Basalt is a mineral-based, high-performance, sustainable reinforcement with a novel combination of high performance and competitive cost, offering superior chemical durability and thermal stability compared to E-glass, while being significantly more cost-effective than carbon fiber. This review summarises recent advances in “lava-to-lightweight” connecting production of basalt fibers (melt spinning, drawing, and sizing) to composite production pathways, performance and applications. The literature is classified into common design levers: (i) effective length of load transfer (fiber length continuity), (ii) reinforcement architecture and alignment, (iii) engineering of interphase (size, chemical coupling, hierarchical coatings), and (iv) wear, impact and aggressive environments damage and durability pathways. Basalt fiber–reinforced composites exhibit mechanical performance between glass and carbon fiber composites, with tensile strengths up to 417 MPa, higher than natural fiber composites and comparable to or slightly higher than glass fiber composites but lower than carbon fiber composites. This positions basalt fibers as a balanced reinforcement with superior durability having competitive strength-to-cost performance. The strength and stiffness of these composites mainly depend on how the fibers are arranged and fiber-matrix adhesion. Their long-term durability is affected by moisture and chemical ingress into the composite, which can cause the matrix to hydrolyse and weaken the fiber-matrix bond, especially under repeated wet-and-dry conditions. Their application readiness is evaluated across key areas: mobility, aerospace, marine, construction/infrastructure, and electrical/electronic. However, challenges identified include the lack of standardized testing, limited data on long-term performance in real environments, and unclear recycling or disposal options at the end of their service life. Lastly, sustainability factors are summarised for production energy, emissions, and recyclability opportunities, and a roadmap is proposed for scale-up through process monitoring, data-driven optimisation, and qualification standards.
Carbon fiber-reinforced polymers (CFRPs) have become indispensable in high-performance structural applications because of their high specific strength, stiffness, corrosion resistance and design flexibility; however, their mechanical behavior is governed by heterogeneous microstructures and manufacturing-induced defects that make accurate structure–property prediction difficult using conventional approaches. Traditional evaluation methods based on destructive experiments and multiscale finite element analysis (FEA) provide high fidelity but remain limited by time-intensive workflows, high computational cost, and simplifying assumptions regarding microstructural uniformity. These limitations have accelerated the adoption of machine learning, particularly deep learning, as an efficient surrogate framework for forward prediction of mechanical response directly from microstructural representations. Recent studies have shown that deep learning models can predict effective properties, full-field stress and strain responses, and damage evolution directly from image-based, feature-based, or hybrid representations of CFRP microstructures. However, existing reviews largely address AI in composites from a broad lifecycle perspective and do not systematically synthesize deep learning methods developed specifically for micromechanical structure–property prediction in CFRPs. This review fills that gap by classifying the literature according to microstructural input representation, physics integration level, and mechanical behavior regime (from linear elasticity to damage and failure), while also examining data generation strategies, computational efficiency, validation practice, and generalization capability to clarify current progress and identify priorities for robust, physically consistent, and industrially relevant predictive modeling.
Continuous carbon fiber reinforced silicon ceramic matrix composites (C/SiC) is a well-known high-performance material for structural parts of the hot end serving in extreme environments. To achieve the 3D/4D printing of C/SiC structures, the effects of the densification process, fiber volume fraction, fiber prestress, and high-temperature heat treatment on the mechanical property and thermal expansion property of unidirectional C/SiC were studied. The results show that the densification of C/SiC can be achieved quickly by combining chemical vapor infiltration (CVI) with polymer infiltration and on-line pyrolysis(PIOP) (CVI+PIOP); the higher the fiber volume fraction is, the lower the bending strength is and the smaller coefficient of thermal expansion (CTE) is; the best fiber prestress is 45MPa. By confirming the additive manufacturing controlling parameters on the mechanical property and thermal expansion property of unidirectional C/SiC, this paper provides guidance for the design and 3D/4D (three-dimensional/four-dimensional) printing of C/SiC Metamaterial structures.
