Journal of Reinforced Plastics and Composites

Homogenized laminates offer great advantages for design optimization, tapering, and simpler manufacturing. This can be achieved by stacking identical building blocks, so the laminate normalized in-plane stiffness components converge to the flexural stiffnesses. In this research, it was shown that the rate of convergence of quadriaxial laminates varies with layup. A family of three quadriaxial carbon fiber reinforced plastic CFRP laminates showing the fastest convergence was studied: one quasi-isotropic [+45/−45/0/90] and two hard [+45/−45/0₂/90] and [+45/−45/0₃/90]. The study showed that the ratios between the average strengths of different quadriaxial laminates will be the same for a given material. In addition, for a given quadriaxial laminate, the relative strengths between CFRP materials are the same. In summary, this investigation opens new opportunities for design and manufacturing that can be explored with homogenized quadriaxial laminates, providing a framework for engineers to select layups based on predictable convergence rates and strength relationships.

Fused filament fabrication (FFF) of semi-crystalline polymers, such as polyamide 11 (PA11), is challenging due to significant shrinkage that occurs during cooling. This issue can be mitigated by blending the polymer with chemically compatible additives, which alter its rheological, thermal, and mechanical properties, thereby improving processability. In this study, we demonstrate the successful FFF printability of PA11 filaments modified with an ethylene–acrylic acid copolymer grafted with maleic anhydride (EAA-g-MAH) as an impact modifier. Carbon nanotubes (CNTs) were incorporated to compensate for the loss in terms of stiffness caused by the addition of EAA-g-MAH compound. Bulk compositions were prepared via melt compounding and compression molding and characterized, revealing that the addition of 20 wt% EAA-g-MAH increased the specific impact energy of PA11 by 282%. Two optimized impact-modified PA11 formulations—with and without CNTs—were subsequently extruded into filaments and, for the first time, successfully 3D printed through FFF. Mechanical testing demonstrated substantial improvements in ductility for the 3D-printed specimens, with increases of up to 56% for unfilled PA11 and 105% for CNT-reinforced PA11, relative to their bulk counterparts. This work opens new possibilities for directly printing tough polymers onto reinforcing fibers to create self-healing composites. Additionally, strong interfacial adhesion was achieved between glass fibers and the printed CNT-reinforced PA11, suggesting a potential increase in interlaminar toughness in fiber reinforced polymers (FRPs). These multifunctional materials processable via FFF represent a promising step toward the development of smart, self-healing structural composites.

This work investigated the flexural performance of glulam wood–polyvinyl chloride composite hollow members (GWPVC), fabricated by assembling individual wood–polyvinyl chloride composite (WPVC) elements with epoxy adhesive and strengthened in singly and doubly reinforced configurations. Shear bonding strength tests were conducted to confirm that the capacity satisfied standard requirements. Several strengthening materials, including carbon fiber-reinforced polymer (CFRP), low-cost glass fiber-reinforced polymer (LC-GFRP), and steel, were evaluated using the VIKOR method within a multi-criteria decision-making (MCDM) framework based on mechanical performance. Steel was identified as the most suitable strengthening material. The study highlights steel strengthening as an approach to improve the flexural performance and serviceability of GWPVC members, with predictions from analytical method with iterative technique (AMIT) that considers shear deformation effects and finite element method (FEM) simulations, validated against experimental results. Four-point bending tests showed that the ultimate load and initial bending stiffness increased by up to 220.63% and 109.22%, respectively, compared with unstrengthened specimens. Parametric results from AMIT demonstrate that flange reinforcement is more effective than web reinforcement, particularly when placed farther from the neutral axis. Strengthening also extended the serviceable span length of GWPVC members from 3.38 m to 5.27 m, confirming feasibility for residential prefabricated floor panel applications.

