Search

Highlights High‐performance electromagnetic absorption (EMA) materials were becoming increasingly in demand as radar technology advances. One significant way to increase the performance of EMA composite structures was through flexible design. In this work, three‐dimensional (3D) woven preforms with varying absorption layers and structures were woven on an ordinary loom. Subsequently, the vacuum‐assisted resin transfer molding (VARTM) molding method was used to prepare 3D woven EMA materials with good EMA capabilities. Then, experimental research examined the impact of varying fiber yarns, absorption layers, and incidence angles (θ) on the EMA characteristics of the 3D woven EMA materials. Lastly, Computer Simulation Technology (CST) electromagnetic simulation was used to simulate the optimal experimental result and Radar Cross Section (RCS). The results demonstrated that changing fiber yarn structure of 3D woven EMA materials can significantly improve the EMA capabilities of the 3D woven EMA materials. Simultaneously, the EMA capabilities of the 3D woven EMA materials was influenced considerably by the number of the absorption layers and the incidence angle of the electromagnetic wave. For example, the six‐layer 3D woven EMA materials (A(A2C)3C) with carbon fiber yarns introduced in the Z‐direction yarns achieved an effective absorption bandwidth of up to 8.34 GHz at a thickness 9 mm. At an incidence angle of 90°, the most excellent reflection loss value of −44.25 dB could be attained. At the same time, the shortcomings of the experiments were further optimized by CST, and RCS understood the suitability of the EMA materials. This study provided a vital research methodology for designing and developing high‐performance EMA materials. 3D preforms were woven on an ordinary loom. The VARTM was used to prepare 3D woven EMA materials. Introduction of carbon fiber yarns to improve EMA capabilities. The shortcomings of the experiments were further optimized by Computer Simulation Technology. Understood the suitability of the EMA materials by Radar Cross Section. [ABSTRACT FROM AUTHOR]

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]

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]

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]

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]

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]

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]

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]

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 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]

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]

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]

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]

In the current study, the friction and wear properties of Furcraea foetida fiber‐reinforced epoxy composites were investigated. This study evaluated the effect of Furcraea foetida fiber content on the tribological behavior of composites. A water‐retting method was employed to extract the fibers, and resin transfer molding was used to fabricate the composites. The frictional force, coefficient of friction (COF), and wear rate were measured under dry test conditions and various applied loads (80, 100, 120, and 140 N). Microstructural analysis was conducted using scanning electron microscopy to investigate the surface morphology and wear mechanisms of the composites. The results revealed that the composite with 50 vol% of fibers exhibits the lowest frictional force and COF in both normal and parallel orientations with overall average COF of 0.43 in normal orientation and 0.42 in parallel orientation. Moreover, the composite with 60 vol% demonstrates the best wear resistance with an overall average specific wear rate of 2.1982 × 10−5mm3/Nm in normal orientation and 4.3478 × (10−5) mm3/Nm in parallel orientation. Overall, this study provides valuable insights into the tribological behavior of Furcraea foetida fiber‐reinforced epoxy composites and identifies the optimal volume fractions for improved friction and wear performance. Highlights: Higher vol% yields denser composites with minimized voids.Normal fiber orientation shows maximum SWR of 10.0614 × (10−5) mm3/Nm.Optimal frictional force and COF in 50 vol% composite.Enhanced wear resistance observed in 60 vol% composite.Higher vol% increases interfacial bonding and wear resistance in composites. [ABSTRACT FROM AUTHOR]

