Search Results (388)

Flexible and wearable electronics require soft sensing materials that balance mechanical compliance, stable signal transduction, and durability for human–machine interfaces (HMIs). To address the limitations of single-filler systems, we propose a poly(vinyl alcohol) (PVA)/aramid nanofiber (ANF)/MXene organogel (PAM) as a multifunctional soft platform. This design integrates a PVA physically crosslinked network with ANF for mechanical reinforcement and MXene for electrical functionality. The optimized PAM composite exhibits outstanding mechanical properties, including a fracture stress of 2931 kPa, a fracture strain of 676%, and a fracture toughness of 9.04 MJ m⁻³. Importantly, PAM serves as a single material platform configurable into three sensing modalities. The resistive strain sensor achieves a gauge factor of 3.1 over 10–100% strain and enables the reliable recognition of human joint movements and gestures. The capacitive pressure sensor delivers a sensitivity of 0.298 kPa⁻¹, rapid response/recovery times of 30/10 ms, and is integrated with a wireless module to control a smart car. Furthermore, the PAM-based triboelectric nanogenerator (TENG) delivers excellent electrical outputs (V_oc = 123 V, I_sc = 0.52 μA, Q_sc = 58 nC) and functions as a self-powered smart handwriting pad, achieving a machine-learning-based recognition accuracy of 97.6%. This work demonstrates the immense potential of the PAM organogel for advanced, self-powered HMIs. Full article

The recycling of technical textile waste represents a major challenge due to the complex and multilayered structure of these materials. Firefighter protective clothing, mainly composed of high-performance aramid fibers combined with polymeric membranes and auxiliary textile components, is commonly landfilled or incinerated at the end of its service life, resulting in a significant environmental impact. This work utilized recycled aramid-rich textile waste obtained from end-of-life firefighter protective clothing as reinforcement for polyamide 6 to develop high-performance thermoplastic composites within a circular economy framework. Composites containing 15, 30, 45, and 60 wt.% of recycled textile waste were manufactured by melt compounding followed by injection molding. In addition, a selected formulation containing 30 wt.% reinforcement was compatibilized using an amino-functional silane to improve interfacial adhesion. The materials were systematically characterized in terms of tensile properties, thermal behavior, thermomechanical performance, water uptake, flammability, colorimetric properties, and fracture morphology by field emission scanning electron microscopy. The results revealed a pronounced increase in stiffness and thermomechanical stability, with tensile strength increasing from approximately 65 MPa for neat PA6 up to 78 MPa at 30 wt.% reinforcement, and elastic modulus exceeding 5000 MPa at high reinforcement contents. An optimal balance between mechanical performance and ductility was achieved at 30 wt.% reinforcement, while higher contents enabled a substantial extension of the service temperature range, with HDT values increasing from 55 °C for neat PA6 up to 173 °C for highly reinforced systems. FESEM analysis confirmed improved interfacial adhesion in silane-compatibilized systems, explaining the enhanced mechanical and thermomechanical behavior. Furthermore, the incorporation of recycled aramid-rich textile waste led to a significant improvement in flame retardancy, enabling UL-94 V-0 classification at 30 wt.% reinforcement and above, without the use of additional flame-retardant additives, enabling UL-94 V-0 classification without additional flame-retardant additives. Overall, this study demonstrates the technical feasibility and high added-value potential of valorizing firefighter protective clothing waste into advanced PA6-based composites with enhanced mechanical, thermal, and fire-resistant properties, providing a sustainable route for the valorization of high-performance textile waste. Full article

Conventional separators for lithium metal batteries suffer from poor thermal stability, flammability, and limited mechanical strength. In this study, we report a self-reinforced aramid separator integrated with Li₇La₃Zr₂O₁₂ (LLZO) via a sodium–naphthalene-based selective dissolution strategy. Controlled partial disruption of hydrogen bonding in copolymerized aramid enables the formation of a hierarchical structure consisting of intact fibers and nanofibrillar networks, thereby providing intrinsic mechanical reinforcement without binders. The separator maintains structural integrity up to ~400 °C and retains over 70% weight at 600 °C, exhibiting self-extinguishing behavior (LOI > 30). Puncture strength is more than three times higher than Celgard^®, while LLZO integration doubles the ionic conductivity along with excellent electrolyte wettability. This synergistic design provides a promising route toward intrinsically safe and high-performance lithium metal battery separators. Full article