Graphical Abstract

This study is focused on failure of single-face honeycomb core sandwich beams loaded in four-point flexure. The beams are configured for pure moment loading of a single-face sandwich (SFS) where the lower region of the core is under compression. Failure of the beam is assumed to occur when the maximum compressive strain in the core reaches its ultimate value in uniaxial compression. Analysis of the stiffness and failure load of the beam utilizes laminate beam theory. Constraint on the dominant bending deformation of core cell walls develop in honeycomb core sandwich structures because the cell walls are adhesively bonded to rigid face sheets. This constraint elevates the effective extensional modulus of the core. This effect is incorporated in the analysis by replacing part of the core with a gradient layer. Single-face sandwich beam specimens consisting of carbon/epoxy face sheets and Nomex honeycomb core were tested in flexure. Experiments and analysis demonstrate that the one-sided constraint on the core significantly increase the bending stiffness and bending strength of the single face sandwich beams. For a typical SFS specimen, it is shown that the constraint elevates the stiffness and strength by 13 and 16%, respectively. The gradient core model predictions of the failure load of the single-face specimens are in good agreement with experiments.

This study presents a baseline-free, self-supervised framework for defect detection in carbon fiber–reinforced polymer (CFRP) laminates using laser ultrasonic guided wave (LUGW) wavefield data. The experimental investigation involves two quasi-isotropic eight-ply laminates with a [0/45/90/−45]_S stacking sequence, each containing an artificial defect made by a centrally embedded square PTFE insert (10×10 mm² and 5×5 mm²) at the mid-plane to simulate local delamination. Data preprocessing includes narrowband temporal filtering centered on the dominant carrier frequency and frame-wise spatial detrending, followed by tri-planar decomposition of the spatiotemporal wavefield volume. Each orthogonal plane is processed independently using attention-assisted blind-spot U-Nets trained through masked-pixel restoration, producing per-pixel posterior means and log-variances. The three probabilistic estimates are fused using a product-of-experts (PoE) model, yielding a unified prediction with calibrated uncertainty. A standardized residual between the observed data and the fused prediction is used to drive adaptive thresholding and morphological post-processing, resulting in coherent delamination masks. The uncertainty-aware fusion strategy effectively down-weights low-information regions and mitigates boundary artifacts. A dual decision criterion based on the area fraction and the mean anomaly score enables robust detection. The proposed pipeline achieves accurate and interpretable delamination localization without reliance on prior knowledge of structural properties, defect presence, baseline measurements, or labeled training data.

The use of advanced thermoplastics in aircraft applications is steadily increasing due to their excellent mechanical strength and thermal stability. This study investigates Carbon Fibre Reinforced Polyphenylene Sulfide (CF/PPS) composites utilising a 5-Harness Satin (HS) fabric. Quasi-isotropic laminates with two different thicknesses underwent a thermoforming process at varying tool temperatures. The objective is to evaluate the effect of the degree of crystallinity (DOC) on the mechanical properties, specifically Impact Strength and Interlaminar Shear Strength (ILSS), as well as on thermal properties through Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) analysis. The results show that the DOC of CF/PPS in both 6- and 8-ply samples led to an improvement of over 50% in impact strength. Furthermore, ILSS increased by 15.3% and 10.38% at tool temperatures of 170°C and 160°C for the 6 plies and 8 plies laminates, respectively. TGA analysis after stamping indicated improved thermal stability with higher residual content, suggesting enhanced char formation. Lastly, for DSC results, DOC demonstrated 22.8% crystallinity after the thermoforming process, further supporting the correlation between DOC and mechanical performance.

