Search Results (526)

Battery housings are critical structural and safety components in electric vehicles, fulfilling multiple functions related to mechanical protection, crashworthiness, thermal management, fire resistance, electromagnetic shielding, and integration of battery modules into the vehicle body. While metallic housings, particularly aluminum and steel, remain dominant in industrial applications, increasing attention is being given to composite materials as lightweight alternatives capable of improving energy efficiency and extending driving range. However, the growing use of composites in battery enclosures raises important questions regarding recyclability, end-of-life management, and compatibility with circular economy principles. This review critically examines the current state of the art in composite materials used for electric vehicle battery housings, with particular emphasis on glass- and carbon-fiber-reinforced thermoplastics, thermoset composites, sandwich structures, and hybrid multi-material systems. The paper discusses the functional requirements imposed on battery housings and analyzes how these requirements influence material selection and design strategies. Particular attention is devoted to recycling pathways applicable to composite battery enclosures, including mechanical recycling, thermal treatment, chemical recycling, and reuse-oriented approaches, as well as to the limitations associated with mixed-material assemblies, adhesives, coatings, and integrated functions. The review also addresses circular design strategies for battery housings, including design for disassembly, material traceability, modularity, and the incorporation of recycled polymers and secondary reinforcements into new housing systems. Current research gaps are identified in the integration of structural performance, fire safety, manufacturability, and recyclability within a single design framework. The analysis shows that thermoplastic composites currently offer the most promising route toward circular battery enclosures, while thermoset-based systems still face significant challenges in high-value recycling. The paper concludes by outlining future research directions required for the development of lightweight, safe and recyclable composite battery housings aligned with sustainable mobility and circular economy goals. Full article

Ground vibration testing (GVT) plays a key role in the validation of numerical models and the assessment of aeroelastic stability in lightweight aircraft structures. This study presents an experimental and numerical investigation of a full-scale composite flying wing unmanned aerial vehicle (UAV) intended for vertical take-off and landing operations. Due to its low structural mass and highly integrated configuration, the aircraft exhibits increased sensitivity to modeling assumptions, boundary conditions, and measurement uncertainties. A finite element model was developed in Ansys, incorporating detailed laminate definitions and the internal sandwich structure. Experimental modal testing was performed under free-free boundary conditions using an electrodynamic shaker and a distributed measurement consisting of 94 response locations. Frequency Response Functions (FRFs), coherence analysis, and the Complex Mode Indication Function (CMIF) were employed to identify the dominant structural modes. Particular attention was given to the bending and torsional modes that govern aeroelastic behavior. Comparison of experimental and numerical results showed good agreement in mode shapes, while discrepancies in natural frequencies ranged from 10.4% to 20.1%. The results demonstrate that the model adequately captures the dynamic behavior of the aircraft and provides a reliable basis for future aeroelastic and flutter analyses of lightweight composite flying wing. Full article

The valorization of post-consumer waste materials is an important strategy for reducing environmental impact and supporting circular material use. In this study, lightweight sandwich composites were developed using recycled paper and cardboard as core materials, producing sustainable panels for thermal and acoustic insulation. Core panels were manufactured from 100% paper, 100% cardboard, and a 50–50% paper–cardboard mixture. Environmentally friendly foaming agents were added to increase porosity and reduce density. The cores were subsequently combined with 3 mm medium-density fiberboard (MDF), 1 mm oak veneer, and date palm midrib fibers to provide different surface characteristics. The resulting sandwich composites were evaluated through standardized measurements of thermal conductivity and sound absorption coefficients. Microstructural characteristics were investigated using stereomicroscopy and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDX). The results indicate that both the core composition and the type of face layer influence their performance. Whilst composites with cardboard-rich cores had higher porosity and better thermal insulation, introducing perforations and increasing the panel thickness improved sound absorption. The findings demonstrate that recycled paper and cardboard can be effectively used as sustainable raw materials to produce lightweight sandwich composites, tested at material scale, for non-structural interior insulation/acoustic panels. Full article