Flax fiber–reinforced polypropylene (Flax/PP) composites offer a sustainable alternative for lightweight automotive structures, but their mechanical durability and crashworthiness under moisture exposure remain insufficiently understood. This study integrates moisture diffusion, mechanical characterization, single-fiber testing, nanoindentation, X-ray computed tomography, and progressive crushing to examine moisture-induced degradation across multiple length scales. Water uptake exhibited early-time Fickian behavior, with similar equilibrium moisture contents across laminate thicknesses but thickness-dependent times to saturation. Mechanical testing revealed strongly loading-mode–dependent degradation. Flexural and shear stiffness showed the greatest reductions, whereas tensile strength was comparatively less sensitive to moisture exposure. Combined-loading compression exhibited an apparent increase in compressive modulus after water conditioning while compressive strength decreased substantially. Progressive crushing tests showed reductions of up to 45% in steady-state crush stress, specific energy absorption, and crush force efficiency after moisture conditioning. In contrast, single-fiber tensile testing combined with Weibull analysis indicated that the intrinsic tensile properties of the flax fibers were largely retained following conditioning. Together, the multiscale observations suggest that the measured degradation is consistent with moisture-induced matrix plasticization and changes at the fiber–matrix interface, which can alter the mechanisms governing stable progressive crushing. These findings establish an experimentally supported mechanistic framework for interpreting the durability and crashworthiness response of moisture-conditioned natural-fiber thermoplastic composites.
A single computational framework is proposed in which several plate kinematics are solved by training neural networks to minimize the discretized total potential energy of the laminate, so that residual-form governing equations are never assembled. The energetic contributions are integrated analytically using the symbolic package SymPy, which also enables the automatic generation of lambda functions from the symbolic expressions. The computational implementation was carried out in PyTorch, considering two equivalent single-layer plate models. The adopted models comprise the Reissner–Mindlin First Order Shear Deformation Theory (FSDT) and a Carrera Unified Formulation representation. Predicted displacement and stress fields are compared against finite element reference solutions, and the metrics used to evaluate this agreement are the RMSE and relative error.
This study presents an advanced method for real-time inspection and quantitative evaluation of progressive damage in very large thin-walled fiber/polymer composite structures, such as wind turbine blades and aircraft wings, under cyclic loading typically conducted in fatigue tests for prototype certification. The method, based on thermography, captures thermographic abnormalities to locate potential regions of imminent damage. Subsequently, quantitative thermal analysis of the regions of interest is conducted, providing real-time structural health monitoring capabilities for early warning of damage without interrupting certification tests, as is currently done in industry practice. The method is implemented in a solution package named as AQUADA170m+ which consists of both hardware and software, and it is demonstrated at a large-scale commercial test center for testing wind turbine blades that could be over 170 m in the coming years. The method presented in this study bridges an important gap between the current state of the art in thermographic inspection and the industry’s urgent need for a more efficient technique for non-stop, non-contact, and real-time damage inspection and quantification of very large composite structures.
Nowadays, sandwich panels are widely used in various industries such as shipbuilding, and automotive due to their good bending, compressive, and impact strength, light weight, cheap, and easy manufacturing method. Separating the core from the shell, as two important components, is a significant challenge when using these components. Accordingly, in this study, the effect of placing self-healing microcapsules on the reconnection of the core-shell at the site of damage, as well as on the recovery of the mechanical properties of sandwich structures, was investigated. Sandwich panels were made of a polyvinyl chloride foam core and an epoxy-glass fibers composite shell. Microcapsules were used to store epoxy resin, and 3-ethylene tetra amine (TETA) hardener and methyl imidazole catalyst were stored in specific amounts inside the sandwich panel layers. The samples were subjected to three-point bending and tensile tests at different microcapsule (5, 10, and 15 wt.%). Also, field emission scanning electron microscopy (FESEM) and optical microscopy (OM) were taken to show that the microcapsules were successfully fabricated, dispersed and attached to glass fibers to reconnect core-shell interface. The mechanical test results showed that the best bending and tensile strength was achieved for samples containing 15 wt.% microcapsules with catalyst, with both values reaching 28.1 MPa. Moreover, they had the repair efficiency of 83.69% in bending and 77.69% in tensile test. The recovery of mechanical properties after damage and the passage of repair time indicate that repair has occurred at the microcapsule core-shell interface.