In the process of preparing textile composites by resin transfer molding (RTM) method, both the upper and lower surface of the mold will interact with the composite parts due to the mismatch of thermal expansion coefficient between the mold and the part, resulting in warpage deformation. To address this key technical problem, this article first studied the effect of mold on the warpage deformation of composite material under different fiber volume fractions. Then a mold–part interaction modeling method for RTM process with nonthermoelastic deformation is proposed. By introducing shear layers between the upper and lower surfaces of the mold and the composite part, a finite element simulation model for predicting the curing deformation of the component is established and experimentally verified. The results show that the effect of mold–part interaction on the warpage deformation of the composite decreases with increasing fiber volume fraction. Meanwhile, the proposed modeling method can avoid complete material characterization, and the comparison between experimental and simulation results proves that the model can accurately simulate the curing deformation of composite components under the same process conditions. Finally, the analysis reveals that the interaction caused by thermal mismatch between the composites and the mold is less related to the intermediate layup, but mainly related to the fiber orientation of the layup layer in contact with the mold. Highlights: The warpage deformation law of the mold on the composites with different fiber volume fractions is investigated.A mold–part interaction modeling method for a resin transfer molding process with nonthermoelastic deformation is proposed, where the mold stretching effect is represented by the cumulative effect of the interaction between the two layers on the upper and lower surfaces of the part. [ABSTRACT FROM AUTHOR]

The present work deals with the thermal behavior investigation of new biocomposite materials intended to be used for process engineering applications. Particular attention is given to the thermal degradation of such materials. Thermal characterization at different scales is performed using thermogravimetric analysis (TGA) and cone calorimeter experiments. The main purpose is to compare the thermal behavior of new bamboo‐based and banana‐based Green Biocomposites (GBCs). An intumescent fire retardant (IFR) coating, which is a mixture of APP and boric acid was applied on the GBC sample surface to study the flame retardancy. The GBC samples was first manufactured using a vacuum resin transfer molding. TGA results showed that bamboo‐based (BM‐GBC) and banana‐based (Bn‐GBC) materials exhibits similar thermal degradation pattern. While cone calorimeter experiments revealed that BM‐GBC outperforms than Bn‐GBC. The IFR coating improved the flame retardancy of both GBCs by reducing the heat release rate as well as a noticeable reduction in terms of smoke emission. Finally, to improve the thermal stability of Bn‐GBC material, SiC powder is added as a filler. The IFR coating and SiC powder addition promotes considerably the thermal behavior of Bn‐GBC materials. [ABSTRACT FROM AUTHOR]

The in‐situ anionic polymerization of ε‐caprolactam (ε‐CL) to polyamide‐6 enables the production of large, near net shape fiber reinforced composites by thermoplastic resin transfer molding. For the propagation of the flow front as well as for the progress of the solidification, the simultaneous processes of polymerization and crystallization and the corresponding reaction kinetics play a central role. To investigate these processes, preparation of reactive mixtures consisting of ε‐CL, activator, and initiator was carried out under inert atmosphere. A solvent‐based activator and initiator were used, which hardly have been studied in the literature so far. In analogy to the resin transfer molding process, quasi‐isothermal differential scanning calorimetry measurements were performed at various temperatures and the released enthalpy and the degree of crystallization were determined. From these isothermal measurements, a two‐stage semi‐empirical kinetic model was established for a solvent‐based system for the first time, which reproduces the experimental data with high precision. To apply the obtained kinetic model to a thermoplastic resin transfer molding process it was finally correlated to dielectric sensor data, allowing real‐time prediction of the total conversion. [ABSTRACT FROM AUTHOR]

Self‐healing composites are promising for engineering, but self‐healing structures or components usually induce reduction in the composite's mechanical properties. In this paper, core‐shell nanofibers which accommodating healing agent in the core and incorporating carbon nanotubes (CNTs) in the shell were produced to develop non‐destructive self‐healing carbon fiber/epoxy (CF/EP) composites. The epoxy resin and curing agent were encapsulated in CNTs‐reinforced polyacrylonitrile (PAN) core‐shell electrospinning nanofiber mats and the mats were placed on carbon fibers to fabricate CF/EP composite laminates by the vacuum‐assisted resin transfer molding (VARTM) process. The results indicated that the flexural strength, flexural modulus, tensile strength, tensile modulus, and Mode II interlaminar fracture toughness of composites with suitable self‐healing components increased by 49%, 44%, 8%, 13%, and 43%, respectively, compared to the pristine CF/EP. The healing flexural strength of the composite with 1 wt% CNTs recovered up to 93.57%, observed 24 h after the bending fracture, which is higher than the initial strength of CF/EP composites without self‐healing components. The research indicates that self‐healing composites can be developed without mechanical properties degrade and even achieve stronger mechanical properties. [ABSTRACT FROM AUTHOR]