To address prevalent industrial challenges, including the high cost of fabricating microstructures via photolithography and 3D printing, impurity residues easily generated by conventional physical/chemical pore-forming techniques, and the limited sensitivity of regular capacitive sensors, this paper innovatively proposes an integrated low-temperature in situ gas foaming strategy using ammonium bicarbonate for the fabrication of porous TPU-based ionic gels. Relying on the complete gaseous decomposition property of ammonium bicarbonate upon heating, a three-dimensionally interconnected continuous porous network is spontaneously constructed inside the polymer matrix. Thermoplastic polyurethane (TPU) is selected as the continuous polymer phase, and [EMIM][TFSI] imidazolium ionic liquid is blended as the ion source to synthesize composite ionic gel substrates. A PDMS composite slurry filled with graphene is employed to prepare flexible substrates, followed by low-temperature oxygen plasma surface modification to introduce polar functional groups such as hydroxyl and carboxyl onto electrode surfaces. A standard sandwich-structured ionic pressure sensor with the configuration of “top modified electrode—porous ionic gel dielectric layer—bottom modified electrode” is finally assembled. The porous framework and modified electrodes constitute a dual synergistic enhancement system: the porous structure markedly reduces the equivalent elastic modulus of the gel and improves its compressive deformation capacity; polar-modified electrodes optimize the interfacial compatibility between electrodes and gels, shorten ion migration paths and lower interfacial contact resistance. Systematic calibration of multiple batches of parallel samples reveals that the as-fabricated sensor achieves a high sensitivity of 25.3 kPa⁻¹ across the full measuring range from 0 to 1000 kPa with a linear fitting coefficient R² = 0.992. The loading response time and unloading recovery time of the device are 60 ms and 80 ms respectively, with a performance degradation of less than 3% after 1000 consecutive loading–unloading cycles, featuring low hysteresis error and excellent signal repeatability. Multi-scenario in vivo wearable tests on human subjects verify that the device can precisely capture subtle fluctuations of radial artery pulse and periodic laryngeal deformation during swallowing, distinguish characteristic waveform patterns of various English words according to differences in vocal cord vibration, and accurately detect bending motions when attached to finger joints. The entire fabrication process adopts common chemical raw materials and standard laboratory equipment without expensive micro-nano processing facilities, featuring convenient raw material procurement and high process fault tolerance, which enables large-area coating-based mass production. This work delivers a novel technical route for the low-cost large-scale production of high-performance ionic flexible sensors and bears significant industrialization reference value for applications in wearable medical monitoring, bionic robotic electronic skin, flexible human–machine interactive touch panels and other related fields. Full article

To address safety issues caused by the bottom impact of the power battery in new energy vehicles, a lightweight bottom panel design scheme based on long glass fiber-reinforced polypropylene (LGF/PP) honeycomb composite was proposed. By employing the sandwich structure with an LGF/PP surface material/polypropylene honeycomb core combined with high-shear-strength structural adhesive bonding technology, ball impact protection for the power battery bottom is greatly improved. A ball striking test was carried out in accordance with the requirements and test methods of bottom anti-collision for pure electric passenger vehicles (T/CSAE 244-2021), and the performance differences of traditional steel bottom guards were compared. The results show that the optimized honeycomb composite bottom guard plate (surface thickness 1.3 mm/honeycomb core 8 mm) is able to reduce the deformation of the aluminum plate to 10.4 mm, resulting in deformation that is only 68% of that observed with the steel bottom guard plate while achieving a 43% reduction in weight. The deformation of the aluminum plate was further reduced to 42.3% with the introduction of a structural adhesive with a 5 MPa shear strength. In addition, the honeycomb structure exhibits controllable plastic deformation after impact, while the steel bottom guard plate is severely distorted but not ruptured, highlighting the damage tolerance and energy absorption advantages of the composite material design. The honeycomb composite bottom guard plate outperforms the traditional scheme in terms of light weight, protection performance and cost. This work contributes to the field of power battery bottom protection. Full article

In this study, free vibration analysis of three-layer sandwich panels with cores based on a triply periodic minimum surface (TPMS) and graphene platelet-reinforced composite (GPLRC) faces is performed. Four different geometries including cylindrical, spherical, saddle and flat panels were investigated and the governing equations were solved using higher-order shear deformation theory (HSDT) extracted from Hamilton’s principle. The accuracy and precision of the presented analytical method is verified by comparing the dimensionless natural frequencies with reference studies. Then, the effect of various parameters including panel geometry, core topology type and graphene weight percentage on the vibration response was investigated. The results show that adding graphene to the face layers significantly increases the natural frequencies and improves the overall stiffness of the structure. In addition, the frequencies of the panel may be controlled through different patterns and topologies. Also, double-curved panels, especially spherical geometries, present the highest fundamental natural frequency. The findings of this research could play an important role in the design and performance evaluation of advanced structures with TPMS cores and nanoscale reinforcement. Full article