Composite overwrapped pressure vessels (COPVs) are central to high-pressure hydrogen storage, where low mass and structural integrity under burst conditions are simultaneously critical. Optimising their stacking sequences is difficult because the governing failure mechanism changes through the wall thickness, and because established failure criteria diverge appreciably under the multiaxial stress states produced by internal pressure. Designing to the most critical predicted mode is standard engineering practice; what is not established is how to embed that practice inside an automated optimisation loop, and what it delivers when it is. This study integrates the Tsai–Wu interactive quadratic, Hashin mode-separated fibre/matrix, and Puck inter-fibre failure (IFF) criteria into a triadic envelope the point-wise maximum failure index over a discretised radial profile and places that envelope directly in the fitness function of a genetic algorithm (GA), so that the governing criterion is resolved radially and per layer rather than assumed in advance. Ply stresses are obtained from a Lekhnitskii-type thick-walled multilayered anisotropic cylinder solution under generalized plane strain with closed-end axial equilibrium. Applied to a benchmark linerless (Type V) cylindrical COPV of 174 mm internal radius and 175 MPa burst pressure, the triadic formulation yields a 36-layer configuration of 54.24 mm wall thickness, with a maximum combined failure index of 1.12 and a layer exceedance rate of 5.6%. Evaluated under identical design constraints, this halves the cross-criterion exceedance rate relative to the Hashin-only (1.18, 11.1%) and Puck-only (1.07, 11.1%) designs, at a wall thickness 5.6% greater than the least conservative Tsai–Wu-only design (0.97, 0%). The balance of ply orientations across the low-, mid- and high-angle ranges is an explicit constraint of the fitness function rather than an emergent property of the envelope; holding it fixed across all four runs isolates the effect of the failure measure itself. The analytical solver is verified against the closed-form Lamé solution in the isotropic limit and against the boundary, interface and axial-equilibrium conditions of the multilayer problem.
Quick and selective dismantling of resin adhesives is significant to establish the resource circulation for composite materials consisting of various materials. In this study, we used an electrical pulsed discharge method to dismantle a model bonding structure, in which two metals are adhered by epoxy resin adhesive. A limitation of this method is the lack of precise control over the discharge position for efficient delamination. To overcome this problem, we aimed to design the discharge position in the epoxy adhesive by the addition of conductive Ag nanoparticles. We found that Ag nanoparticles formed aggregates. The size of the aggregates was about 200 nm, and it did not depend on the Ag concentration, whereas the distance between aggregates decreased as the Ag concentration increased. These aggregates can form a current path for the electrical pulsed discharge, resulting in successful debonding by the pulsed discharge method. The debonding behavior by the electrical pulse discharge and the structure of the aggregates of Ag particles in epoxy resin adhesive was analyzed. It was found that the pulsed discharge behavior in the epoxy adhesive with Ag nanoparticle can be characterized by the average distance between the surface of the closest two aggregates normalized by the size of the aggregates: if it is less than 5, the possibility of the internal discharge is close to 1. This experimental result agrees with the electric filed simulations.
Ultrasonic welding offers considerable potential to replace conventional adhesive or thermal bonding techniques. This study investigates a hybrid process combining laser beam powder bed fusion and continuous fiber reinforcement. After printing, the laser beam powder bed fusion substrate is reinforced with a composite tape on the outer surface using continuous ultrasonic welding. The quality of the joint weld is analysed based on the lap shear strength between the joining partners. The results show a maximum lap shear strength of approximately 21.4 MPa. Compared with other continuous fiber 3D printing / additive manufacturing technologies, ultrasonic welding can achieve lap shear strength values that are 45 to 104 % higher. The results indicate that the optimal parameter window for this process-material combination is achieved at a lower welding speed, a sonotrode amplitude of 27 μm and a welding pressure of approximately 0.5 MPa.