Aramid fiber reinforced polymers (AFRPs) are widely used in aerospace and defense structures because of their high specific strength, impact resistance, and damage tolerance. However, severe burr formation during machining remains a major obstacle to achieving high surface integrity and dimensional accuracy. In particular, the mechanism by which tool edge radius affects burr formation in AFRP cutting has not yet been clarified quantitatively. To address this issue, this study develops an analytical model for the orthogonal cutting of AFRPs to reveal the burr formation mechanism associated with tool edge radius. The model, established on the basis of contact mechanics and fracture theory, predicts fiber deflection, cutting force evolution, fracture behavior, and burr length under different contact and boundary conditions. The results show that tool edge radius governs burr formation through a contact–state transition mechanism. When the edge radius is below a critical threshold, localized point-contact-like interaction promotes stress concentration and fiber fracture, leading to relatively clean material removal. When the edge radius exceeds this threshold, the interaction evolves toward extended contact and sliding, which suppresses complete fiber fracture and results in pronounced burr retention. Experimentally, increasing the edge radius from 5.6 μm to 110.3 μm increased the maximum burr height from 3.19 μm to 83.58 μm, corresponding to an increase of approximately 2520%. The predicted burr evolution agrees well with the experimental observations in both trend and characteristic magnitude. This study provides a mechanistic and predictive understanding of burr formation in AFRP machining and offers practical guidance for cutting edge preparation, tool wear control, and process optimization in high-quality composite machining. Full article

Thermal barrier materials play a crucial role in reducing heat transfer, suppressing thermal runaway (TR) propagation, and mitigating the risk of fire and explosion. Among the various types of thermal barrier materials, polymer-based thermal barrier materials, including polyimide (PI), aramid, epoxy resin (ER), polyurethane (PU), phenolic resin (PR), and silicone, have been widely applied in lithium-ion battery (LIB) safety protection owing to their excellent thermal stability, structural tunability, and favorable processability. This review provides a systematic and comprehensive overview of polymer-based thermal barrier materials for mitigating thermal runaway propagation in LIBs. The propagation pathways of TR in battery systems are first outlined to clarify the functional requirements of thermal barrier materials. Subsequently, representative classes of polymer materials are reviewed with emphasis on their structural characteristics and advantages. Strategies for enhancing thermal insulation, flame retardancy, heat absorption capacity, and mechanical robustness are then summarized in the context of thermal safety protection. Finally, key challenges associated with polymer-based thermal barrier materials are discussed, and future development directions are proposed. Full article

Polymer nanocomposites offer significant potential for improving the strength-to-weight ratio and dynamic behavior of drone blades. This study examines the vibration characteristics of tapered aramid (Kevlar)/epoxy composite blades reinforced with nanocarbon fillers—graphene (2D), multi-walled carbon nanotubes (MWCNTs, 1D), and fullerene (0D)—to determine the most effective filler for enhancing stiffness and operational stability. The laminated blades (300 mm length, 200 mm width, root thickness 13 mm, tip thickness 8 mm) incorporate ply drop-offs and a central honeycomb core. Modeling was performed using classical laminate plate theory integrated with the finite element method (FEM) in MATLAB (R2016a). Under clamped–free–free–free boundary conditions, the study considered rotational speeds of 750–2250 rpm, setting angles of 30–60°, various fiber orientations, and nanofiller contents of 0–10 wt.%. The results indicate that while the setting angle minimally affects natural frequency, it significantly influences damping in modes (1,2) and (2,1). Increasing nanofiller content improves stiffness, with optimal performance observed near 5 wt.%. At 1500 rpm in mode (1,1), MWCNTs provided the greatest enhancement. Overall, MWCNTs exhibited superior stiffness improvement and rotational stability compared to other fillers. Full article

