Applied Composite Materials最新文献

This study examines the flexural performance and damage evolution in multiscale graphene nanoplatelet-reinforced fiber metal laminates (FMLs). A multiscale modeling framework was developed to analyze the material’s mechanical response. At the mesoscale, a periodic representative volume element (RVE) approach was applied to carbon fiber/epoxy hybrid regions, enabling the calculation of homogenized mechanical properties for these composite layers. At the macroscale, simulations replicated the FMLs’ layered architecture through a unified framework integrating three material behavior laws: the Johnson-Cook model to describe aluminum sheet plasticity and damage, the three-dimensional Hashin criterion to predict failure in carbon fiber/epoxy layers, and a cohesive zone model to simulate interfacial debonding between the metal and composite phases. Experimental investigations employed quasi-static three-point bending tests to evaluate deformation and failure mechanisms in autoclave-processed FMLs reinforced with graphene. Finite element simulations corroborated experimental observations, elucidating stress distribution and progressive damage across material layers through force-displacement curves and damage propagation maps. Microscopic analysis via scanning electron microscopy (SEM) further revealed the role of graphene nanoplatelets in enhancing resin-aluminum interfacial adhesion and mitigating delamination. The proposed method is also applicable to the modification of FMLs using other types of nanofillers.

Internal thermal expansion molding is a cost-effective composite fabrication technique that enables the integrated formation of complex, enclosed structures. In sandwich structures, interfacial delamination critically affects bearing capacity, making interface performance a key concern. Thus, this study primarily focuses on integrated multilayer sandwich structures to investigate the mechanism of mode I interfacial fracture toughness. The research findings firstly demonstrate that the expansion ratio (ER) systematically influences various parameters, including compliance, delamination length, fracture propagation mode, and final loading. The interface between carbon fiber reinforced polymer (CFRP) and thermal expansion foam (TEF) (C-T interface) exhibits an initial fracture toughness of ~ 0.53 kJ/m², which exceeds the TEF itself by ~ 235.7%. Similarly, the interface between polymethacrylimide (PMI) and TEF (P-T interface) achieves a synergistic enhancement, with interfacial toughness surpassing that of the individual base materials. These improvements are attributed to co-curing-induced bonding, increased interfacial contact, reduced thermal stress, the formation of mechanical interlocks, and mitigation of stress concentrations. The results demonstrate that the integrated multilayer sandwich composite structures fabricated via the internal thermal expansion technique not only enable efficient, integrated manufacturing, but also achieve superior interfacial properties relative to traditional three-layer structures.

Double-Double (DD) laminates have attracted growing interest because of their design flexibility and the potential to reduce ply count while maintaining stiffness; however, their performance under repeated impacts and the ensuing residual compressive strength (RCS) remain insufficiently understood. In this work, a DD laminate with the stacking sequence (:{left[52/-32/-52/32right]}_{4T}) was configured to match the bending stiffness of a Quadriaxial (Quad) laminate, (:{left[{-45}_{2}/{45}_{2}/{0}_{2}/{90}_{2}right]}_{s}). A finite element framework—previously validated against low-velocity impact (LVI) experiments—was employed to simulate two successive same-site impacts with energies of 5, 15, and 25 J, followed by compression after impact (CAI) loading to determine RCS. Results show that the DD laminate better preserves global structural integrity; however, once damage is initiated, its severity exceeds that of the Quad laminate at the same impact energy. Under otherwise identical conditions, the delamination damage projected area (DDPA) in the DD laminate is 30.01–53.45% smaller than that of the Quad, and during the second impact, the delamination preferentially propagates through the thickness rather than in-plane. CAI analyses further indicate that the DD laminate accumulates less matrix compressive damage than the Quad. For the pristine DD laminate, compressive failure is governed by the combined action of delamination initiated under load and fiber compression damage, whereas in the impacted DD laminate it is dominated by delamination. The second impact does not alter the failure mode. Under the same conditions, the DD laminate achieves an RCS 6.17–23.80% higher than that of the Quad, and the second impact reduces RCS by less than 10%. These findings provide a reference for evaluating secondary impact response and RCS of DD laminates.