This study presents a computational framework for evaluating the mechanical behaviour of flake-based recycled composites. Three-dimensional representative volume elements (RVEs) are constructed to estimate effective elastic properties and capture local stress distributions. The influence of meso‑structural features, such as out-of-plane flake orientation, flake length, and resin-rich regions, on RVE size and representativeness is systematically investigated to ensure accurate and reliable predictions. Furthermore, the effect of flake length on both local and global mechanical responses is examined in detail. The results demonstrate that the composite’s effective properties are governed by flake length: the in-plane elastic moduli increase with longer flakes, whereas the out-of-plane properties remain largely unchanged. Locally, longer flakes develop more uniform longitudinal and out-of-plane stresses, while the in-plane and resin stresses tend to increase. The proposed framework provides a basis for the design and optimisation of recycled composites, supporting the development of high-value circular composite systems.
The structural integrity of composite-metal bolted joints in fan casings is critical for preventing catastrophic failure under high-velocity blade-off conditions. This study investigates the impact response, energy absorption characteristics, and progressive damage evolution of these connections using high-speed air cannon experiments coupled with a three-dimensional continuum damage model (CDM). Implemented via a VUMAT subroutine, the numerical approach effectively captures progressive intralaminar and interlaminar failure modes, with accuracy validated against experimental residual velocity and damage morphology. Analyses reveal that the mounting edge radius acts as a primary stress concentration locus susceptible to severe delamination and fiber rupture. Structural impact resistance is maximized at the connection center due to superior load sharing, while being highly sensitive to hole-to-edge distance and laminate thickness. Using a surrogate-model-based multi-objective optimization framework combining RBF neural networks and genetic algorithms, the optimized configuration achieved a 45.3% reduction in residual kinetic energy and a 2.3% reduction in structural mass, demonstrating improved impact resistance while maintaining lightweight characteristics.
This study focuses on carbon fiber/bismaleimide (CF/BMI) composites, in which intralaminar reinforcement and interfacial structure optimization are achieved by introducing rigid nanoparticles with distinct geometric structure characteristics (spherical nano-SiO2, tubular carbon nanotubes (CNTs), and sheet-like graphene (Gr)) into the BMI matrix. The results revealed a notable correlation between the geometric structure characteristics of nanoparticles and the mechanical performance of modified CF/BMI composites. Among the investigated nanofillers, CNTs exhibited the most pronounced reinforcing effect owing to their high aspect ratio and tubular structure, which facilitated the formation of a more efficient load-transfer network and stronger interfacial mechanical interlocking. As a result, the flexural strength, flexural modulus, and interlaminar shear strength (ILSS) increased by 21.08%, 9.34%, and 16.89%, respectively. Based on these findings, CNTs were selected as the preferred nanofiller to further investigate the effect of CNT content (0.1, 0.3, and 0.5 wt%) on the mechanical properties of CF/BMI composites. The results showed that the mechanical properties first increased and then decreased with increasing CNT content. Furthermore, the study pointed out that good initial dispersion of CNTs in the resin was only a prerequisite; the fiber filtration effect and resin reflow/redistribution during prepreg fabrication and laminate molding ultimately determined their final dispersion state. This work can provide a theoretical basis and technical reference for interfacial design and formulation optimization of high-strength CF/BMI composites.
Externally bonded fibre-reinforced polymer (FRP) systems are widely used for flexural strengthening of reinforced concrete (RC) members because of their high strength-to-weight ratio, corrosion resistance, and ease of installation. This study investigates the flexural behaviour of RC beams strengthened with carbon fibre-reinforced polymer (CFRP), polyethylene terephthalate fibre-reinforced polymer (PET-FRP) laminates and their hybrid combinations. Fifteen full-scale RC beams, each measuring 2000 mm in length, 300 mm in depth, and 150 mm in width, were tested under flexure in a four-point bending configuration to assess the effects of different FRP types, number of layers, hybrid stacking sequences, and U-wrap anchorage systems. Detailed assessments of load–deflection behaviour, load–strain response of reinforcing steel, load–strain behaviour of FRP laminates, beam ductility, and failure modes were carried out. The results showed that a single CFRP layer increased the yield and ultimate loads by 13% and 39%, respectively, relative to the control beam, whereas two CFRP layers increased them by 48% and 70%. For the two-layer hybrid systems, CFRP–PET-FRP and PET-FRP–CFRP increased the ultimate load by 53% and 49%, respectively, compared with the control beam. The introduction of U-wrap anchorage generally delayed premature debonding and enhanced the post-yield deformation capacity, with the PCP-U specimen exhibiting 67% higher ultimate ductility and 200% higher failure ductility than the corresponding unanchored PCP specimen. Comparison with ACI 440.2R-17 and CEB-FIB design guidelines indicated that ACI predictions showed closer agreement with the experimental results for the specimens investigated. The findings highlight the potential of hybrid combination CFRP and PET-FRP systems in providing a balanced improvement in strength and ductility for flexural deficient RC beams, although the effectiveness depends strongly on the laminate stacking sequence and anchorage configuration.
