Resin Transfer Moulding (RTM) is widely used to manufacture high-quality CFRP components for aerospace applications. Recently, a novel gapped unidirectional (UD) carbon fibre material has been developed, offering new opportunities for composite design and manufacturing. However, the damage mechanisms and defect sensitivity of RTM-manufactured laminates based on this material system remain largely unexplored. The novelty of this work lies in the investigation of damage initiation, propagation, and compressive performance in RTM-manufactured laminates produced from this newly developed gapped UD material, with particular emphasis on the role of manufacturing-induced defects. Thin Teflon films were embedded at the laminate mid-plane to introduce controlled artificial delaminations, enabling a systematic assessment of their influence on damage initiation, damage propagation, and interlaminar stress redistribution. Progressive tensile and compressive testing, combined with stepwise microscopic inspection, was employed to track damage evolution. The results showed that crack initiation under tensile loading is governed primarily by ply orientation, with matrix cracks consistently initiating in the central 90° plies at strains of 0.4–0.5
Carbon fiber reinforced polymer (CFRP) and titanium alloy (Ti) stacked structures are widely used in high-end equipment fields, but significant differences in anisotropy, brittleness, and ductility between the two materials cause complex stress concentration and progressive damage around bolt holes. Current research mainly focuses on ultimate capacity and final failure, while systematic comparisons of hole‑wall displacement, local equivalent contact stress in different ply groups, and damage propagation paths due to varying bolt numbers remain insufficient. Therefore, quasi‑static tensile tests with a progressive damage model based on the modified 3D Hashin criterion is combined, then single‑ and double‑bolt CFRP/Ti joints are compared in terms of load‑displacement response, hole‑wall local response, and damage evolution. Results show both joints exhibit a four‑stage load‑displacement curve. In the single‑bolt joint, load concentrates on a single hole wall, damage initiates in lower plies and propagates perpendicular to loading, leading to splitting failure. In the double‑bolt joint, an additional path through both holes and the ligament forms, with more severe damage around the loading‑end hole and an oblique damage band. Evolution of local equivalent contact stress in different ply groups further indicates stress release and re‑concentration in the single‑bolt joint, while the double‑bolt joint shows sustained bearing. This study reveals the effect of bolt number on local load transfer and failure modes from hole‑wall displacement and contact stress evolution, providing a design basis for inter‑hole bearing regions in CFRP/Ti joints.
Carbon fiber-reinforced rubber matrix composites (CFR-RMC) exhibit excellent deformability, elastic recovery, and ablation resistance, enabling them to overcome the deformation limitations of rigid thermal protection materials. However, reliable predictive models for their thermo-chemo-mechanical coupled response under high-temperature ablation remain lacking. The novelty of this paper lies in constructing a fully coupled thermo-chemical–mechanical framework that links pyrolysis kinetics, temperature- and carbonization-dependent properties, and mechanical equilibrium for isotropic short CFR-RMC. The model framework was validated using measured back temperatures as well as the total deformation induced by ablation and thermal expansion, achieving relative errors below 0.46
Accurate characterization of the 3D fiber network in Short Fiber Reinforced Polymer composites (SFRPs) is critical for predicting material performance. However, existing commercial tools often struggle with “erroneous agglomeration” when processing conventional-resolution micro-computed tomography (µCT) data, leading to physically implausible fiber length distributions. This study presents a highly automated, lightweight analysis pipeline that integrates machine learning-based segmentation with a novel topology-aware morphological post-processing algorithm. The proposed method was validated on PA66-GF30 datasets at both high (1 μm/voxel) and conventional (3 μm/voxel) resolutions. At high resolution, the proposed pipeline produced Fiber Orientation Distributions (FOD) that were highly consistent with those obtained using industry-standard software (Avizo), with Pearson correlation coefficients greater than 0.93. At conventional resolution, where commercial software showed severe over-agglomeration, the proposed pipeline produced a fiber length distribution within a physically reasonable range (predominantly 30–450 μm), which was consistent with the high-resolution reference dataset. Furthermore, an adaptive tiling strategy enables the efficient processing of billion-voxel datasets on a standard 16GB laptop in approximately 45 min, a task that typically causes memory failure in standard commercial software. This work provides an automated and computationally accessible pipeline for high-throughput microstructural analysis of SFRPs.