This study investigates the repair potential of carbon/polyamide 6 specimens after extensive hydrolytic degradation, using double cantilever beam (DCB) characterization. To evaluate repair effectiveness, DCB test results from repaired specimens were compared with those from aged but unrepaired specimens. The results indicate a reduction in mode I fracture toughness G_IC for most repaired specimens compared to their unrepaired counterparts (from 3.44 kJ/m² down to 0.94 kJ/m² in the non-repaired state compared to 2.44 kJ/m² down to 0.84 kJ/m² in the repaired condition). However, as ageing duration increased, the difference in G_IC values between repaired and unrepaired specimens progressively decreased, eventually converging for the longest ageing duration studied (from −29% in the unaged state down to −10% for the ultimate degradation duration). To understand this behaviour, complementary analyses, including molar mass and crystallinity ratio measurements, X-ray tomography, and SEM observations, were conducted. These investigations suggest that fibre misalignment and a weakened fibre/matrix interface after repair contributed to the observed reduction in G_IC for a given ageing duration. While prior studies have addressed the repair of thermoplastic composites, the effect of hydrolysis on their repairability remains largely unexplored. This work highlights the repair potential of thermoplastic composites even after significant irreversible degradation.

This study investigates the delamination failure mechanisms of T700/8911 carbon fiber reinforced polymer (CFRP) composites in seawater environments through combined experimental and numerical approaches. Three-point bending tests were conducted on specimens with [0°₁₆//0°₁₆], [0°/90°]_4s//[0°/90°]_4s and [15°/-15°]_4s//[15°/-15°]_4s layup patterns under both ambient (25°C) and accelerated hygrothermal conditions (70°C temperature and 95% relative humidity). Experimental results revealed that moisture absorption caused a 23–37% reduction in interfacial bond strength. This reduction significantly altered failure modes from classical delamination to predominant interfacial debonding. The finite element model developed in ABAQUS incorporated humidity-dependent cohesive zone parameters and modified traction-separation laws, achieving excellent correlation with experimental data. Key findings demonstrate that hygrothermal exposure increases interlaminar fracture toughness while reducing in-plane modulus, leading to higher critical loads (28–35% increase) but lower stiffness in the linear elastic stage. The cohesive zone modeling approach successfully captured the three-phase delamination process: initial elastic deformation, critical crack initiation, and stable propagation. Analysis of mode mix ratios showed cohesive elements transition from shear-dominated to tensile-dominated damage as delamination progresses. The study establishes quantitative thresholds for interfacial stiffness reduction (15–20%) and provides a validated modeling framework for predicting performance degradation of marine composites, offering valuable insights for designing durable offshore structures in seawater environments.

Advances in stimuli-responsive materials have led to increasing popularity due to their ability to adapt intelligently and be capable of “remembering” their original shape after adopting temporary deformed shapes in various applications. At the same time, the environmental and sustainability challenges of end-of-life (EOL) disposal for these materials are particularly concerning. This review synthesizes current knowledge on how sustainable chemistry and functional material design can be bridged by integrating waste, as an effort to reach a closed-loop circular economy, into high-performance shape memory benzoxazine-based thermosets. Both agricultural and industrial waste streams, including lignin, vanillin, eugenol, diphenolic acid, and cardanol, were systematically discussed, exploiting each unique functional characteristic, such as phenol, aldehyde, allylic, carboxyl, and alkyl groups, to be utilized as valuable target sites for chemical modifications from phenolation, esterification, amination, imination, hydrothiolation and thiol functionalization, inverse vulcanization, and direct condensation to enable the shape memory effect with a controllable end-of-life (EOL) scenario. Thermoset materials initially designed with degradable linkages can be reshaped, healed, or degraded under specific triggers and conditions, retaining their properties for several reprocessing cycles until they reach their performance limits. In contrast, networks lacking dynamic functionality usually display long-term stability during service, but they require more advanced technologies for EOL management. In such cases, methods such as catalytic oxidation can be used to recover valuable fiber and resin fragments, which typically necessitates more complex processing procedures. The choice between these recycling methods should be based on the intended use, the service environment, and the desired EOL option. Implementing the waste-to-value concept with these advanced strategies undoubtedly offers environmental benefits, but it also entails “hidden costs,” such as increased processing complexity, catalyst requirements, or purification procedures, which must be weighed carefully to avoid outweighing the advantages. We conclude by outlining key areas of future advancement, with a particular emphasis on the need for thorough life-cycle and techno-economic evaluation of these waste-derived benzoxazine-based systems to transition them from laboratory proof-of-concept to operational, predictive, and industrial-scale circular systems.

