transfer molding was used to manufacture composite panels.Tensile, in plane shear, 3 point flexural tests and SEM micro analysis were done.FEA was used to validate and compare the experimental and numerical results.Resin agglomeration was improved by fibers with better resin impregnation property. [ABSTRACT FROM AUTHOR]

Near-infrared (NIR) spectroscopy is employed to directly monitor the degree of cure of composite material during the curing phase in the resin transfer molding (RTM) process. The composite material consists of natural fibers and an epoxy-amine resin system. The quantitative determination of the degree of cure, α, from the NIR spectra is realized by partial least square (PLS) regression in conjunction with various pre-treatments of the spectral data. As a reference, the degree of cure is determined by isothermal differential scanning calorimetry (DSC) experiments. The best PLS model that could be obtained for α is characterized by a determination coefficient of prediction (R²P) of 0.980 and root mean square error of prediction (RMSEP) of 4.4 %. While the spectra change during curing according to the literature for each RTM trial, significant differences can be observed between the spectra of different RTM trials. The reasons for this are discussed in detail. The findings show the potential of inline NIR spectroscopy for monitoring α in the RTM process. [ABSTRACT FROM AUTHOR]

In fiber‐reinforced composites, the interfacial bonding between fibers and the matrix is crucial for determining the material's performance. A vacuum‐assisted resin transfer molding (VARTM) process was utilized in this work to fabricate glass fiber fabric‐reinforced polyamide 6 (GFF/PA6) composites through in‐situ polymerization using caprolactam (CL) as the precursor. To enhance the fiber‐matrix interfacial bonding, polyethylene glycol (PEG) was incorporated into the polymerization system, improving the hydrogen bonding between the matrix and fibers. Morphological observations and interface layer analysis revealed that the introduction of PEG resulted in improved interfacial bonding and increased interface layer thickness. Molecular dynamics simulations indicated that the amino formate groups formed by the reaction with PEG exhibited more hydrogen bonds with the hydroxyl groups on the glass fiber surface, thereby promoting interfacial bonding between the matrix and fibers. When the PEG content was 10 wt%, the tensile strength and the elongation at break of the corresponding composite increased by 160% and 300% compared to GFF/PA6 composites without PEG. This study presents a promising strategy for enhancing the fiber‐matrix interfacial bonding by modifying the matrix, offering a prospective approach for developing high‐strength thermoplastic composites. Highlights: GFF/PA6 composites were fabricated via the VARTM method.The addition of PEG for matrix modification improved the interfacial bonding.The modification enhances the hydrogen bonding between the matrix and fibers.Good interfacial bonding can greatly promote the crystallization of the matrix.The composites exhibited a significant increase in strength and toughness. [ABSTRACT FROM AUTHOR]

This study explores the impact of incorporating Halloysite Nanotubes (HNTs) nanoparticles on the low-velocity impact (LVI) behavior of carbon fiber (CF) laminate epoxy nanocomposites. The objective of this investigation was to observe the effects of different nanotube loadings (0.5 wt.% and 0.7 wt.%) on CF composites and assess their impact resistance. To achieve this, the CF was subjected to Electrophoretic Deposition (EPD) process to introduce the HNTs. Vacuum-assisted Resin Transfer Molding (VaRTM) was employed to fabricate the CF-reinforced epoxy-based laminated nanocomposites with incorporated HNTs. LVI tests were conducted following the ASTM-D-7136 standard, utilizing impact energies of 10 J and 15 J. Subsequently, the damaged areas within the composites were examined using optical microscopy (OM) and scanning electron microscope (SEM). The findings of this investigation revealed a significant enhancement in impact damage resistance with the addition of HNTs. The highest damage resistance and minimal energy absorption were observed at a loading of 0.7 wt.% HNTs. The results reveal that incorporating 0.7 wt.% HNTs substantially reduces delamination damage, influenced by absorbed impact energy. As well it composite underscores enhanced interlaminar bonding through 0.5 wt.% and 0.7 wt.% HNTs modification. Hence, we confidently assert that the addition of HNTs nanoparticles to CF/epoxy composites has considerably influenced the impact response of the nanocomposites. [ABSTRACT FROM AUTHOR]