The recycling of carbon fiber (CF) reinforced bio‐based degradable epoxy resin composites is of great significance for resource saving, environment protection and sustainable development of economy and society. Resin transfer molding (RTM) has been recognized as one of the most promising processes to manufacture CF Reinforced polymeric composites cost‐effectively. The bio‐based diglycidyl ether pentaerythritol vanillin diacetal (DEPVD) epoxy resin used in this study is an epoxy resin that can be degradable under mild conditions. And its CF composites were prepared by the RTM process using DDS as a curing agent and low viscosity bisphenol A‐E51 epoxy resin as a diluent. The chemical rheological properties, curing behavior, thermal stability, dynamic viscoelasticity and mechanical properties of DDS‐E51‐DDS epoxy resin were investigated. It is found that the increase of DEPVD content is beneficial to improve the mechanical properties, Tg and solid residue after thermal degradation of DEPVD‐E51‐DDS epoxy resin. Moreover, the effects of DEPVD content in epoxy resin on the mechanical properties of CF/DEPVD‐E51‐DDS composites were evaluated. When the DEPVD content is 70%, the tensile and flexural strength of CF/EPVD‐E51‐DDS composites are 1649.4 MPa and 1207.4 MPa, respectively. The degradability and mechanism of CF/DEPVD‐E51‐DDS composites were further investigated. CF/DEPVD‐E51‐DDS composites containing 70% DEPVD have excellent degradability, and the recycled CFs exhibit comparable mechanical properties to the virgin CFs, which demonstrates a novel way to recover the high‐quality of used CFs. [ABSTRACT FROM AUTHOR]

Carbon fiber fabric reinforced poly(lactic acid) (CFF/PLA) composites were manufactured using both vacuum‐assisted resin transfer molding (VARTM) and compression molding (CM) methods. Of the two methods, the CFF/PLA‐VARTM composite shows superior carbon fiber infiltration and interfacial adhesion compared to the CFF/PLA‐CM composite. The improved infiltration enables the carbon fibers to induce a dense group of PLA crystal nuclei along their surface, resulting in the formation of a trans‐crystalline layer (TCL) structure where the PLA lamellae grow perpendicular to the fiber axis. As a result, the interfacial adhesion is improved, and the crystallinity of the PLA in the CFF/PLA‐VARTM composite is 4.1 times higher than that of pure PLA. However, the weak infiltration of fibers and matrix in CFF/PLA‐CM composite results in poor load‐bearing ability. Conversely, CFF/PLA‐VARTM composite presents better interlayer bonding and tight fiber‐matrix wrapping, promoting effective tensile load transfer to carbon fibers, which results in higher strength and modulus. The presence of TCL structures also plays a key role in improving mechanical properties. Overall, these findings demonstrate a promising method for producing high‐performance PLA composites. [ABSTRACT FROM AUTHOR]

A new portable resin injection device has been developed to repair barely visible impact damage (BVID) in carbon fiber reinforced polymer (CFRP) laminates. Repair was conducted on damaged 16‐ and 24‐ply laminates at two different ambient pressures, that is, atmospheric pressure and vacuum, using three different adhesive types, that is, neat epoxy, epoxy blended with respective halloysite nanotubes (E1HNT) and carbon nanotubes (NF100). The repair effectiveness was assessed by infrared thermography and in‐plane compression testing. All damaged laminates suffered significant degradation in fracture properties as compared to pristine laminates. According to Taguchi method, the main factor affecting the repair efficiency is the laminate ply number. The findings revealed that the optimal repair parameters corresponds to using neat epoxy or E1HNT in vacuum could restore the elastic properties and using E1HNT adhesive at atmospheric pressure could restore the fracture properties of damaged 16‐ply laminate after repair. Regardless of repair parameters, the repair efficiency for the mechanical properties of 24‐ply laminates revealed minimal restoration to the laminate pristine conditions after repairing the damaged laminates due to the complexity of BVID for allowing the adhesive to infiltrate and filled the crack structures. The choice of repair parameters was discussed based on the effectiveness of restoring elastic and fracture properties. [ABSTRACT FROM AUTHOR]