Graphical Abstract

This paper aims to develop a high-performance, cost-effective ceramic coating on AISI 1020 steel substrate. For this purpose, three kinds of conventional ceramic powders are taken in the composition Al₂O₃+3 wt%TiO₂, WC+12 wt%Co and ZrO₂+8 wt%Y₂O₃. The composites are coated on the steel surface using thermal spraying technology such as plasma flame for Al₂O₃+3 wt%TiO₂ and ZrO₂+8 wt%Y₂O₃ and high-velocity oxy-fuel for WC+12 wt%Co deposition. Recently, carbon nanotube–reinforced ceramic materials have gained more attention because of their excellent surface morphology properties. Adding nanocomposite to ceramic powders can considerably increase the microstructural characteristics and microhardness of thermal sprayed coatings. However, it is still challenging to obtain effective nanocomposite-doped conventional coating due to the elevated temperature of heat equipment. Thus, the conventional ceramic powders Al₂O₃+3 wt%TiO₂, WC+12 wt%Co and ZrO₂+8 wt%Y₂O₃ are combined with carbon nanotubes at a weight ratio of 1%, 3% and 5% for preparing reliable nanocomposite ceramic coating. The properties of nanocomposite mixed coatings are studied, and their performance is compared with conventional coatings. The coatings’ morphology, structure and phase composition are investigated through scanning electron microscopy and X-ray diffraction. In addition, Vickers microhardness and surface roughness are also determined.

The prime importance of this work is that to compare the influence of hygrothermal analysis on the physical properties of different variant of interpenetrating polymer network (IPN) blend reinforced with E-Glass/Carbon and combination of both (hybrid) fibers. In this study, combinations of epoxy (EP)/polyurethane (PU), vinyl ester (VER)/polyurethane (PU), and epoxy (EP)/vinyl ester (VER) have been taken as the matrix material (IPN) to reinforce the glass, carbon, and combination of both fibers. Moreover, prepared specimens are subjected with boiling water immersion test by maintaining the temperature of 45°C, 55°C, and 65°C in order to thoroughly understand the influence of moisture absorption and temperature in their physical attribution as per ASTM standards. Besides, to better understand the thermal stability and compatibility, thermal-gravimetric (TGA) analysis and burn-off test were conducted as well. During this study, it was found that, combination of VER/PU possesses the high moisture absorption resistance amongst all variants (0.725% for 45°C, 0.854% for 55°C, 1.234 for 65°C). Similarly, epoxy/vinyl ester reinforced glass fiber IPN laminate (EVG) has shown notable TGA value as 418.6°C, as well burn-off test also shown that hybrid IPN composites have better wettability (less void presence) than all other laminates (EPGC-0.9%, VPGC-0.89%, EVGC-0.92%). Further, losses of physical strengths have been noticed on all specimens upon subjection on hygrothermal environment irrespective of IPN blend and fiber constituents.

In the fused deposition modeling (FDM) process, various thermoplastic filaments may be used as a feedstock material for the component fabrication. The present study involves incorporating a gyroid structure in wood/polylactic acid (PLA) polymer composite. The strength of the sample may reduce while incorporating lattice structure in PLA polymeric samples. There are certain difficulties due to the wide availability of process parameters that may vary the quality and strength during the fabrication of the sample through the FDM process. Determining the influence of certain important process parameters such as raster angle, layer thickness, and wall thickness is carried out in this research to attain higher mechanical strength and less dimensional error in the geometry of the fabricated sample. Taguchi L₉ orthogonal array is used in these experiments to optimize process parameters in the gyroid incorporated samples. The output responses in the present study are compressive strength and dimensional error. Both the output responses were predicted using the ANOVA technique. Both the output responses are greatly influenced by the raster angle with the value of 60.78% in compressive strength and 90.43% in the dimensional error, and Wall thickness is the least influenced process parameter with the value of 7.17% in compressive strength and 0.93% in dimensional error. The sequential order of influencing process parameters in both the compressive strength and dimensional error were raster angle > layer thickness > wall thickness. 31.019 MPa of compressive strength was observed in the confirmational compression test. The prepared composite can be used as a structural material in the replacement of balusters and handrails.