To address the difficulty in directly measuring constituent properties, this study explores a closed-loop inverse identification framework based on micromechanics. The framework first inversely determines the elastic constants of fibers, and then performs micromechanical analysis on a hexagonal representative volume element (RVE) to obtain both the homogenized macroscopic constants and stress amplification factors (SAFs). The homogenized macroscopic constants are employed in numerical modeling of open-hole laminates, whereas the SAFs are incorporated into the constituent failure criteria to inversely derive the tensile and compressive strengths of the fiber and the matrix. Subsequently, the inversely obtained constituent strengths are applied to material points at the stress concentration regions around the hole edges of open-hole laminates to predict the macroscopic laminate strength. Comparison with experimental results showed that the maximum prediction deviation across all test cases was 15.7
Composite materials undergo complex physicochemical transformations under laser irradiation, and their damage evolution laws have not been fully clarified. In this work, experiments and numerical simulations are integrated to investigate the laser ablation features of carbon fiber-reinforced polymer (CFRP) laminates under three spot diameters (6 mm, 8 mm, and 10 mm). The prominent regulating effect of air mass transfer efficiency on temperature responses and the staged evolution of ablation flames are clarified. Scanning electron microscopy (SEM) and energy-dispersive spectrometry (EDS) are employed to characterize macroscopic and microscopic morphologies of damaged zones, revealing the intrinsic thermal damage mechanism induced by laser irradiation. Experimental results show that as the spot diameter increases, the laser penetration time increases from 2.97 s to 7.34 s, accompanied by an increase in mass loss from 1.113 g to 1.232 g. The width of the heat-affected zone (HAZ) and upper-surface ablation hole diameter both increase monotonically, while the corresponding parameters on the lower surface first increase and then decrease, peaking at the 8 mm spot size. The finite element damage model developed in this study produces prediction errors below 8.5
Carbon fiber self-resistance electric (SRE) heating technology generates joule heat by passing an electric current through the carbon fibers, and leveraging its “inside-out” heating characteristic, demonstrates significant advantages of high efficiency and low energy consumption in the efficient forming of thermoplastic composites. Due to the high viscosity of thermoplastic resins and the complexity of continuous fiber architectures, single-scale modeling approaches are insufficient to accurately capture resin flow and impregnation during injection compression molding with SRE heating technology. To address this challenge, a multiscale modeling approach was employed to analyze the resin flow and impregnation behavior in the fiber preform of carbon fiber reinforced polypropylene (CF/PP) composites during this process. In the microscale, a periodic random fiber representative volume element (RVE) model was established to determine transverse permeability. Macroscale and mesoscale simulations were applied to characterize the flow behavior and impregnation performance at different stages of the molding cycle. Moreover, the local intra-tow void area fraction was quantified from cross-sectional micrographs, showing trends consistent with the simulations. This study reveals essential mechanisms in injection compression molding with SRE heating and offers guidance for process optimization.
Unidirectional carbon fiber-reinforced composites (UD-CFRC) combine low density with excellent mechanical properties but are susceptible to manufacturing-induced micro-uncertainties, such as variations in fiber strength and spatial distribution, which can significantly affect their macroscopic properties and compromise structural reliability. In this study, two representative volume element (RVE) models are established: the UR-RVE model with uniformly distributed carbon fibers and random fiber tensile strength, and the RR-RVE model with randomly distributed carbon fibers and random fiber tensile strength. The simulation results show good agreement with experimental data, validating the accuracy of the modeling framework. Subsequently, the tensile strengths predicted by both models are statistically analyzed using six probability distributions. Goodness-of-fit tests indicate that the 3P-Weibull distribution achieves the best overall trade-off between fitting performance and model complexity. Statistical analysis indicates that the random spatial distribution of fibers has little effect on the mean tensile strength, while increasing the standard deviation by 13.77
This study investigates the fabrication, mechanical properties, and structural design of three-dimensional (3D) orthogonal woven composites through an integrated experimental and numerical approach. A high‑precision predictive representative volume element (RVE) model was developed, yielding prediction errors of only 2.78
The reformability of fiber reinforced polymer composites offers a potential pathway for reuse of manufacturing scrap and end of life laminates. In this study, a carbon fiber reinforced vitrimer epoxy composite (CFRV) was compared with a carbon fiber reinforced polyamide-6 composite (CFRTP) under controlled multi-cycle thermo-stamping conditions. Laminates were subjected to up to five reforming cycles and were evaluated using tensile testing, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The CFRV composites exhibited an initial reduction in mechanical properties after the first cycle. The tensile modulus decreased about 15 T_g ) of CFRTP and CFRV composites. TGA results showed comparable high-temperature stability across cycles for both systems, with an additional low-temperature degradation feature associated with the vitrimer chemistry. These results demonstrate that CFRV composites can tolerate repeated reshaping with limited mechanical degradation after an initial conditioning cycle, while requiring lower process energy than the thermoplastic reference under the investigated conditions.