Software-based mold flow analysis is often performed to confirm optimized resin pipe arrangements. In this study, the GeoDict software and reverse scanning were employed to develop a method for performing rapid porosity and permeability estimation. A comparison of the results from one-dimensional resin flow and Easyperm tests revealed a 10% variation in the porosity and permeability parameters obtained through the proposed rapid estimation method. In addition, the obtained parameters were substituted into a Moldex3D model to simulate the resin flow on the personal watercraft hull during vacuum-assisted resin transfer molding (VARTM). A comparison of simulation results and hull infusion results revealed that the integration of the proposed rapid estimation method with Moldex3D allowed for the accurate simulation of the resin flow in large fiber-reinforced-plastic (FRP) products (variation <8%). The proposed method can be applied to large wind turbine FRP parts and large FRP yacht components to increase process planning efficiency and product stability. [ABSTRACT FROM AUTHOR]

Variable thickness composites are essential engineering materials which have been used in various high‐performance products. However, the commonly used variable thickness composites are mainly lamination, which is prone to delamination and reduce the overall performance under load. To solve this problem, 3D woven fabrics with integrity and continuous variable thickness have been designed and weaved on ordinary looms using basalt yarns. The resin‐based variable thickness composites have been prepared by vacuum‐assisted resin transfer molding (VARTM) process, and two different laminated composites have been produced for comparison. Compared with the two kinds of laminations, the bending strength of the 3D woven variable thickness (3DWVT) composites is increased by 12.28% and 16.22% under positive load; 16.74% and 17.08% under negative load. Finally, the meso‐finite element simulation analysis of the bending performance of 3DWVT composites was carried out by using the meso‐finite element analysis (FEA), and the damage mechanism and failure mode were explored. [ABSTRACT FROM AUTHOR]

Void formation as a result of irregular resin flow at the flow front is discussed and a practical method for reducing void formation during resin transfer molding (RTM) is introduced. In this study, a sensor system is developed for in situ measurement of resin velocity inside a closed cavity. Assisted by the acquired data, a resin injection system is augmented to automatically adjust the injection pressure and achieve a uniform flow front velocity. It is proven, that the developed system is suited to monitor the resin flow front and is able to sufficiently control flow velocity of a linear flow front. Test specimen produced by this method show significantly reduced void contents in comparison to a common resin transfer molding process. [ABSTRACT FROM AUTHOR]

To avoid the narrow absorption bandwidth and delamination in uniform honeycomb composites, three‐dimensional (3D) gradient honeycomb composites were prepared through a vacuum‐assisted resin transfer molding (VARTM) process. The 3D gradient honeycomb woven composite (3D GHWC) was made by using 3D gradient woven fabric with basalt and carbon fibers as reinforcement and epoxy resin mixed with carbon black and carbonyl iron powder as the matrix. For further optimization of the effective absorbing bandwidth and/or reflection loss (RL), especially at a specific incident angle, the type of absorbing agent and gradient honeycomb structure could be altered in the weaving process. The minimum RL value achieved by the 3D GHWC with 18.5‐mm thickness is −47 dB in the C band at a 30° incident angle using an Agilent vector network analyzer. In addition, the bending strength of the 3D GHWC with 18.5‐mm thickness reaches 101.7 MPa by a universal testing machine, which suggests excellent mechanical properties and ultra‐strong environmental adaptability of the 3D GHWC material. This work offers an adjustable method for the fabrication of microwave absorption (MA) composites, showing potential prospects in civilian and military MA applications. [ABSTRACT FROM AUTHOR]

Composite materials have the characteristics of light weight, high strength, high modulus, and corrosion resistance. In this article, glass fiber/PVC curved sandwich structure composites with three curvature radiuses (80, 150, and 260 mm) and different sandwich structures were prepared by vacuum assisted resin transfer molding. The specimens were subjected to quasi‐static indentation test and drop hammer impact test. The influence of curvature radius and ply sequence on the impact behavior of composites were analyzed by comparing the load displacement curve, pit depth, and energy loss. The compression after impact of specimens with different curvature radius and structure was carried out to explore the damage limit and toughness of composites. It is found that the maximum tensile properties of sandwich specimens are determined by the degree of resin infiltration into PVC foam panels. The impact performance is mainly attributed to the laying sequences of reinforcement. The instantaneous impact performance of free falling body is greatly affected by the curvature radius, and the post impact compression performance of sandwich composites is increased with increase of the curvature. The research could provide a theoretical basis for the application of combining curved surface and sandwich structure composites. [ABSTRACT FROM AUTHOR]