Natural fiber composites have been extensively studied for structural applications, with recent exploration into their potential for various uses. This study investigates the impact of chemical treatments on the properties of Brazilian jute woven fabric/polyester resin composites. Sodium hydroxide, hydrogen peroxide, and peracetic acid were utilized to treat the jute fabrics, followed by resin transfer molding (RTM) to form the composites. Evaluation included water absorption, flexural strength, tensile strength, and short-beam strength. The alkaline treatment induced changes in the chemical composition of the fibers' surface. Chemical treatments resulted in increased flexural and short-beam strength of the composites, with no significant alterations in tensile properties. The hydrogen peroxide treatment exhibited lower water absorption, suggesting its potential as a viable option for enhancing the performance of these composites. [ABSTRACT FROM AUTHOR]

This paper studied the compressive behavior of a composite sandwich panel with a lozenge‐shaped core reinforced with graphene nanoparticles (GNPs) under different conditions. The fabrication process involves the utilization of Kevlar fibers and epoxy resin to construct the sandwich panels, followed by introducing polyurethane (PU) foam through vacuum‐assisted resin transfer molding (VARTM). Flat‐wise compression testing is conducted to assess the mechanical properties and behavior of the sandwich panels. The study investigates the effect of various parameters, including core angle, core height, weight percentage (wt%) of GNPs, and PU foam, on the compressive strength of the structure. The experimental results are validated through finite element simulation using ABAQUS software, and a satisfactory agreement is observed between the simulated and experimental data. The research findings indicate that the inclusion of 3 wt% of GNPs in the structure leads to a notable 25% enhancement in the compressive strength of the sandwich panel. However, when the GNP content was further increased to 0.4 wt%, a contrasting trend was observed and the strength of the structure decreased by about 12%. Furthermore, an increase in the core angle is associated with a substantial 46% improvement in the sandwich panel's strength. Conversely, an increase in the core height is found to cause an 18% reduction in the sandwich panel's strength. Also, the addition of PU foam results in a significant increase of approximately 42% and 58% in the strength and energy absorption of the sandwich panel, respectively. This comprehensive parametric study offers valuable insights to engineers and designers seeking to construct sandwich panels with optimal strength against compressive loads. Highlights: Adding GNPs modifies the mechanical properties of the sandwich panel.Adding 0.4% of GNPs leads to the reduction of the structure's strength.Increasing the core angle increases the sandwich panel's strength.Increasing the core height decreases the sandwich panel's strength.PU foam significantly increases the sandwich panel's strength. [ABSTRACT FROM AUTHOR]

Void defect is prevalent during the composite manufacturing process and may reduce the mechanical properties of composite structures, while limited information about three‐dimensional void distribution and evolution can be found due to the difficulties in void observation. In this work, void defects at different positions were detected and analyzed using x‐ray microtomography (XRM), and the random forest algorithm was implemented for segmenting components of CFRP samples. Results showed a trend of gradual rising porosity in the axial direction, with an increase of ~250% of porosity at the outlet of resin injection compared to the one at the inlet during the composite manufacturing process. The voids mainly featured with microscale between carbon fibers, with less distribution between fiber bundles and resin‐rich zones. Void defects achieved aggregation at the middle position of manufactured laminate, which is probably related to pressure interception. In the axial direction, the proportion of large‐diameter voids gradually increased, and a large volume of connected voids appeared near the outlet. Due to the shear deformation of resin and fiber and the pressure gradient effect, most of the voids showed stripe shape. The spatial orientation of voids was predominantly along the direction of resin flow and fluctuated due to fiber curl. Highlights: 3D void characteristics in CFRP were studied using the XRM technique.Void formation and the effects of fibers on void morphology were analyzed.Dynamic void transport mechanisms during CFRP manufacturing were studied.Location and morphology of voids are helpful for CFRP damage modeling.The effective partitioning of CFRP was achieved using a random forest algorithm. [ABSTRACT FROM AUTHOR]