Composite materials are increasingly used in aerospace applications due to their superior strength-to-weight ratio compared to metals. However, widespread adoption is limited by certification challenges in adhesively bonded joints. Controlling and measuring adhesive bondline thickness is crucial for improving composite bonding, as thickness directly affects joint fracture properties and structural performance. This study utilized a high-temperature (up to 180 °C) ultrasonic scanning system operating in an autoclave to collect ultrasonic time of flight (TOF) data through adhesively bonded composite panels. Machine learning techniques were implemented to account for temperature effects on TOF within the adherends and to measure the TOF in adhesive bondlines. Three experiments were conducted on aerospace-grade composite panels. The first experiment, on a single composite half-panel, showed deficiencies in scaling to bonded laminates. A second experiment revised the experimental approach and generated training data for a machine learning model, which significantly improved bondline TOF prediction accuracy from 14
Composite material structures are widely used in civil aviation, aerospace and transportation due to high specific modulus, high specific strength, corrosion resistance, and fatigue resistance. However, the composite material curing deformation is generally caused by the anisotropy, the thermochemical shrinkage of the resin, and the inconsistency of the thermal expansion coefficient between the composite material and the mold, which affects the quality and manufacturing accuracy of the structure. To address this issue, the research on the curing deformation of composite materials, based on finite element (FE) simulation technology and artificial intelligence (AI) technology, has received extensive attention. This paper provides a comprehensive review on the mechanism and influencing laws of curing deformation prediction in composite components based on FE and AI technology. Furthermore, representative control techniques are summarized, including prediction-driven mold/tooling geometry compensation and iterative optimization to achieve dimensional tolerances. Based on this, some emerging development trends for the prediction of curing deformation are proposed.
This study examines the thermal and (thermo)mechanical properties of flax twill-reinforced composites (FFRCs) with a fiber volume content of approx. 51 vol
The rapid rise of textile waste, driven by fast fashion and linear manufacturing models, poses significant environmental concerns and leads to materials loss through disposal by landfilling or incineration. This study aims to identify a suitable nonwoven composite (NCs) fabrication method using mechanically recycled synthetic textile fibres. To achieve this aim, composites were developed from a 50/50 wt
High-temperature-resistant needled C/SiC composites are critical for aerospace applications, but their mechanical properties and failure mechanisms at elevated temperatures remain insufficiently explored. This study aims to optimize the needling process parameters for spreading carbon fiber fabric/web needled felts to enhance their mechanical performance and understand their high-temperature behavior. Various needling parameters, including needling density (25–40 needles/cm²), depth (11 and 15 mm), and needle hook type (F and G), were tested. The microstructure and mechanical properties of the felts were characterized by Micro-CT, tensile, and interlaminar peel tests. On this basis, the NP-M15G felt (needling density 30–35 needles/cm², needling depth 15 mm, G-type hook needle) was selected as the preform to fabricate needled C/SiC composites via the polymer infiltration and pyrolysis (PIP) process, followed by three-point bending tests at room temperature and 1600 °C. The results show that the felt compactness, tensile strength, and interlaminar peel strength first increase and then decrease with increasing needling density. Increasing the needling depth promotes the formation of longer needled fiber bundles and improves structural compactness, thereby enhancing the overall mechanical performance. In addition, the G-type needle introduces more Z-direction fiber bundles, further improving interlaminar properties. The NP-M15Gs composite exhibits non-brittle fracture behavior at both room temperature and 1600 °C; however, the flexural strength and modulus decrease by approximately 32.49
This paper investigates the dynamic response and failure mechanism of the double-layer M-shaped foldcore sandwich structure under low-velocity impact through experimental and finite element studies. Based on the length of the single-cell sawtooth platform, three different-sized hemispherical punches were used to conduct low-velocity impact experiments on two typical positions of the structure. The experimental results indicate that the larger the punch size, the greater the average penetration resistance encountered. The damage range of sandwich panels shifts from localized perforation to overall deformation. Furthermore, a three-dimensional progressive damage model for composite materials is established. Impact loading simulations are conducted in ABAQUS/Explicit for three different size punches, further examining the differences in load-bearing mechanisms between the two positions. Results indicate that the load-bearing mechanism of the V-shaped structure within the core undergoes changes when subjected to impacts from punches of varying sizes, whereas the load-bearing mechanism of the arched structure remains unchanged. This paper presents a series of experimental and simulation results, which can serve as a reference for the application of double-layer foldcore sandwich structures in the field of protection.