The focus of this research was to study how process parameters including fibre alignment, fibre length, fibre volume percentage and alkali pretreatment affected the mechanical and dynamic mechanical characteristics (DMA) of the sansevieria fibre composite. The nonwoven fabric was produced through the needle punching technique. 18 composite samples have been produced according to L18 Taguchi design. Four different process parameters were considered for investigation, such as fibre length, fibre volume fraction, the concentration of alkali and fibre alignment. Using Design S/N ratio analysis, the optimized process parameters for achieving maximum tensile, flexural and compression properties of the composite were measured. In the case of DMA analysis, three different parameters have been calculated only for selected samples such as storage modulus, loss modulus and loss factor. Variance analyses were carried out to measure the statistical influence of the process parameters on response. After this, validation of experiments was also done. SEM study was also carried out to understand the damage pattern of the composite sample.

The present study deals with the process optimization of printing parameters for fabricating gyroid TPMS (triply periodic minimal surface) lattice structure incorporated compression samples on the polylactic Acid polymeric material for obtaining the maximum compressive strength. The design of experiments is followed for the process parameter optimization. The experiment was carried out by varying three printing process parameters and four levels such as printing speed (10 mm/sec, 20 mm/sec, 30 mm/sec, and 40 mm/sec), layer height (0.10 mm, 0.15 mm, 0.20 mm, and 0.25 mm), and nozzle temperature (190°C, 200°C, 210°C, and 220°C). The L₁₆ orthogonal array is employed for the experimental procedure and the Taguchi optimization technique is utilized for the optimization of the printing process parameters for obtaining maximum compressive strength for the fabricated gyroid TPMS lattice structure incorporated compression samples. The experimental results confirm that printing speed and layer height have major influence of 57.28% and 30.92% on the compressive properties of the fabricated samples. Based on the regression analysis results, it can be concluded that the proposed mathematical model has observed an error percentage of 2.1% and a good fit has been observed with the experimental results. The macroscopic view of the fractured samples depicts that the sample fabricated at a nominal printing speed of 20 mm/sec and layer height of 0.10 mm has obtained the highest compressive strength and lower buckling during compression test. The optimized combination of printing process parameters for obtaining maximum compressive strength is 20 mm/sec, 0.10 mm, and 210°C.

Sustainable nano-composites refer to the development of composite materials that incorporate nano-particles or nanofibres in a matrix of sustainable polymers. These materials offer many benefits, including enhanced mechanical and thermal properties, improved resistance to degradation, and reduced environmental impact. Sustainable nano-composites have emerged as a promising class of materials and have received noteworthy consideration in recent years because of having unique characteristics and latent for numerous industrial applications. Nano-composites are composite materials that comprise a polymer matrix reinforced with nano-sized particles. Properties of sustainable nano-composites are characterized by their enhanced mechanical, thermal, and electrical properties compared to traditional composite materials. Nano-composites have been studied for several decades, and their applications are varied, including biomedical implants, energy storage devices, and high-performance structural materials. Industrial applications of sustainable nano-composites are expanding rapidly due to their improved properties and environmental benefits. Sustainable nano-composites have a wide range of industrial applications, including automotive, aerospace, electronics, packaging, and biomedical industries. Sustainable nano-composites represent a promising area of research and development for creating high-performance materials that are both environmentally friendly and economically feasible. Sustainable nano-composites are also a promising solution to address the environmental concerns associated with conventional nano-composites. The use of these materials is expected to increase in the future as sustainability becomes an increasingly important consideration in material design and manufacturing. This article provides an overview on the sustainable nano-composites.