In the design of structural composite components for aerospace applications, durability and reliability play a very significant role. To assess the reliability of these material it is essential to carry out robust experimental tests on several specimens and under different loading conditions to allow the determination of fundamental fracture parameters. Fracture toughness, in particular, allows the quantification of the material strength to fracture. This work proposes a study on non‐crimp fabric (NCF) together with a two‐component epoxy resin. The selected system has been selected based on its suitability to produce aerospace‐approved components using resin transfer molding (RTM) process. The fabric adopted is a SAERTEX NCF with very high modulus and strength, whereas the resin is BDP 4294. This work shows the methods, equipment, and results of an experimental campaign carried out to determine the fracture toughness of the manufactured NCF composite material. Finally, to quantify the fracture toughness of the NCF composite material, Mode I, II, Mixed Mode I–II, and translaminar fracture tests were also considered. Highlights: Manufacturing of panels with specific resin for aeronautical applications.Fracture toughness tests for durability and reliability assessment.Mode I and Mode II fracture toughness tests and calculations.Mixed Mode I–II fracture toughness tests and calculations.Translaminar fracture toughness tests and calculations. [ABSTRACT FROM AUTHOR]

In this study, the behavior of pure glass fiber/epoxy, pure carbon fiber/epoxy, interply hybrid, and locally nested intraply hybrid composites under tensile load was investigated. The specimens were produced by the vacuum‐assisted resin transfer molding (VARTM) method. Interply hybrid composites showed approximately the average tensile strength of the glass and carbon fiber/epoxy composites, with 603 MPa. Intraply hybrid composites had 17% lower tensile strength than pure glass fiber/epoxy composites due to the discontinuity of the fibers in the structure. Therefore, pure or interply hybrid composites are suitable in cases where tensile strength is more important, while in special cases where different properties are desired in different regions of a monolithic structure, locally nested intraply hybrid composites can be used. While the finite element analysis (FEA) results of pure and interply hybrid composites were very close to the tensile test, the amount of deviation increased in intraply hybrid composites due to fiber discontinuity. Fiber and void volume fractions of hybrid specimens were found to be around 62% and 1.45%, respectively. The numerical and experimental results of pure carbon fiber/epoxy composite are validated by the analytical solution. [ABSTRACT FROM AUTHOR]

This study's aim was to research the ultimate loads and failure modes of single‐bolted pultruded glass‐fiber‐reinforced polymer (PGFRP) connections reinforced by glass fiber sheets (GFSs) under pin‐bearing conditions. In total, 144 specimens with various geometric parameters of GFRP bolted connections with different ratio values of the end distance of PGFRP plate to bolt diameter (e/d) and various ratio values of width of PGFRP plate to bolt diameter (w/d) were considered, and their results are here discussed (e/d = 2,3,4 and w/d = 2,3,4,5). Three types of GFSs (0°/90° GFSs, ±45°GFSs, and chopped strand mat GFSs) were molded by the vacuum‐assisted resin transfer molding (VaRTM) method and used to strengthen the connections. The results show that all three types of GFSs had good effects on the increase in the ultimate load of the connections. In addition, the strengthening effects were decreased with the increase in the e/d ratio of the connections for all types of GFSs. Moreover, theoretical equations were suggested to forecast the ultimate loads and failure modes of pin‐bearing single GFS‐strengthened PGFRP connections with high accuracy (less than 12% deviation). [ABSTRACT FROM AUTHOR]