The application of composite materials has been recognised as an excellent alternative for hydrocarbon pipelines, offering solutions to the significant issues of corrosion commonly associated with traditional carbon steel pipelines. The utilisation of composite materials has been a viable option since World War II; however, their adoption was hindered by the exceptionally high costs associated with their production over the last few decades. Nowadays, some of the critical concerns relating to traditional carbon steel pipelines, such as the high maintenance costs, have led to the realisation that composite materials are currently a better alternative for oil and gas applications. Nevertheless, throughout their operational lifespan, composite pipelines are susceptible to degradation and may encounter failures, including cracking and delamination, as a result of various internal or external factors. Fortunately, numerous studies have comprehensively addressed these challenges by conducting practical experiments to clarify their failure mechanisms, contributing factors, and limitations. However, studies to address/understand the necessary inspection and testing techniques, manufacturing processes, and maintenance procedures of composites in the oil and gas industry are yet to be conducted. This review uniquely integrates material selection, manufacturing processes, degradation mechanisms, and inspection and maintenance strategies into a unified framework for assessing the performance and long-term reliability of composite hydrocarbon pipelines. Therefore, this study aims to provide a comprehensive overview of composite hydrocarbon pipelines, with a focus on their feasibility as a sustainable substitute for conventional metallic pipelines. Thus, this research offers an in-depth understanding of the choice of optimal materials, state-of-the-art manufacturing methods, and recent advancements in testing, inspection, maintenance practices, and sustainability. Moreover, the study offers insights into several factors that are currently influencing and impacting the functionality and performance of non-metallic pipelines.
Flax fibers and aluminum alloys each have their own advantages and disadvantages. Flax fiber aluminum metal laminates (FMLs) capitalize on their strengths while overcoming their weaknesses and have been widely applied across various fields. This work evaluated the geometrical shape of the holes by measuring diameter (D), roundness error (Re), and the difference in D at the two ends of the hole (ΔD), as well as studied the surface integrity of the holes by measuring mean roughness (Ra) and examining machining damage induced by abrasive waterjet (AWJ) processing. The X-ray CT (μ-CT) and the scanning electron microscope (SEM) confirmed that minor interply delamination occurred in only a few holes. The AWJ drilling (AWJD) damage in this work is much less severe than that of aluminum alloys and flax fibers, primarily due to the predrilled holes. The mechanism of interply delamination was discussed. No abrasives contaminated any of these holes. This work introduced a new parameter, named “the index of impact force”, to quantitatively describe the relationship between the AWJD parameters and interply delamination, and successfully predicted the occurrence of interply delamination. In conclusion, predrilling, followed by AWJD, is a suitable approach for creating high-quality holes in woven flax FMLs.
Delamination represents one of the most prevalent failure modes in laminated composite structures. To better understand this phenomenon, its driving mechanisms are investigated from a thermomechanical standpoint under quasi-static loading using a Double Cantilever Beam (DCB) configuration. Full-field measurements, namely digital image correlation (DIC) and infrared thermography (IRT), are employed on a novel DCB testing rig to capture the energy dissipated as heat during crack propagation. Fracture toughness is characterized using an analytical expression derived from beam theory, adapted to this specific setup. Finally, a fine-tuned meso-scale finite element model is used to analyze the thermomechanical behavior of the specimens. Specifically, the model shows that an increase in loading rate enhances the thermal signature, which facilitates IR measurements.