Natural cassava pulp was selected as a bio-based reinforcement in plastic polymer composites to enhance mechanical and wetting properties as an eco-friendly product. This study developed reinforced polypropylene (PP) composites with cassava pulp (CP) to improve mechanical properties and wetting ability. The PP/CP specimens were fabricated via twin screw extrusion and injection molding. Tensile and flexural testing were performed using a universal testing machine, with wetting properties characterized by a contact angle goniometer. Incorporation of 10 wt% cassava pulp showed enhanced tensile strength (4.85%), Young’s modulus (14.38%) and flexural modulus (23.30%) compared with neat polypropylene, indicating higher stiffness of natural fiber-filled composites. Micropatterns were formed on the composite surfaces using the hot embossing technique. A superhydrophobic surface was achieved by designing micropattern geometry. Water contact angle of micropatterned neat polypropylene and polypropylene/cassava pulp composites increased compared to material with no pattern. Micropatterns on PP/CP composite surfaces can be used to develop new functional materials with high mechanical and superhydrophobic properties.

This study explores the synergistic effect of polycarbonate (PC), acrylonitrile butadiene styrene (ABS), and diglycidyl ether of bisphenol A (DGEBA) in reducing the inherent brittleness of epoxy resins. A 90/10 (90:10 proportion based on mass) composition of PC/ABS blended with DGEBA at 1.5 wt% modifier concentration demonstrated enhanced mechanical performance at both room and cryogenic temperatures. Comprehensive characterisation using FTIR, DSC, and optical microscopy confirms improvements in thermal stability and fracture resistance behaviour. Wear resistance is attributed to plastic deformation and tearing within the dispersed thermoplastic phase in epoxy matrix. For the case 90/10 blend with DGEBA, the impact strength of the modified DGEBA (m-DGEBA) matrix exhibited a maximum improvement of 20% at both room temperature (RT) and cryogenic temperature (CT). Rheology characteristics reveal an optimum viscosity rise of 0.2 Pa.s to 0.5 Pa.s, ensuring the optimal viscosity range of for infusion applications. This work presents a cost-effective and practical method for fabricating high-performance polymer composites suitable for advanced aerospace applications.

Hygrothermal environment has a significant impact on the safety and reliability of hybrid bolted-bonded composite joints. This study aims to investigate the effects of hygrothermal environment and geometrical parameters on the mechanical properties of hybrid bolted-bonded joints. In this paper, through the static tensile test and SEM scanning electron microscopy of hybrid bolted-bonded joints with different end-to-diameter ratios (E/D) and width-to-diameter ratios (W/D) under room temperature dry (RTD) and elevated temperature wet (ETW) environments, the change rule of the static strength of the joint and the macro-micro failure form are obtained. A finite element model of the hybrid bolted-bonded joint was established to obtain the initial stress distribution states of different layups and adhesive layers of laminates. The results indicate that the ultimate load of the hybrid bolted-bonded joint increases with the increase of E/D and W/D within a certain range. The ETW environment significantly reduces the ultimate load of hybrid joints. SEM scanning electron microscopy revealed that the compression damage of laminates in the ETW environment was aggravated. The hole edges exhibited an obvious state of matrix fracture and collapse. In the thickness direction, there was an increase in fiber breakage and debonding in the 90° fiber orientation, accompanied by more resin debris.

This study focuses on enhancing the tribological performance of polytetrafluoroethylene (PTFE) composites by incorporating graphene nanoplatelets (GNPs) through compression moulding technique. The main aim of the research was to investigate how varying weight percentages of GNP (1 wt %, 3 wt % and 5 wt %) influence the friction and wear properties of PTFE composites under both dry sliding and saline water environment. A significant reduction in the coefficient of friction (COF) and wear rate was observed with the addition of GNP, particularly in seawater. Specifically, the reduction of COF in sea water reached up to 58.765% with 3% of GNP compared to dry sliding. For wear reduction, a reduction of up to 90.247% was observed with 5% GNP in sea water condition. These findings reveal the potential of GNP-filled PTFE composites in applications requiring enhanced tribological properties in both dry and aqueous environments. The originality of this work lies in the comprehensive analysis of the environmental influence on GNP-filled PTFE composites, providing understandings of their applicability in marine environments.