This study presents the structural design, precision manufacturing, and compressive behavior of modularly assembled hybrid fiber composite lattice structures fabricated by continuous-fiber 3D printing. Three Kevlar/basalt hybrid fiber lattice configurations, including an unreinforced structure (N-1), a horizontally reinforced structure (Z-1), and a diagonally reinforced structure (Z-2), were designed and manufactured using an in-situ impregnation 3D-printing process combined with a modular assembly strategy. To ensure assembly quality, the effects of line width and corner geometry on manufacturing accuracy were systematically investigated. The mean dimensional deviation decreased from 0.85 mm at a line width of 1.0 mm to 0.16 mm and 0.09 mm at line widths of 1.6 mm and 2.0 mm, respectively. Compression tests revealed that the mechanical performance was jointly affected by reinforcement configuration and printing line width. At a line width of 1.0 mm, the Z-2 lattice exhibited the highest energy absorption, achieving a 129
Reliable prediction of post-demolding deformation is important in composite forming. Layer-wise finite-element models can provide such prediction accuracy, but their computational cost becomes a major concern for large composite structures. To reduce this cost, a through-thickness partitioned homogenization strategy is proposed for composite forming simulation. In this strategy, the thickness of a carbon fiber-reinforced thermoplastic cross-ply laminate is divided into several partitions, and each partition is represented by a homogenized block with equivalent thermo-mechanical properties. Four categories of through-thickness partition configurations are first defined for an asymmetric hot-pressed laminate, and their prediction accuracy and total computational time are then evaluated against a layer-wise benchmark model. The results show that global through-thickness equivalence provides the lowest computational cost but cannot deliver reliable residual-deformation prediction. By contrast, retaining surface plies on both laminate surfaces is strongly associated with physically reasonable predictions, and retaining two surface plies on each side provides a practical balance between prediction accuracy and computational cost. After the bilateral surface arrangement has been fixed, relatively balanced and relatively symmetric thickness-wise layouts are preferred when further repartition is required. Based on these results, two representative implementation routes are selected for engineering demonstration on a variable-thickness composite wing-skin component. Compared with the layer-wise benchmark model, the two routes maintain low prediction deviations, with normalized root-mean-square deviation values of 3.7
Carbon fiber reinforced polymer (CFRP) tubes serve as critical load-bearing components in aerospace and marine engineering; however, their structural reliability is profoundly influenced by the size effect. Consequently, it remains a significant challenge to directly extrapolate the damage evolution laws established from laboratory-scale specimens to full-scale engineering structures. Accordingly, radial compression tests were carried out on CFRP tubes with various dimensions in this paper. Elastic wave signals during damage evolution were captured using acoustic emission (AE) technology. To address the issues that existing damage identification models are difficult to adapt to dimensional variations, a deep learning model incorporating a self-attention mechanism was constructed to realize the intelligent identification of damage modes for CFRP tubes with different dimensions. The results demonstrate a pronounced size effect in the mechanical performance of CFRP tubes: upon normalization, the peak load and displacement of the large-scale specimens decreased by 3.8
Fiber–metal laminates (FMLs) combine the advantages of metallic layers and fiber-reinforced composites; however, interlaminar delamination remains a critical failure mechanism limiting their structural reliability. In this study, the Mode-I interlaminar fracture behavior of glass/epoxy/aluminum laminates (GLARE) was experimentally investigated as a function of interfacial fiber architecture, including AL//0, AL//90, AL//plain-woven, and AL//glass-mat configurations. Double Cantilever Beam (DCB) tests were conducted in accordance with ASTM D5528 to evaluate the strain energy release rate and crack propagation characteristics. The results reveal that interfacial architecture plays a dominant role in governing fracture resistance. The AL//90 configuration exhibited the highest propagation toughness (≈ 1645–1720 J/m²), nearly twice that of the AL//0 interface (≈ 611–700 J/m²), despite the presence of significant fiber bridging in the latter. Woven interfaces showed reduced and and glass-mat highly heterogeneous fracture responses due to tow undulation and random fiber distribution, respectively. Fractographic analysis identified distinct crack propagation mechanisms, including fiber pull-out, bridging, and interfacial debonding, which directly correlate with the measured energy-release behavior. A cohesive zone model (CZM) was implemented to simulate delamination initiation and propagation, showing good agreement with the experimental load–displacement responses while capturing the overall fracture trends across different interface configurations. The findings demonstrate that interfacial fiber architecture governs delamination resistance more strongly than bridging effects alone, providing critical insight for the design and optimization of FML structures.
