Applied Composite Materials最新文献

Traditional cellulose-based paper suffers from inherent flammability, hydrophilicity, and oxidative degradation. These limitations cause irreversible damage, including yellowing, moisture absorption, and structural decay, during long-term archival storage. To address these challenges, a biomimetic strategy inspired by the hierarchical architecture of bird-nest (interwoven branches, grass, and mud) is proposed to engineer a multifunctional composite paper. By integrating aluminum silicate fibers (ASF) as load-bearing “branches”, ultralong hydroxyapatite nanowires (HAPNW) as flexible “grass”, and an inorganic adhesive(aluminum oxide sol) as binding “mud”, a nest-like network is constructed to synergistically enhance mechanical robustness, flame resistance, and environmental stability. Unlike pure HAPNW paper with limited tensile strength (25 MPa), the optimized composite (30% ASF) achieves a remarkable strength of 62 MPa and modulus of 9 GPa, attributed to stress redistribution via interfacial fiber entanglement and inorganic binder-mediated cohesion. Further hydrophobic modification confers superhydrophobicity and self-cleaning capabilities, while retaining writeability comparable to conventional paper. Crucially, the composite exhibits non-combustibility under direct flame exposure (700°C, 60 s) and exceptional thermal stability (84% residual mass at 800°C), outperforming commercial counterparts. This work pioneers a biomimetic paradigm for designing high-performance archival materials, offering a sustainable solution to reconcile mechanical durability, fire safety, and environmental resilience in paper-based preservation technologies.

Carbon fibre-reinforced thermoplastics used in structural applications, such as crash-relevant parts, are typically subjected to different strain rate conditions. This requires a deep understanding of their structural behaviour under these conditions. To date, there is limited data on their strain rate dependent behaviour. In this study, four-point flexure tests are used to determine the longitudinal flexural properties and failure behaviour of unidirectional carbon fibre-reinforced polyamide 6 (CF-PA6) material as a function of the applied strain rate. A universal testing machine and a drop tower test setup with two different drop heights were used to investigate the behaviour in quasi-static (1.3 × 10^− 4 1/s) to medium strain rates (7 1/s). Flexural modulus, flexural strength and fracture strain were determined for all strain rates applied, and the fracture morphology was analysed using microscopic images and high-speed camera recordings. Further, Weibull analysis was performed on the flexural strength. The experimental investigation of the flexural properties showed no significant strain rate effect and no trend was observed in the Weibull parameters. Irrespective of the strain rate applied, all specimens tested exhibited a comparable fracture morphology due to a similar failure process of initial compressive failure followed by tensile failure.

SiCp/Al composites, with high specific strength, low thermal expansion coefficient, and excellent wear resistance, are widely used in aerospace lightweight components. However, during machining, hard and brittle SiC particles not only accelerate tool wear but also restrict low-damage machining efficiency due to complex chip formation mechanisms and uncontrollable surface damage. Thus, focusing on low-volume-fraction SiCp/Al, this study investigates the chip formation mechanism and its impact on surface morphology, revealing how cutting parameters regulate chip morphology and surface quality to provide theoretical support for process optimization. A three-phase SiCp/Al thermo-mechanical coupling model was built, combined with 2D cutting simulations to analyse the mesoscopic mechanism of chip formation, validated via single-factor cutting experiments. Scanning electron microscopy (SEM) and image processing techniques were used to characterize chip morphology and geometric features, and the mapping relationship between cutting parameters, chip morphology, and surface damage was established. Findings show that serrated chips are easily formed during SiCp/Al cutting; the shape and distribution of SiC particles are key factors regulating chip and surface morphology, with a 6.31% error between simulation and experimental results. With increased cutting speed, chip serration intensifies; enhanced plastic flow of the aluminium matrix drives serrations to evolve into continuous shear flow, with simultaneous improvement in surface quality. As cutting depth increases, chip serration also rises; however, intensified stress concentration in the cutting zone leads to coarser serrations, along with more microcracks, particle pull-outs, and pits, causing a continuous increase in surface roughness. Optimizing cutting parameters can balance chip stability and workpiece surface integrity, providing a process basis for efficient, low-damage machining of SiCp/Al components.