Carbon fiber reinforced plastics (CFRP) are widely used in aerospace applications due to their high specific strength and design flexibility. However, significant subsurface damage often occurs during machining, which severely impacts the service life of the parts. In this paper, the influence of tool parameters and texture parameters on subsurface damage is comprehensively considered, and the Placket-Burman experimental design is used to screen the significance of these factors. Four key parameters that have great influence on the subsurface damage depth are determined: tool Angle, edge shape, texture width, and texture depth. Then, the response surface method is used to establish the prediction model of subsurface damage, and the optimal machining parameters to minimize subsurface damage are determined by combining the white whale optimization algorithm and the genetic algorithm. The experimental results show that the sub-surface damage is reduced by about 50% when using the optimized micro-braided tool compared with the traditional tool. These research results provide new ideas and methods for improving the machining quality of CFRP and optimizing tool parameters.

Glass fiber-reinforced polymers (GFRPs) made from thermoset polymers have been widely used across various industries. However, these composites have significant drawbacks, including poor interfacial adhesion between the fiber and matrix, as well as a substantial contribution to waste and environmental pollution due to the challenges in recycling, reprocessing, and reuse. Herein, firstly graphene oxide (GO) was incorporated in vitrimer matrix to fabricate recyclable vitrimer nanocomposites with improved interfacial interaction, high thermal stability, low dielectric constant, fast stress relaxation as well as rapid self-healing ability. The nanocomposite with 0.2 wt% GO is optimized to achieve excellent remoulding (89% of flexural strength) and self-healing (60 min for a 48 μm scratch) properties due to dynamic disulfide bond exchange mechanism. Furthermore, epoxy/GO matrix was used to develop glass fiber reinforced composites via vacuum assisted resin infusion molding process (VARIM). The developed composites demonstrate tremendous mechanical strength (250 MPa), shape-memory, weldability, and degradable properties. Due to the rapid chemical degradation of epoxy vitrimer under mild conditions in the thiol (2-mercaptoethanol and 1-otanethiol), facilitated by thiol disulfide exchange reaction, glass fibers (GFs) can be effectively recycled. The performance of recycled glass fibers closely matches that of original fibers, exhibiting nearly identical woven structure and mechanical properties. The single yarn of recycled glass fibers can achieve tensile strength of 85% (1-octanethiol) and 72% (2-mercaptoethanol) of the original glass fibers, thus, the recycling of glass fibers would be highly advantageous in terms of achieving the sustainability goals.

This study introduces a novel polyimide vitrimer ink specifically formulated for additive manufacturing on non-planar textile surface (i.e., Kevlar) substrates, aiming to advance the integration of strain sensors in aerospace and defense applications. The ink incorporates disulfide exchanges that enable reversible covalent adaptability, facilitating post-processing modifications and enhancing material recyclability. The synthesis involved a two-step process under nitrogen atmosphere, starting with the formation of polyamic acid (PAA) from 4-amino phenyl disulfide and pyromellitic dianhydride, followed by making the polymer UV-sensitive through the addition of a DMAEMA salt solution and a photoinitiator. Optimal printing parameters were established through experimental tuning of viscosity and modulus, enabling effective direct ink writing (DIW) on Kevlar. The printed sensors exhibited high sensitivity and durability under mechanical stress. Notably, the vitrimer’s disulfide linkages allowed for straightforward removal from substrates using a tailored solvent mixture, underscoring the potential for reusability and recycling in practical applications. This research demonstrates that polyimide vitrimers can be effectively used to create high-performance, adaptable, and recyclable sensors via additive manufacturing, providing a significant advancement in the field of smart materials for dynamic and harsh environments.