Lithium-ion batteries with high energy density and long cycle life have been widely used as secondary batteries in electric vehicles and energy storage systems. With the growing demand for high energy density in lithium-ion batteries, silicon-based materials, which possess a high theoretical specific capacity (4200 mAh g⁻¹), are regarded as core candidates for anode materials. However, Si-based materials undergo severe volume expansion (up to 300%), which leads to the collapse of the electrode structure, inducing pulverization of the active material and capacity loss, thereby hindering the commercial application of silicon-based materials. To address these issues, scholars from various countries have developed many silicon-based materials with different compositions and three-dimensional structures, and have made some research progress. This review first elaborates on the lithium storage mechanisms and advantages of diverse silicon-based anode materials by taking Si, SiO_x, SiN_x, and SiP_x as representative examples with distinct characteristics. Subsequently, from the two aspects of dimensional design (0D, 1D, 2D and 3D) and architecture design (core–shell, sandwich-like and network structure), the design strategies for various silicon-based anode structures and their enhancement on electrochemical performance are analyzed. Finally, this review elucidated the challenges faced by silicon-based anodes from the perspectives of mechanism elucidation, structural customization, industrialization, and full-cell applications. It also proposed future development directions for silicon anodes by combining actual challenges and focusing on aspects such as structure optimization, machine learning, advanced characterization techniques, and mechanistic analysis. Full article

Designing lightweight composite sandwich structures is challenging due to the conflicting objectives of minimizing structural weight and cost while satisfying strength and stiffness requirements. The optimization procedure becomes more complex when multiple discrete design variables and nonlinear material behavior are involved. This study presents a newly developed optimization methodology for a sandwich structure composed of Fiber Reinforced Polymer (FRP) laminated facesheets and an aluminum honeycomb core. To reduce the computational cost associated with repeated high-fidelity Finite Element (FE) analyses, a surrogate modeling strategy based on Artificial Neural Networks (ANNs) is employed to approximate the structural response. The applied dataset is generated using Monte Carlo simulation in which combinations of design variables are used as inputs, and the corresponding structural responses obtained from the analytical formulation are used as outputs for training the ANN surrogate model. The trained ANN model is integrated with a Multi-Objective Niching Memetic Particle Swarm Optimization (MO-NMPSO) algorithm to simultaneously minimize structural weight and material cost while satisfying constraints on facesheet strength, wrinkling, intra-cell buckling, deflection, core shear failure and structural thickness. The resulting Pareto-optimal solutions are validated through detailed FE simulations, demonstrating the reliability of the newly elaborated optimization framework. The results of the newly developed computationally efficient optimization procedure provide a diverse set of optimal design solutions for the investigated sandwich structure. Full article

This study investigates the energy absorption capacity of large three-honeycomb cell cores of different geometrical configurations, focusing on the influence of the constructive parameters on their impact response. The analyzed sandwich structures were additively manufactured using Onyx (a nylon-based composite) for the core cells and integrated into an assembly consisting of 6060-aluminum face sheets and encapsulated within a 6060-aluminum tube. These configurations represent a realistic engineering solution for lightweight structures designed for energy absorption. The analyses were conducted for two impact energy levels, 20 J and 50 J, enabling the evaluation of the structural sensitivity to different dynamic loading conditions. The results indicate a significant reduction in peak force with an increasing number of cells along the height. Compared to the single-cell configuration, the peak force decreases by approximately 15% for the two-cell configuration and 22.5% for the three-cell configuration, corresponding to a reduction of roughly 9% between the two- and three-cell cases. These findings highlight the critical role of geometry in optimizing the impact performance of honeycomb structures and provide relevant insights for the design of additively manufactured energy-absorbing crush-type components in engineering applications. Full article

This study investigates the fatigue behaviour of sandwich composite materials under three-point bending. A stiffness reduction approach was adopted to model the damage evolution as a function of fatigue cycles. However, existing studies often rely on extensive experimental campaigns or focus on isolated damage indicators, without providing a unified and efficient framework for predicting fatigue life under displacement-controlled bending. Empirical functions, fitted to experimental data, allowed the prediction of fatigue life while minimizing the need for extensive testing. Wöhler curves were constructed to compare experimental results with analytical predictions. Damage accumulation models were developed to describe stiffness degradation and damage kinetics. These models were experimentally validated and applied to simulate load evolution, fatigue life, energy release rate, and damage progression in sandwich composites. A good agreement was achieved between experimental data and model predictions, confirming the reliability of the proposed approach. Full article