A co-curing resin system consisting of 9368 epoxy resin for prepreg and 6808 epoxy resin for resin transfer molding (RTM) was developed. A corresponding preparation method for a novel polymer composite bolted T-joint with internal skeleton and external skin was proposed based on the prepreg-RTM co-curing process, and novel T-joints were fabricated. A series of conventional configuration T-joints based on the RTM process and T-joints made of 2A12 aluminum alloy were prepared simultaneously. Bending performances were studied on these T-joints experimentally. The results indicate that 9368 epoxy resin and 6808 epoxy resin exhibit good compatibility in rheological and thermophysical properties. The novel T-joints prepared with the prepreg-RTM co-curing process show no obvious fiber local winding or resin-rich regions inside, and the interface quality between the internal skeleton and the external skin is excellent. The main failure modes of the novel T-joint under bending load include the separation of the skin and skeleton and the fracture along the thickness on the base panel; the skeleton carries the main bending load, but there is still load transfer between external skin and internal skeleton through their interface. The internal damages of the novel T-joint are highly consistent with surface damages observed visually, facilitating the detection and timely discovery of damages. The initial stiffness, damage initiation load, and ultimate load of the novel T-joint are 1.65 times, 5.89 times, and 3.45 times that of the conventional T-joint, respectively. When considering the influence of the density, the relative initial stiffness and relative ultimate load of the novel T-joint are 1.44 times and 2.07 times that of the aluminum alloy T-joint, respectively. [ABSTRACT FROM AUTHOR]

A new process technique called rapid heat cycle molding (RHCM) has been developed using a carbon nanotube (CNT) web film as a heat source for the mold. Although various heating technologies have been applied as RHCM techniques, low energy efficiency has caused productivity to decrease. To improve this issue, the RHCM process was implemented using a CNT web film for more efficient heating. A multilayer structure module was designed to apply the CNT web film to a full-size injection mold. The RHCM process was implemented by designing stable heat transfer and electrical insulation through a multilayer structure module. When power was applied, the temperature rose quickly, with the highest heating rate reaching 41 °C/s at 40 kW, and the highest temperature achieved at about 300 °C. The temperature uniformity and stability were tested on 6 points of the cavity surface, and an average of 97% temperature uniformity and stability was observed during heating. In production testing of the Center Fascia (CTR.FASCIA), which is an internal automobile part made of polycarbonate/polybutylene terephthalate composites, an RHCM process was conducted. The width and depth of weld lines in the molded products were eliminated, and a 26% improvement in glossiness and surface quality was observed compared to the conventional injection molding process (CIM). CNT web film is a versatile and flexible material that can be applied in various forms, and it has been confirmed that by utilizing this material to create a multilayer structure module, the RHCM process can be performed reliably. [ABSTRACT FROM AUTHOR]

Graphene nanoplatelets (GNPs) are extremely useful nanofillers in epoxy in carbon fiber‐reinforced polymer (CFRP) composites as they make CFPRs sustain higher loads before failure in different kinds of loading for example flexural, tensile and fatigue. The current study aims to investigate the effect of GNP coating on carbon fibers on the deformation modes of CFRPs under flexural loading. Laminates have been fabricated using vacuum‐assisted resin transfer molding (VARTM) after spray coating GNPs on unidirectional carbon fiber fabrics. One set of flexural tests were carried out where the strain was recorded using DIC and the other set had in‐situ deformation while recording optical images to monitor deformation. Since, the most probable causes of failure under flexural loading are local compression, shear or contact stresses due to a sharp ram, other mechanical tests like compression test and nano‐indentation were also carried out on the composites. Compressive stress–strain response was ascertained using combined loading compression (CLC) fixture and digital image corelation (DIC) while contact response was evaluated using nanoindentation. GNP‐coated CFRPs were shown to have an increase in compressive modulus of 16% and failure strain of 6%, respectively. Axial and transverse strains measured through DIC were more than two times higher in GNP‐coated CFRPs. Nano‐indentation tests across the entire composite showed some data with intermediate modulus (~10–45 GPa) and hardness (~1–5 GPa) between the epoxy and the fiber and this corresponded to an interphase region which was thicker in 0.4GNP laminate compared to pristine laminate. Flexural strength, flexural modulus and strain at maximum stress improved by 10%, 8%, and 9% respectively in GNP‐coated CFRPs compared to uncoated CFRPs. In addition, while pristine laminates showed non‐uniform distribution of strains during flexural loading, the distribution of strains was much more uniform in GNP‐coated laminate. However, in both kinds of laminates, the failure initiation was in the region of compressive bending stresses. Highlights: GNP‐added laminate showed an intermediate modulus and hardness interphase through a nanoindentation test.Digital image correlation analysis has been performed to obtain the strain maps during compressive and flexural loading.GNP‐added laminates showed higher failure strains compared to pristine laminates under the compressive loads.GNP‐added laminates performed well under flexural loading. [ABSTRACT FROM AUTHOR]