Phenolic resin-impregnated aramid paper honeycombs are promising for engineering applications. However, most designs cannot provide sufficient load-bearing capacity, limiting their application as structural materials. Here, a novel re-entrant honeycomb structure is designed based on the expansion manufacturing method and 17 distinct honeycomb structures are derived from this structure using the Box-Behnken design method. Compression tests are performed on the re-entrant honeycomb to investigate its deformation mechanism and validate the finite element model. Numerical results from 17 honeycomb structures demonstrate that peak stress, plateau stress and energy absorption increase with increasing density and total side length, while decreasing with increasing angle of 1/4 unit cell. The analysis of collapse mechanisms reveal that the plastic deformation mode comprised both bending and membrane deformations. On this basis, an analytical model for predicting the mean compressive strength of honeycomb structures is developed using a simplified super folding element theory. The theoretical solution is in good agreement with the simulations. Furthermore, a multiobjective optimization method is used to efficiently optimize the structural parameters, resulting in the acquisition of optimal structural parameters that meet the load-bearing requirements. The yield strength, mean compressive strength and energy absorption of novel honeycomb are significantly higher than other popular honeycomb structures.

This study prepared three-dimensional orthogonal jute/basalt composites with varying weft mixing ratios via vacuum-assisted resin transfer molding (VARTM). The composites were subsequently immersed in distilled water at two temperatures (25 °C and 65 °C) for up to 90 days.Moisture absorption tests and low-velocity impact (LVI) tests were performed on hygrothermal-treated composites, with damage morphologies characterized using optical microscopy and scanning electron microscopy (SEM). Results showed that moisture absorption rate of composites increased with jute content. Among all specimens, the pure jute composite specimen ([7J]) showed the highest moisture absorption rate, while the pure basalt composite specimen ([7B]) demonstrated the lowest. Elevated temperature accelerated moisture diffusion and matrix degradation, while fiber arrangement also affected moisture absorption performance. Hygrothermal aging degraded LVI performance: after 90-day aging at 65 °C, peak load of the jute/basalt weft-alternating hybrid composite specimen ([4B3J]) specimens decreased by 38.01% and energy absorption reduced by 24%, attributed to matrix hydrolysis, fiber-matrix interface debonding, and microcrack propagation. Damage analysis revealed that specimens with higher jute content experienced more severe fracture and delamination, with aging exacerbating the “I”-shaped back surface damage. This study provides theoretical guidance for engineering applications of natural fiber hybrid composites in hygrothermal environments.

This study investigated impact damage characterization of reinforced thermoplastic pipes (RTP) using X-ray computed tomography (CT) scan and phased array ultrasonic testing (PAUT) techniques. Two types of RTP samples, namely the standard (ST) and gas-tight (GT) types, were impacted using a drop-weight tower. The X-ray CT scan revealed detailed cross-sectional views of damages, including fiber breakage, matrix degradation, and aluminum layer damage. With the implementation of time-corrected gain method in a zero-degree configuration, PAUT demonstrated damage detection capabilities comparable to the CT scan technique by employing various frequencies and focusing techniques. However, it was challenging to accurately assess the extent of damage in the GT type due to the presence of the aluminum layer. While higher-frequency PAUT transducers improved sizing accuracy for the ST type, sizing damages in the GT type remained challenging. Implementing a focusing technique revealed ultrasonic B-scan cross-sectional images of damage closely resembling those from CT scans, offering insights into through-thickness damage morphology. This research showed that the results from the ultrasonic wave-based technique were in good agreement with those from the X-ray imaging-based technique.

Dynamic axial crushing tests were performed on C-section carbon fiber reinforced polymer (CFRP) composite stanchions used in sub-cargo area of aircraft to evaluate their dynamic response under high-speed axial crushing load. A numerical model based on the continuum damage mechanics (CDM) was developed, with calculated failure modes and crushing loads closely matching experimental results, validating the model’s accuracy and reliability. The influence of equivalent axial stiffness and lay-up sequence on the crushing failure modes and energy absorption characteristics of the stanchions was investigated. A mathematical relationship among the specific energy absorption (SEA), average crushing load and equivalent axial stiffness was fitted. The results showed that, compared to single lay-ups, hybrid lay-up configurations exhibited superior structural stability and energy absorption performance. In particular, lay-up configurations with higher equivalent axial stiffness significantly enhanced both the SEA and average crushing load. Furthermore, when the equivalent axial stiffness was held constant, variations in lay-up sequence had a relatively minor effect on the energy absorption characteristics. However, if the axial stiffness of the outermost plies was significantly reduced by consecutively placing 90° plies on the outermost plies, the axial stability of the stanchion deteriorated rapidly, leading to a pronounced decrease in its energy absorption performance.