As an important thermosetting resin, epoxy resin (EP) is widely used in the field of composite materials. Long storage time, rapid curing and low viscosity of one‐component EP is ideal for preparing composite materials by vacuum assisted resin transfer molding (VARTM). For this sake, we developed and synthesized a new imidazole thermal latent curing agent, 4,7‐diimidazol‐2,1,3‐benzothiadiazole (BTD‐MZ2) with a yield of about 75%. The curing behavior, thermal stability and storage time of the prepared EP system was studied by differential scanning calorimeter (DSC), thermal gravimetric analyzer (TGA), modular compact rheometer (MCR), respectively. DSC results showed that EP/17.5 wt% BTD‐MZ2 had a good latent period at low temperature, and can rapidly cure EP when heated to 150°C. TGA results show that BTD‐MZ2 promoted the formation of carbon residue and the residual carbon rate of EP/17.5 wt% BTD‐MZ2 is as high as 37.9%. MCR results show that the storage time of EP/17.5 wt% BTD‐MZ2 at 60°C can reach 850 min. In addition, it could play a role of catalyst used as co‐curing agents with aromatic amines for EP. DSC test showed that the addition of 5 wt% BTD‐MZ2 reduced the activation energy of EP/4,4′‐diaminodiphenylmethane (DDM) and promoted the curing reaction. [ABSTRACT FROM AUTHOR]

This article has experimentally and numerically investigated the high‐velocity impact resistance of the composite sandwich panel with an M‐shaped lattice core reinforced by nano‐SiO2. For this purpose, firstly, a glass fiber resin epoxy sandwich panel has been fabricated in the laboratory. In this regard, the vacuum‐assisted resin transfer molding (VARTM) method has been used to achieve a laminate without any fault. In order to improve the impact resistance of the composite, the nano‐SiO2 were added to the resin epoxy matrix as filler with the ratios of 1%, 2%, and 3% of the composite's total weight. A scanning electron microscope (SEM) has been utilized to observe the microscopic structure of the composites, and it shows an exceptional homogeneous mixture of nano‐SiO2 particles in the resin epoxy matrix. From the experiment results, it was figured out that by adding 1 to 3 wt% of nano‐SiO2 into the composite, the output velocity of the projectile decreases. On the other hand, the results showed that when the projectile collides with the core of the sandwich panel, it remains in the sandwich panel and its output velocity will be zero. However, when the projectile does not completely collide with the core, the output velocity of the projectile will not be zero. In order to validate the results, a finite element analysis (FEA) has been developed to simulate the high‐velocity impact test. Then the experimental data has been compared to numerical simulation and good agreement was observed. [ABSTRACT FROM AUTHOR]

A methodology using neat resin characterization and multi‐physics process simulation was proposed to develop a resin transfer molding (RTM) process for an aircraft wing flap composite part. Initially, RTM6 resin was thermally characterized using differential scanning calorimetry and curing kinetics was modeled using Kamal and Sourour model. A multi‐physics approach was employed to simulate the RTM mold filling and curing phases. Mold filling simulations were performed to obtain an effective injection strategy for the composite part. One‐point injection port and five‐point vents were obtained as an effective injection strategy using a trial and improvement process. Curing simulations were performed on the composite part using neat resin cure kinetics and cure process windows for neat resin and composite panel were developed. Subsequently, a cure difference window was developed to investigate cure difference progression between neat resin and composite panel at the processing conditions. Finally, the kinetics of cure difference progression was modeled as a function of neat resin cure conversion to design operable cure cycles for the composite panel. The results found that the cure differences converge with the increase in applied mold temperature. [ABSTRACT FROM AUTHOR]

Thermoplastic Resin Transfer Molding can be used to produce polyamide 6‐based composites from ε‐caprolactam by anionic ring‐opening polymerization. However, the service life and applicability of these composites are limited because polyamide 6 is sensitive to UV radiation. Therefore, we analyzed the effect of nanosized titanium dioxide on the UV stability of polyamide 6 produced from ε‐caprolactam. Despite the very low viscosity of caprolactam, we dispersed nanoparticles homogeneously in it before producing polyamide 6 from it. We have shown that both structural and chemical changes occur in the material under UV exposure. We proved that UV irradiation increases the crystalline fraction of the samples. This is caused by the shortening of the polymer chains. The crystalline fraction increases less with the addition of TiO2, which shows its UV protective effect. The particles prevent the rays from reaching the inside of the sample, producing a chalking effect on the surface. We analyzed and proved the chemical change in the samples by FTIR and color measurement. Our results showed that surface‐treated titanium dioxide was more stable, and the ideal filler content was about 0.6 w/w%, above which photodegradation accelerated. This can be attributed to the photocatalytic activity of the titanium dioxide particles. [ABSTRACT FROM AUTHOR]