Closed-type winding (CW) ties have emerged to overcome limitations of conventional Glass Fiber Reinforced Polymer (GFRP) ties, particularly overlap slippage and low confinement efficiency. Although their effectiveness under axial loading has been widely reported, their performance under lateral loading across a range of conditions remains insufficiently understood. This study evaluates the lateral behaviour of GFRP-reinforced concrete columns with CW ties, compares their effectiveness with conventional ties, and proposes design recommendations to satisfy both strength and deformation requirements. A numerical model was developed and validated against previous experimental results. Subsequently, a parametric study was conducted considering shear span-to-depth ratio, axial load, concrete strength, tie size, tie spacing, and tie configuration. The results demonstrate that CW ties significantly enhance lateral performance compared with conventional ties. The reduction in deformation capacity caused by low shear span-to-depth ratios and high axial loads was effectively minimised using CW ties. In addition, CW-GFRP ties improved confinement efficiency and reduced the adverse effect of high-strength concrete on deformability. Columns confined with CW ties also showed higher capacity improvement with increasing concrete strength, achieving performance comparable to spiral-confined columns. Tie size and spacing had limited influence on the lateral performance under low column axial loads but became more critical at higher axial loads, improving post-peak stability and enabling a second peak load. The most favourable performance was achieved with a concrete compressive strength of 50 MPa, a tie volumetric ratio exceeding 1.85%, tie spacing equal to 0.25 of the column width, and a hybrid confinement system combining outer square and inner circular ties.
Tailored Fiber Placement (TFP) is an additive manufacturing process for composite materials. It is based upon the embroidery technique, where continuous fiber rovings are positioned in a textile base material, fixed by a stitching yarn, and are later impregnated in a matrix. Its main advantage consists of the high design freedom, allowing the production of variable-axial reinforcements, depositing fibers only where desired and with optimized orientation. However, when dealing with small dimensions, deviations can be clearly observed between the target path (designed path) and the actual path, effectively stitched by the TFP machine. Among the sources for these deviations, one can mention fiber’s waviness, buckling, materials involved, influence of input parameters, i.e., the tension applied at the roving, the distance between stitching points, speed, and other systematic deviations inherent to any manufacturing process. The present work focused on measuring these deviations and analyzing the influence of the stitching parameters on them. It was observed that the distance between stitching points plays a major role in this regard. After collecting the stitching data with varying inputs, a machine learning algorithm was trained to predict the deviations and to propose a second target path, whose objective is to minimize the deviations between the first target path and the actual path. The machine learning algorithm was able to minimize the average deviation over the target path by up to 55%.
This study examines the behavior of a glass-filled, intumescent, flame-retardant polypropylene (FR-PP). It extends previous investigations by incorporating the contributions of both solid and gaseous phases into the through-thickness thermal conductivity of intumescent composite systems across multiple spatial scales and under varying orientations of external fire exposure. Thermal computational models were developed and validated against experimental measurements.Two different approaches are used for the thermal loads. Firstly, the pyrolysis behavior of the material, along with relevant test geometries and boundary conditions, was modeled using PyroSim, which utilizes the Fire Dynamics Simulator solver. The model captures the material’s multi-step degradation kinetics, including reactions in the condensed and gas phases and associated phase transitions. Material properties were experimentally characterized, and reaction parameters were extracted through multiple analytical techniques. Secondly, an inverse heat transfer approach was applied to a surrogate stainless-steel plate to estimate the transient spatial heat flux distribution, enabling the quantification of thermal loads across a broad spectrum of complex fire exposure scenarios without necessitating explicit consideration of combustion or pyrolysis, nor reliance on direct temperature measurements at the exposed, actively burning surface of specimens. The resulting heat fluxes were mapped onto an Abaqus finite element analysis model as transient, spatially varying thermal loads.This study establishes lower and upper bounds for temperature prediction by applying series and parallel multiphase approaches, respectively, under each fire scenario. It also presents the interpretation of thermal conductivity, not merely as a temperature-dependent property, but also as a function of the rate of thermal exposure.