The global textile industry, challenged by resource depletion and environmental pollution, urgently requires a shift toward a circular economy. However, recycling efforts remain limited, focusing mainly on conventional fibers and neglecting high-performance materials like aramid. This study addresses the recycling of used firefighting protective clothing-an aramid-rich, high-turnover waste stream typically landfilled or incinerated. Life cycle assessment reveals the significant carbon footprint of its production and disposal, underscoring the need for circular strategies. A systematic recycling framework is established, integrating collection logistics and redesign principles. A graded “three-tier” approach is proposed, enabling direct reuse, yarn regeneration, and non-woven production based on material conditions. High-value products were developed by incorporating firefighting heritage and intangible cultural crafts into the design, supported by digital product passports for traceability. These strategies enhanced market acceptance and emotional value. The work provides a scalable circular solution for high-performance textiles, aiming to extend material life, reduce carbon emissions, and advance sustainable textile management through a novel combination of technical recycling and cultural value addition. Full article

In the aviation industry the so-called ballistic impact of small accidental or human-made sources on aircraft elements during their service life encompasses several scenarios of practical interest. The experimental assessment of ballistic impact requires dedicated infrastructures (such as the light-gas gun system utilized in this study) and exhibits intrinsic difficulties, mainly concerning the proper acceleration of a projectile and the accurate measurement by a high-speed camera of its (inlet and outlet) velocity. As a first objective, this study aimed at characterizing the dynamic response of fiber metal laminates, manufactured ad hoc by the authors with two different stacking sequences currently not available in commerce. The layups included aluminum 2024 T3 and aramid fiber-reinforced prepregs, leading through specific treatments to excellent specific properties. The collision of the laminate with a 25 g, 9 mm radius steel sphere, traveling at speeds ranging from 90 to 145 m/s, caused a variety of scenarios: partial or complete penetration, with the projectile passing through and continuing its trajectory, remaining stuck in the sample (embedment) or even being bounced back (ricochet). The experimental information led to the estimation, for each typology of sample, of a conventional ballistic limit according to the Lambert-Jonas approximation, as a second objective, these data were utilized to validate an accurate heterogeneous model of the samples developed in the ABAQUS^® platform, discretized by finite elements in explicit dynamics and including geometric nonlinearity and contact. We describe plasticity and damage of the metal layers by the Johnson–Cook phenomenological model, progressive failure in the fiber-reinforced plies through a 2D Hashin criterion with damage evolution, and interlaminar debonding at multiple cohesive interfaces governed by the Benzeggagh–Kenane criterion. The outlet speed of the bullet measured during the experiments was retrieved correctly by this model, and a satisfactory agreement of the finite element predictions was found with the deformation patterns and the damage mechanisms identified by post mortem visual inspection. Finally, several discussion points are raised, concerning the robustness of the numerical analyses, the reliability of the constitutive modeling and the identification of the governing parameters. Full article

This study investigates the mechanical performance and blast resistance of high-performance aramid, carbon, and ultra-high molecular weight polyethylene (UHMWPE) fiber fabrics, responding to the need for lightweight and flexible materials in anti-explosion containers for aviation and critical infrastructure. The experimental methodology integrated quasi-static and dynamic tensile tests to characterize the strain-rate effect, followed by near-field air blast tests on both single-material and hybrid multi-ply fabric specimens to analyze their dynamic response, failure modes, and overpressure attenuation. Key findings revealed that carbon fabric exhibited high stiffness but was strain-rate insensitive and susceptible to brittle perforation failure, whereas aramid and UHMWPE fabrics demonstrated strain-rate sensitivity, with UHMWPE showing superior ductility and energy absorption. The hybrid multi-ply configuration (A-C-U sequence) achieved the least amount of failure, effectively utilizing the wave impedance of aramid fabric for initial shock reflection, high stiffness of carbon fabric for stress homogenization, and plasticity of UHMWPE fabric for energy dissipation. Additionally, all fabrics attenuated peak overpressure by over 80%, with enhancement observed for increased thickness. The study concludes that the strategic layering of different fabrics creates a synergistic effect, mitigating the weaknesses of individual fabrics and establishing an effective design paradigm for advanced blast-resistant structures, further enhancing the protective performance. Full article