This article has experimentally and numerically investigated the high‐velocity impact resistance of the composite sandwich panel with an M‐shaped lattice core reinforced by nano‐SiO2. For this purpose, firstly, a glass fiber resin epoxy sandwich panel has been fabricated in the laboratory. In this regard, the vacuum‐assisted resin transfer molding (VARTM) method has been used to achieve a laminate without any fault. In order to improve the impact resistance of the composite, the nano‐SiO2 were added to the resin epoxy matrix as filler with the ratios of 1%, 2%, and 3% of the composite's total weight. A scanning electron microscope (SEM) has been utilized to observe the microscopic structure of the composites, and it shows an exceptional homogeneous mixture of nano‐SiO2 particles in the resin epoxy matrix. From the experiment results, it was figured out that by adding 1 to 3 wt% of nano‐SiO2 into the composite, the output velocity of the projectile decreases. On the other hand, the results showed that when the projectile collides with the core of the sandwich panel, it remains in the sandwich panel and its output velocity will be zero. However, when the projectile does not completely collide with the core, the output velocity of the projectile will not be zero. In order to validate the results, a finite element analysis (FEA) has been developed to simulate the high‐velocity impact test. Then the experimental data has been compared to numerical simulation and good agreement was observed. [ABSTRACT FROM AUTHOR]

This paper prepares a flexible MXene/CNT film by layer‐by‐layer (LbL) self‐assembly process. Based on excellent conductivity and good compatibility with resin, MXene/CNT can be used for on‐line monitoring of large and complex liquid composite molding (LCM). In this paper, the MXene/CNT will be used as a novel micro‐nano sensor. The MXene/CNT sensor is embedded between the sandwich layers of the sandwich composite structure. The resistance information of the MXene/CNT sensor was collected by online monitoring system during LCM. The tube cross‐linked network's conductive model will be established to reveal the resistance response sensing mechanisms of MXene/CNT sensors and the response rules of resin flow states and resistance signals. Using the real‐time monitoring information collected by the MXene/CNT sensor, combined with Darcy's law, the comparison results of different permeability are obtained. The monitoring results show that polyvinyl chloride (PVC) interlayer significantly influences the resin flow trend and penetration of the core layer. Simultaneously, the interlayer's presence will also affect the resin flow trend and penetration of the lower layer of the PVC sandwich layer. The research results will provide theoretical guidance and technical support for designing process parameters and in situ real‐time monitoring of LCM in the engineering industry. [ABSTRACT FROM AUTHOR]

The halogen‐free flame‐retardant continuous glass fiber/polyamide 6 (GF/PA6) composites containing hexaphenoxycyclotriphosphazene (HPCTP) were prepared by the resin transfer molding (RTM) process. The influence of HPCTP content on mechanical properties of GF/PA6 composites was studied. The addition of HPCTP has no obvious effect on the tensile properties of composites, and the tensile strength of GF/PA6 composites with the addition of 30% HPCTP reaches 425.2 MPa. However, with the addition of HPCTP, the flexural strength and interlaminar shear strength of GF/PA6/30%HPCTP composites decrease to 246.4 and 20.9 MPa, respectively. The flame retardancy, thermal stability, and burning behavior of the composites were evaluated by means of limited oxygen index (LOI), UL‐94, thermogravimetric analysis and cone calorimeter. The results show that the LOI value of GF/PA6 composites can reach up to 30.9% corresponding to the grade of UL‐94V‐0 with the addition of 30% HPCTP. The flame retardancy mechanism of GF/PA6/30%HPCTP composites is attributed to the combined effects of releasing incombustible gases in gas phase at the early stage and forming char layers in the condensed phase, which can dilute the concentration of combustible gas and retard the mass and heat transfer. [ABSTRACT FROM AUTHOR]