The aim of this work is to analyze the effect of water absorption on the mechanical properties and damage mechanisms of polyester/glass fiber/jute fiber hybrid composites obtained using the compression molding and vacuum-assisted resin transfer molding (VARTM) techniques with different stacking sequences. For this purpose, the mechanical behavior under tensile stress of the samples was evaluated before and after hygrothermal aging at different temperatures: TA, 50 °C, and 70 °C for a period of 696 h. The damage mechanism after the mechanical tests was evaluated using SEM analysis. The results showed a tendency for the mechanical properties of the composites to decrease with exposure to an aqueous ambient, regardless of the molding technique used to conform the composites. It was also observed that the stacking sequence had no significant influence on the dry composites. However, exposure to the aqueous ambient led to a reduction in mechanical properties, both for the molding technique and the stacking sequence. Damage such as delamination, fiber pull-out, fiber/matrix detachment, voids, and matrix removal were observed in the composites in the SEM analyses. [ABSTRACT FROM AUTHOR]

Technological advancements are exacting futuristic materials that exhibit comprehensive properties for diversiform applications. Cyanate Esters (CE) are promising materials that can suffice the current and future demands for myriad applications. This is possible because they exhibit multitudinal properties such as nominal density 1.17 g m 3 , high dimensional stability, low moisture absorption (0.5–2.5 wt%), high-temperature operating conditions (> 300 °C), low loss factor (tan δ = 10 - 3 to 6* 10 - 3 ), low dielectric constant k = 2.6 - 3.1 F m , EMI shielding, low defect density, strong wave permeability, thermo-mechanical and, chemical stability, excellent UV aging resistance, radiation resistance, excellent adhesion to conducting metals up to 250 °C, resistance to microcracks, glass transition temperature (240–290 °C), and good processability. CE's multifunctional properties paved the way for the exploitation as the matrix material in composites, an ideal thermoset for blending with various thermosets and thermoplastics resulting in phenomenal properties. CE is considered a desirable thermoset matrix for industrial applications due to its ability to meet the desired qualities, such as low cost, compatibility with conventional techniques, excellent shelf life, low curing temperature, high-temperature resistance, and low flammability. Moreover, CE-based composites and blends can be conveniently fabricated using existing techniques commonly employed for epoxy-based materials like resin transfer molding and filament winding, eliminating the need for developing new processing techniques. This review focuses on CE-based wave transparent composites, functionalization of fibers for better interfacial compatibility, shape memory polymers (SMP), EMI shielding effectiveness (EMI SE), and dielectric properties enhancement for various applications. [ABSTRACT FROM AUTHOR]

The usage of basalt fiber in the engineering industries has gained significant interest due to its characteristics such as alkali resistance and enhanced mechanical properties. Similarly, E-glass-fiber-reinforced composites have been widely used in the fabrication of electrically resistive industrial components such as switches, circuit panels, and covering cases. In the present study, the tensile, flexural, thermogravimetric, and low-velocity impact characteristics of various percentages of basalt/E-glass-fiber-reinforced polymer composites fabricated via vacuum-assisted resin transfer molding were investigated. The results show that a higher volume percentage of basalt (39%) significantly enhances the impact resistance up to 45% with a moderate improvement in flexural properties. The higher the vol % of E-glass (40%), the more the tensile and flexural properties are increased, i.e., 185 N/mm2 and 227.87 N/mm2, respectively. It is concluded that by choosing the optimum hybridization method, impact resistance and other mechanical properties can be improved significantly. The thermogravimetric analysis results show that PC313534 (35 vol % basalt and 34 vol % E-glass) possesses the lowest decomposition temperature of 381.10 °C. The results from the present study indicate that the polymer composite fabricated in the present study is suitable for applications where higher structural-load-resistive properties are required. [ABSTRACT FROM AUTHOR]