Aramid paper serves as an insulating material in high-frequency power electronic transformers, and the incorporation of composite K-BNNS particles has been shown to enhance the insulating properties of aramid paper. Partial discharge (PD) is a predominant phenomenon that can lead to insulation failure in high-frequency transformers. Therefore, this paper primarily investigates the PD performances of different nanoparticle doping concentrations on aramid paper. Firstly, composite aramid papers containing K-BNNSs at different concentrations are prepared, namely 5%, 8%, 10% and 13%, respectively. Then, the experimental platforms of PD for composite aramid paper are established, and the PD performances, surface potentials, and hydrogen bonds under different high-frequency applied voltages are discussed. The experiment results show that the composite aramid paper with 10% K-BNNSs nanoparticle content has the optimal insulation performance. In the needle-plate and column-plate models, the PD amplitude decreases by 65.35% and 27.33%, respectively, when compared with non-doped aramid paper. Moreover, the breakdown voltage improves by 32.2% and 38.5%, respectively. After that, the influence mechanisms of residual charges and hydrogen bonds on the PD characteristics of composite aramid paper are analyzed. The results obtained in this paper can provide important reference for the design and selection of insulation materials for high-frequency transformers. Full article

Residual stresses are a persistent challenge in the additive manufacturing of composite parts by FFF (Fused Filament Fabrication) and can impair dimensional accuracy and mechanical performance. This article evaluates reflection photoelasticity (PhotoStress) as a full-field optical technique to visualize and compare residual-stress relaxation in ASA (Acrylonitrile Styrene Acrylate) reinforced with aramid fibers. The approach combines a controlled AWJ (Abrasive Water Jet) relief cut to induce local stress release with subsequent optical recording of isochromatic fringe fields using a reflection polariscope. Samples with thicknesses of 2–10 mm were manufactured and evaluated in two conditions: non-annealed and after annealing (80 °C/5 h). Under identical optical settings, no discernible isochromatic fringes were detected for 2–6 mm (Nmaxlobal < 0.60 in both conditions), whereas resolvable fringe patterns were observed for 8–10 mm. For 8 mm, the response was localized near the relief cut, with Nmax,global = 1.0 in the non-annealed condition and Nmax,global < 0.60 after annealing. For 10 mm, the response was more spatially extensive, and annealing reduced the global maximum from Nmax,global = 1.2 to 0.9. Taken together, these results demonstrate that reflection photoelasticity supports comparative full-field visualization of residual-stress relaxation in FFF composite specimens under fixed measurement conditions. In addition, an AWJ relief cut constitutes a practical and repeatable stress-release feature with limited additional thermal influence in the present configuration. Full article

Aiming at the problems of large cutting force, easy honeycomb tearing, and deformation during the traditional cutting process of aramid honeycomb materials and an increase in cutting temperature during continuous processing, which may lead to vibration stoppage, the ultrasonic cutting process characteristics of aramid honeycomb materials were studied. Firstly, torsional vibration was added on the basis of one-dimensional longitudinal ultrasonic vibration cutting (LUC), and the motion characteristics of longitudinal–torsional ultrasonic vibration cutting (LTUC) were analyzed. Secondly, a cutting simulation model was established using finite element simulation software. Under the same cutting parameters, the simulation results for the cutting force and cutting temperature of longitudinal ultrasonic vibration cutting and longitudinal–torsional compound ultrasonic vibration cutting were compared. Then, cutting experiments were conducted to verify the simulation results for cutting force, and single-factor experiments were used to analyze the cutting quality of aramid honeycomb under different processing methods. The results show that the three-directional cutting forces in longitudinal–torsional ultrasonic vibration processing are significantly lower than those in longitudinal ultrasonic vibration processing. The feed force decreased by an average of 28.2%, the tangential force decreased by an average of 45.8%, the axial force decreased by an average of 31.2%, and the tool temperature decreased by 21%. The processing quality of aramid honeycomb using longitudinal–torsional ultrasonic vibration cutting is better than when using longitudinal ultrasonic vibration cutting, which can more effectively reduce cutting stress, cutting force, and tool cutting temperature and show better process characteristics. Full article