Honeycomb structures have garnered significant attention due to their outstanding mechanical properties, including high strength, high stiffness, and excellent energy absorption capabilities. This paper innovatively incorporates circular arcs and support structures based on the configuration characteristics of positive and negative Poisson’s ratio cells, designing three novel circular arc honeycomb configurations and their combination forms. Specimens were fabricated using FDM technology. Through uniaxial compression and three-point bending tests, the quasi-static compression and bending properties of these structures were systematically investigated. Finite element simulations provided in-depth insights into deformation mechanisms and stress evolution during compression. Results indicate that the negative Poisson’s ratio with arc and support structure exhibits superior compressive performance, achieving a compressive ultimate strength of 2.6 MPa and a specific energy absorption of 3815.9 J/kg. Compared to conventional honeycomb structures, the specific energy absorption value increased by 3.15 times. Finite element analysis indicates that the arc design effectively disperses stress and enables stable progressive folding. With its high specific strength (6.9 MPa·cm³/g), the negative Poisson’s ratio structure with arcs is suitable for lightweight applications. Bending test results show that the positive Poisson’s ratio arc structure exhibits the highest average crush force (249.1 N) and specific energy absorption (158.8 J/kg) due to arc-induced shear stress dispersion. Combining the three unit cells enhances the mechanical properties of individual cells, with the failure sequence of the composite structure following the strength gradient of the unit cells. This study achieves synergistic optimization of lightweighting, load-bearing, and energy-absorption performance through structural innovation combined with additive manufacturing technology. It provides valuable reference for structural design and application in aerospace, transportation, and building protection fields.

This work examines the joining performance of metal-polymer composite single-lap joints (SLJs) enhanced with 316 L stainless steel Z-pins manufactured through fused filament fabrication (FFF). The Z-pin arrays and steel substrates were co-printed using FFF, and then subjected to debinding and sintering processes. The resulting structure was subsequently combined with polyphenylene sulfide (PPS) through an injection molding direct joining (IMDJ) process to create durable 316 L-PPS composite SLJs. The results show that incorporating FFF-fabricated Z-pins significantly enhance the joining performance of metal-polymer SLJs. A detailed investigation into the effects of pinning density and Z-pin alignment on polymer melt behavior and joint performance revealed that higher pinning densities and vertically aligned Z-pins (90° angle) resulted in superior joint strength. This configuration enhanced PPS melt flow, minimized interfacial defects, and achieved the highest shear strength—improving by up to 113.1% compared to unreinforced joints. The improved mechanical response is primarily due to the Z-pins’ ability to dissipate energy through mechanisms such as interfacial sliding and localized deformation, which hinder crack initiation and growth. This study presents a distinctive strategy for engineering metal-polymer composite joints, enabling the fabrication of multifunctional hybrid structures with enhanced performance.

Conventional honeycomb structures face problems of local buckling, brittle fracture, and insufficient energy absorption efficiency under out-of-plane compression. To address these limitations, this study investigates a bio-inspired spiderweb-like honeycomb structure using 3D-printed short carbon fiber reinforced nylon composite. Specimens of spiderweb-like and conventional hexagonal honeycomb structures were fabricated via fused deposition modeling technology. Through quasi-static compression tests and finite element simulation, deformation modes and energy absorption characteristics of different honeycomb structures were comparatively analyzed. Results demonstrate that the spiderweb-type honeycomb structure achieves significant improvements in load-bearing capacity and energy absorption efficiency through hierarchical collapse mechanisms and coordinated deformation of multiple plastic hinges. Compared to conventional hexagonal honeycombs with equivalent wall thickness, the spiderweb structure exhibits 221% greater load bearing capacity and 94% higher specific energy absorption. When compared to conventional hexagonal honeycomb structures with the same area density, the spiderweb honeycomb shows a specific energy absorption increase of about 35% and a total energy absorption increase of 93.9%. Additionally, parametric studies reveal that hierarchical design parameters r (the ratio of the side lengths of the inner and outer honeycomb layers) in the spiderweb structure plays an important role in the distribution of plastic hinges and plateau stress. When r is in the range of 0.4 to 0.6, the structure achieves uniform stress distribution and maintains high load-bearing capacity through anti-symmetric buckling and progressive folding deformation. However, when r = 1 or r < 0.4, the structure undergoes global buckling or brittle fracture, leading to a decrease in energy absorption performance. This work develops a design framework for bio-inspired hierarchical composites with tailored energy absorption performance, demonstrating specific parameter configurations that achieve superior energy absorption for aerospace and automotive applications.