Traditional microstrip antennas have problems with heavy weight and poor gain. In order to reduce the weight of the antenna itself and improve its gain, the preforms of the 3-D woven rectangular hollow structure conformal bearing microstrip antenna (3DWRHS-CB-MA)with different heights were woven from ultra-high molecular weight polyethylene (UHMWPE) filament yarns and copper wires on a common loom through reasonable design. The preform was used as the reinforcement and epoxy resin was used as the matrix, four different heights (2, 4, 6, and 8mm) of 3DWRHS-CB-MA were prepared by vacuum-assisted resin transfer molding (VARTM) process. Finally, the electromagnetic performance was analyzed by high-frequency structure simulator (HFSS) and experimental testing. The results showed that the frequency deviation of the 2 mm height microstrip antenna was minimal; while the 4 mm height microstrip antenna had better gain efficiency and directional diagram compared to others. The 4 mm height microstrip antenna has good radiation performance with a weight of only 35 g which shows that 3DWRHS-CB-MA are potential candidates for future intelligent textile materials and wireless communication fields. Highlights • Weaving with UHMWPE filament yarns and copper wires on common looms. • The preform was used as the reinforcement, and epoxy resin was used as the matrix. • Simulation of electromagnetic characteristics of antennas using HFSS software. • Proving the effectiveness of the electromagnetic simulation model. • Revealing the electromagnetic radiation mechanisms. [ABSTRACT FROM AUTHOR]

The mechanical behavior of composites, made of an epoxy resin matrix reinforced by 30 and 40% of a satin cloth from long Alfa, sisal and hybrid Alfa/sisal fibers was studied. The fibers are obtained by extraction with elimination of binders such as pectins and lignin. For each type of fibers, appropriate and optimal chemical and thermal treatments were conducted within NaOH solution, to enhance both the fiber surface quality and the interfacial bonding between fibers and matrix. Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and chemical decomposition of treated and untreated fibers lead to prove the treatment efficiency. The thermogravimetric (TGA) and differential thermogravimetric (DTG) analyses showed better thermal stability. Differential scanning calorimetry (DSC) made it possible to quantify the enthalpy changes which showed an increase in the amount of heat as a function of the increase in weight fraction of natural fibers. The endothermic reaction of the composites studied containing 30 wt% fiber reinforcement was less than that containing 40 wt% fiber reinforcement. The composite materials were produced by vacuum assisted resin transfer molding (VARTM) method due to hydrophilic nature of the fibers. The results of static tests were compared to those of pure epoxy resin. It showed a significant increase for 40 wt% woven A1lfa/epoxy of about 333, 113, and 81% in tension, 3-points bending and compression tests respectively. SEM morphology analysis revealed good interfacial adhesion between the treated fibers and the matrix. [ABSTRACT FROM AUTHOR]

Fiber-reinforced polymer composites are manufactured using various methods, with vacuum-assisted resin transfer molding (VARTM or VARIM). This study's primary focus lies in assessing how the orientation of sampling impacts the mechanical properties of glass fiber-reinforced pure and nanocomposites. 2 wt.% nano Al2O3- doped and non-doped composites were produced using the VARTM process. Tensile, flexural, and density test specimens were extracted from three distinct zones and two distinc direction those aligned horizontally to the resin flow (HRF) and those oriented vertically to the resin flow (VRF). Remarkably, results showed up to a 3.91% increase in values from samples in the third zone, particularly on the vacuum outlet side. To facilitate precise stress value comparisons across plates, uniform sample orientation and consistent zone selection are essential. [ABSTRACT FROM AUTHOR]