To combat the critical hurdles of thermal buildup and low-temperature shutdown events in 5G-enabled smart wearables, a high-performance flexible composite film based on ellagic acid-modified single-walled carbon nanotubes (EA-SWCNTs) and aramid nanofibers (ANF) was designed and developed. The influence mechanism of the loading amount of the conductive network on the electrothermal properties of the composite material was focused on. The results show that through the π-π stacking non-covalent modification strategy, the uniform dispersion of EA-SWCNTs on the layer of ANF substrate and the construction of an ordered layered structure were successfully achieved. The prepared composite film could reach a steady-state temperature of 171 °C under a driving voltage of 3.5 V. In addition, it exhibits excellent electrothermal response characteristics and cyclic stability. It could reach the steady-state voltage within 10 s and shows no obvious performance degradation after multiple cycles. This composite film shows broad application prospects in fields such as intelligent wearable devices and flexible electronic protection. Full article

Water-lubricated bearings are critical components in marine propulsion systems, necessitating materials with exceptional tribological properties to ensure reliability. Filament-winding technology is an effective molding method for enhancing the comprehensive properties of polymers, and the selection of fiber materials has a significant impact on the performance of polymers. In this study, three types of polyurethane (PU) matrix filament-winding composites were fabricated via filament-winding technology. Under water-lubricated conditions, a friction test (disk-to-disk) with a duration of 2 h was performed, followed by systematic observations of the resultant wear behavior. The results indicate that aramid fibers exhibited the superior reinforcing effect on the PU matrix, effectively suppressing wear while enhancing mechanical properties. Specifically, under the conditions of 0.5 MPa-250 r/min (0.314 m/s), the minimum friction coefficient of the aramid fiber-wound composite material was 0.093, which was 57.73% lower than that of pure polyurethane. Under the conditions of 0.7 MPa-50 r/min (0.0628 m/s), the wear mass of the sample was limited to only 1.5 mg, which was 12% lower than that of polyurethane. This research can provide a practical reference for the application of filament-wound composite materials in water-lubricated bearings. Full article

Aramid-based polymeric fabrics are increasingly employed in lightweight protective and structural applications where high strength, flexibility, and impact resistance are required. Their response under high-velocity impact is governed by complex interactions among fiber properties, inter-yarn friction, and the mechanical behavior of the impacting body. In this work, three-dimensional finite element simulations were conducted in ANSYS Explicit Dynamics to investigate the coupled effects of the interfacial friction coefficient (μ = coefficient of friction = 0.0–0.5) and impactor material on the dynamic response of 24-layer plain-weave aramid panels. The numerical results reveal that low friction facilitates yarn mobility and localized penetration, whereas moderate friction enhances stress-wave dispersion and enables a more uniform activation of multiple fabric layers. At higher friction levels, penetration is further reduced, but localized stress concentrations may emerge due to constrained yarn movement. The constitutive properties of the impactor strongly influenced deformation modes and the efficiency of kinetic energy transfer to the composite structure. The simulated results are consistent with experimental data reported in the literature, confirming the predictive capability of the model. The study provides quantitative insight into the role of frictional interactions and impactor characteristics in optimizing the energy absorption and structural integrity of aramid-based polymeric fabrics subjected to high-velocity loading, contributing to the development of advanced lightweight protective materials. Full article