This study presents a novel methodology for the multi-objective parametric optimization of a non-symmetrical filament-wound composite vessel subjected to thermo-mechanical loading. Due to the vessel’s unequal polar openings, a nonuniform fiber angle distribution is required along the cylindrical section. The proposed approach incorporates both geodesic and non-geodesic fiber paths, accommodating the asymmetry in polar openings through cross-linear modeling of the helical layers across the domes and the cylindrical region. To achieve an innovative and weight-efficient design, a multi-objective optimization problem was formulated. The optimal radii of the polar openings and the composite layer thicknesses were determined to enhance the vessel’s thermomechanical performance. Thermal loading, particularly at high operating temperatures, is identified as a critical factor due to its potential to induce structural degradation. A specialized iterative algorithm was developed to perform the optimization, integrating an improved thermomechanical module, an optimization module, and a custom Python script. The Multi-Island Genetic Algorithm (MIGA) was employed to solve the optimization problem. Test cases were evaluated using two commercially available composite materials. Compared to purely mechanical models, the thermo-mechanical model can optimize material usage by approximately 10%.

This study investigates the mechanical properties and failure characteristics of CFRPs fabricated with thermoplastic resins—polypropylene (PP) and polyamide 6 (PA6)—through a newly proposed experimental approach, in which the failure process was systematically examined from initial loading to the final failure mode. The CFRPs, composed of carbon fibers embedded in the respective resin matrices, were produced under varying molding pressures. The mechanical properties of CFRP-PP and CFRP-PA6 show clear distinctions. The bending strength of CFRP-PA6 reached approximately 1,200 MPa, which is about 20% higher than that of CFRP-PP (1,000 MPa). Moreover, their post-peak responses exhibited distinct differences. At the ultimate bending strength point (σ_b), the bending stress experienced a sharp drop (σ_d), followed by a recovery phase that varied depending on the resin type. Specifically, CFRP-PA6 demonstrated a noticeable stress recovery, whereas CFRP-PP showed a continued decline. Moreover, CFRPs molded under higher pressures exhibited more pronounced stress recovery in both resin systems. SEM analyses revealed distinct failure mechanisms. At the σ_b point, CFRP-PA6 showed no clear evidence of failure, while CFRP-PP displayed a combination of fiber breakage and delamination. At the σ_d and the final fracture points, CFRP-PA6 exhibited relatively weak failure, primarily characterized by fiber breakage and localized strain distortion, whereas CFRP-PP suffered severe fiber breakage and extensive delamination. These differences in failure modes are attributed to variations in interfacial bonding strength between the carbon fibers and the resin matrices. Bonding tests confirmed that CFRP-PA6 possesses superior adhesion and wettability to carbon fibers compared to CFRP-PP.

Using fibre reinforced polymer (FRP) to confine reinforced concrete columns is a commonly employed method for strengthening in civil engineering. Columns are essential load-bearing elements, and their failure can result in a disastrous collapse of the structure. The aim of this study is to address a deficiency in the current body of knowledge by conducting a comprehensive examination of the application of carbon fibre-reinforced polymer (CFRP) and aramid fibre-reinforced polymer (AFRP) composite as a material for retrofitting. This study investigates the influence of the quantity of CFRP layers and the incorporation of aramid fibres as retrofitting elements on improving blast resistance. Experimental results presented by Yan et al. (2020) consisting of 12 columns with varying thicknesses and strengthening were validated using the finite element tool LS DYNA. The numerical modelling results showed that using CFRP reinforcement improved the ability to withstand damage, leading to a decrease in residual displacement. Verified numerical models are utilised to conduct parametric analysis on the impact of aramid fibre reinforcement polymer (AFRP) on mid-plane displacement and internal energy absorption. The results suggested that AFRP exhibit greater resistance to blast loads as compared to CFRP.