The creation of Koji Pottery art is a creative act that has risen rapidly in recent years. The difference in the proportion of ingredients in the glaze directly affects the roughness, luster, and glaze of the glazed surface of the work. The curve of heating and cooling is also the key to the success or failure of the work. Therefore, taking the Koji tea bowl shape as a research example, a virtual reality simulation system and an OSG (OpenSceneGraph) artificial intelligence platform are used to construct a Koji tea bowl shape simulation model, and then the physical production is performed according to the model. After the design and production of the Koji tea bowl shape, the RTM (resin transfer molding) model is used to evaluate the process quality standard requirements of the Koji bowl shape. According to the RTM model test results, the homogeneity test results show that the result is much larger than 0.10, from which it can be inferred that the Koji tea bowl shape has reached the national process quality standard requirements. At the same time, the OSG artificial intelligence platform uses the iterative random sampling method to extract and display the abnormal data in the simulation model, which greatly improves the success rate of ceramic creation. In this paper, the creation and simulation of virtual ceramics based on OSG artificial intelligence platform are deeply studied and analyzed, and the related processes are improved, which reduces the difficulty of software operation and improves the creation efficiency. [ABSTRACT FROM AUTHOR]

This article investigates the effect of fabrication techniques on the physical, mechanical, and erosion wear properties of glass fiber reinforced dolomite dust‐filled epoxy composites. The composites were fabricated by hand layup and vacuum‐assisted resin transfer molding (VRTM) techniques with fixed glass fiber (20 wt%) and varying dolomite dust (0 to 15 wt%) with epoxy resin. In physical properties, the experimental density consistently increased with the increase in the dolomite hand layup and the VRTM process; in opposite the voids content increased in the hand layup process and decreased in the VRTM process. In mechanical properties, the hardness, impact energy, and interlaminar shear strength increases while tensile and flexural strength consistently decreases with dolomite dust content. Using Taguchi's optimization technique, the erosion wear of the fabricated composites was also evaluated at different impingement angles, impact velocities, and erodent sizes. Erosion test results indicate that the VRTM process fabricated composite has minimum erosion wear compared to the hand layup process. The eroded surfaces were studied using a scanning electron microscope to understand the erosion behavior of particulate‐filled fiber reinforced polymer composites. [ABSTRACT FROM AUTHOR]

Present article has experimentally determined the flexural strength of carbon fiber reinforced polymer sandwich panel reinforced by nano‐SiO2 with novel M‐shaped lattice core. For this purpose, a polymer composite sandwich panel with M‐shaped core made of carbon‐epoxy fiber has been fabricated in this experiment. In order to fabricate the sandwich panels, the vacuum assisted resin transfer molding has been used to achieve a laminate without any fault. Afterward, polyurethane foam (PU) has been injected into the core of the sandwich panel. In order to determine the flexural strength of the sandwich panels, they have been subjected to three‐point bending loads. From the results of the study, it was figured out that: a) Adding 1 to 3 wt% of nano‐SiO2 into the carbon fiber had the most desirable effects on the enhancement of flexural strength of the sandwich panels. b) PU has improved the flexural strength of sandwich panels. c) The new M‐shaped core can well postpone the buckling and failure of the composite sandwich structures. [ABSTRACT FROM AUTHOR]

Present article has experimentally determined the flexural strength of carbon fiber reinforced polymer sandwich panel reinforced by nano‐SiO2 with novel M‐shaped lattice core. For this purpose, a polymer composite sandwich panel with M‐shaped core made of carbon‐epoxy fiber has been fabricated in this experiment. In order to fabricate the sandwich panels, the vacuum assisted resin transfer molding has been used to achieve a laminate without any fault. Afterward, polyurethane foam (PU) has been injected into the core of the sandwich panel. In order to determine the flexural strength of the sandwich panels, they have been subjected to three‐point bending loads. From the results of the study, it was figured out that: a) Adding 1 to 3 wt% of nano‐SiO2 into the carbon fiber had the most desirable effects on the enhancement of flexural strength of the sandwich panels. b) PU has improved the flexural strength of sandwich panels. c) The new M‐shaped core can well postpone the buckling and failure of the composite sandwich structures. [ABSTRACT FROM AUTHOR]