Fabricating bamboo fiber‐reinforced epoxy composites (BFREs) using the vacuum‐assisted resin transfer molding (VARTM) process has many advantages, such as low cost, high product quality, controllability, and broad applicability. However, the immature fabrication process seriously affects product performance and hinders the full exploitation of the advantages of the VARTM process. The effects on the physical‐mechanical and thermal properties of BFREs by molding sequence and fiber content were investigated in this study. The molding sequence of fiber compression followed by resin injection was beneficial to ensure hermeticity, thus reducing the voids in the BFREs. The mechanical properties of BFREs gradually increased with increasing fiber content. With 50 wt% fiber content, the bending strength and modulus, shear strength, and impact toughness of BFREs reached 71.27 MPa, 6.78 GPa, 11.68 MPa, and 5.45 kJ/m2, respectively. Although the thermal stability of the BFREs was slightly lower than that of pure epoxy, the bamboo fibers' high rigidity evidentially increased the epoxy's dynamic mechanical properties. The life cycle assessment indicated that the BFREs effectively reduced the environmental impacts and production energy consumption compared to the glass fiber correspondent. The VARTM‐fabricated BFREs have great potential for construction, transportation, household items, packaging, sports equipment, and leisure goods applications. Highlights: Fiber compression followed by resin injection could ensure great hermeticity.Micro‐CT accurately measured the void characteristics of the composites.Voids had detrimental effects on the properties of the composites.Dense bamboo fiber preforms enhanced the mechanical properties of epoxy.Bamboo fibers reinforcing epoxy reduced the impact on the environment. [ABSTRACT FROM AUTHOR]

During the production of fiber-reinforced plastics using resin transfer molding (RTM), various characteristic defects and flaws can occur, such as fiber displacement and fiber waviness. Particularly in high-pressure RTM (HP-RTM), fiber misalignments are generated during infiltration by local peaks in the flow rate, leading to a significant reduction in the mechanical properties. To minimize or avoid this effect, the manufacturing process must be well controlled. Simulative approaches allow for a basic design of the mold filling process; however, due to the high number of influencing variables, the real behavior cannot be exactly reproduced. The focus of this work is on flow front monitoring in an HP-RTM mold using phased array ultrasonic testing. By using an established non-destructive testing instrument, the effort required for integration into the manufacturing process can be significantly reduced. For this purpose, investigations were carried out during the production of test specimens composed of glass fiber-reinforced polyurethane resin. Specifically, a phased array ultrasonic probe was used to record individual line scans over the form filling time. Taking into account the specifications of the probe used in these experiments, an area of 48.45 mm was inspected with a spatial resolution of 0.85 mm derived from the pitch. Due to the aperture that had to be applied to improve the signal-to-noise ratio, an averaging of the measured values similar to a moving average over a window of 6.8 mm had to be considered. By varying the orientation of the phased array probe and therefore the orientation of the line scans, it is possible to determine the local flow velocities of the matrix system during mold filling. Furthermore, process simulation studies with locally varying fiber volume contents were carried out. Despite the locally limited measuring range of the monitoring method presented, conclusions about the global flow behavior in a large mold can be drawn by comparing the experimentally determined results with the process simulation studies. The agreement between the measurement and simulation was thus improved by around 70%. [ABSTRACT FROM AUTHOR]

In this article, local defect resonance-based vibrothermography has been studied for different sweep direction and ranges. Two different carbon fiber-reinforced polymer (CFRP) composite plate has been fabricated from vacuum assisted resin transfer molding. In the first plate, a flat bottom hole has been made and two barely visible impact damages are created in other plate. The area of delamination has been determined from phased array ultrasound testing. Laser doppler vibrometry (LDV) has been performed first for different sweep ranges and directions. The CFRP plate is excited with a piezoelectric element at 150 Vpp and the vibration over defect area is captured using a single point laser doppler vibrometer, operating in scanning mode. It has been found that vibration amplitude at local defect resonance (LDR) frequency increases in narrow sweep range compared to a wideband excitation. Again, in both cases, it has been found that backward sweep produces more amplitude compared to forward one due to softening nonlinearity. An asymmetry in LDR frequency is also been observed when the sweep range is further narrowed. An uncooled microbolometer camera is used for reception in case of vibrothermography. Backward sweep is found to be more effective as compared to the forward one and the temperature increment increases in case of narrowband excitation range. [ABSTRACT FROM AUTHOR]