In this paper, we use numerical modeling to predict the effective electrical conductivity of Carbon-Black/Ultra-High-Molecular-Weight-Polyethylene (CB/UHMWPE) nanocomposites. The models are based on the microstructure observed in X-ray microcomputed tomography (μCT) scans. For the examined range of carbon black weight fraction, the scans demonstrate conductive CB particles to be agglomerated around the UHMWPE granules, creating CB-containing layers surrounding the granules and forming electrically conductive network. First, the generalized effective medium (GEM) method is considered as an analytical tool to predict the overall conductivity based on the volume fraction of conductive inclusions. The applicability of this method for the observed microstructure with conductive layers is discussed. Then, an alternative two-stage approach based on a combination of numerical and analytical modeling is proposed. Finite element models of representative volume elements (RVEs), incorporating the CB-containing layers, are developed. It is shown that the GEM parameters of the CB-layers can be determined by the comparison of the numerical modeling results with the experimental measurements of the overall composite conductivity.

This study examines the influence of yarn breakage, specifically the number of layers and their location, on the low-velocity impact response and post-impact compression performance of 3D woven composites. Specimens with yarn breakage on either the upper or lower surface were impacted at two different energy levels. Damage evaluation was conducted using C-scan, μ-CT, and DIC methods. The results indicate that yarn breakage on the lower surface (tension zone) leads to notable reductions in initial stiffness (up to 40.2%) and peak load (up to 33.4%), with a clear threshold effect when two or more layers are broken. This condition also resulted in significantly expanded damage area (up to 94.3% increase). In contrast, breakage on the upper surface (compression zone) mainly increased energy absorption (up to 84.4%) and permanent displacement (up to 65%) under high-energy impact. Additionally, compression-after-impact strength was approximately 11% lower for specimens with yarn breakage on the lower surface, where failure was governed by a damage network initiated by the yarn breakage. These findings provide concrete design guidelines for avoiding critical strength reduction and optimizing damage tolerance in composite structures containing yarn breakage defects, particularly for aerospace applications where impact resistance is crucial.

Honeycomb structures are widely used in buffering, protective systems, and impact-related applications due to their lightweight, high strength, and excellent energy absorption capabilities. However, conventional honeycomb designs often suffer from limited load-bearing capacity, single-stage collapse behavior, and insufficient energy absorption efficiency, making them inadequate for high-performance energy-absorbing systems. To address these limitations, this study proposes a novel Framed Diamond-Star Honeycomb (FDSH) structure with a dual-plateau response. The mechanical performance and energy absorption characteristics of the proposed structure were systematically investigated through quasi-static compression experiments and finite element simulations. The effects of key geometric parameters, including cell angles and wall thickness, were also analyzed. The results show that the FDSH structure exhibits a distinct dual-plateau behavior during compression and achieves significant improvements in specific energy absorption—by approximately 238.18% and 161.97%—compared to traditional star-shaped honeycombs (SSH) and re-entrant hexagonal honeycombs (REH), respectively. Furthermore, parametric studies confirm that geometric parameters have a significant influence on plateau stability and energy absorption performance.

Compared to conventional honeycomb structures with a positive Poisson’s ratio, negative Poisson’s ratio (NPR) structures exhibit greater densification strain under impact, enabling more efficient energy absorption. Based on this principle, a novel cuttlebone-inspired multi-circular arc core (MCAC) structure is proposed, exhibiting NPR behavior and an enhanced energy absorption (EA) capacity. Furthermore, multilevel designs (2-level, 4-level, and 6-level) were developed based on the MCAC unit to explore hierarchical structural advantages. The results demonstrate that the proposed MCAC honeycomb achieves a 30% higher stress plateau and a 36.6% increase in EA compared to a conventional star-shaped honeycomb of equal size, with a notable improvement in in-plane performance. Under a 1 J impact load, EA increases by 11.12% as core levels increase from 2 to 6; however, this trend reverses at higher impact energies. Parametric studies reveal that the large arc centroid angle θ_R significantly influences EA, yielding a 7.05% improvement in the 6-level design. These findings suggest that the MCAC design offers a promising solution for vehicle energy-absorbing box (EAB) applications.