This study experimentally investigates the structural behavior of hexagonal- and square-shaped composite specimens subjected to vertical compression, vertical tension, and diagonal tension loading. The specimens were fabricated using four- and six-layer alkali-resistant (AR) glass textile reinforcements embedded in a modified cementitious mortar via pull, pour, and roll manufacturing techniques. The mechanical performance of polyvinyl alcohol (PVA) fiber-reinforced composite connectors and steel clamp-type elements was also evaluated at the joints of hexagonal specimens under vertical tension and lateral shear loading. The results show that increasing the number of textile layers significantly enhances structural performance. A 50% increase in textile layers improved load-carrying capacity by up to 56% in compression, 104% in tension, and 216% in diagonal tension. Corresponding increases of approximately 20–42% in ductility and up to 266% in energy dissipation capacity were observed. No failure occurred in the connecting elements, confirming their adequate stiffness, strength, and ductility. In addition, validated three-dimensional finite element models were developed to simulate the response of the hexagonal specimens. Overall, the proposed system demonstrates strong potential for applications such as infill walls, cladding, and sandwich panels due to its favorable strength, ductility, and energy absorption capacity. Full article

In recent years, environmental sustainability has become a key issue in the shipbuilding industry, driving research towards a reduction in the environmental impact throughout the entire life cycle of vessels. In this context, composite materials are a solid alternative to achieve mechanical performance optimization and energy consumption reduction. This study compares two hull configurations, one in a glass fiber-reinforced thermoset composite and one in a thermoplastic composite sandwich structure, through life cycle assessment. The aim is to assess the influence of material choice and structural configuration on overall environmental impacts by analyzing energy and material inputs and emissions throughout the entire life cycle, from “cradle to grave” excluding the end-of-life treatment. The results evidence a 36% average reduction in the impact categories analyzed. Moreover, economic benefits emerged, with a 35% reduction in the cost of energy required during the analyzed life cycle phases and 9% reduction in the material supply. This work aims to contribute to the definition of more sustainable design strategies to produce hulls and naval components, promoting a transition towards a more efficient and environmentally friendly nautical sector. Full article

Steel-concrete-steel composite (SCS) panels have been extensively utilized in structural engineering and are vulnerable to impact loading during their service life. Therefore, this work numerically and theoretically investigated the low-velocity impact performance of SCS panels. Firstly, based on the existing drop-hammer impact experiments, three-dimensional finite element (FE) models incorporating material failure and strain-rate effect were constructed using ABAQUS and employed to predict the dynamic responses of SCS panels subjected to impact loading. After verifying the reliability of numerical models with test results, the impact-resistant mechanism of these members was analyzed. Then, a parameter analysis was carried out to systematically explore the influences of essential parameters on the impact responses of SCS panels. Results indicated the sandwiched concrete played a predominant role in absorbing impact energy. The proportion of plastic energy absorbed by the concrete reduced by approximately 11% with increasing impact height from 3.0 m to 4.5 m. The steel plate ratio had a marginal effect on the impact response under the constant panel thickness, while the variations in impact velocities, boundary conditions, and axial-load levels significantly affected it. As the axial load ratio reached 0.6, the instability occurred due to severe buckling of steel faceplates. Finally, an empirical formula for calculating the local bulging stiffness of bottom steel faceplate was proposed. The revised calculation method was able to accurately predict the post-peak mean force and the mid-span deflection of bottom steel faceplate. Full article

Flat leather belts were the first to be used in drive and transport technology and were later replaced by plastic belts. Recently, there has been a return to hybrid designs, where belts are constructed as a “sandwich” with a technical leather outer layer and a polyamide or TPU inner core. This study analyses the thermal behavior of a modern leather belt transmission as a function of braking torque at different rotational speeds of the active pulley. A linear temperature response was observed, with temperature differences between the passive and active belts of 4 °C at 500 rpm (R² = 0.93), 5.4 °C at 1000 rpm (R² = 0.96), and 4 °C at 1500 rpm (R² = 0.98). Due to the specific structure of the outer layer, non-contact surface measurement methods were applied. Surface topography analysis showed only minor changes in average roughness, with Sq = 37.8 µm (new belt) and 37.9 µm (used belt) and Sa decreasing from 26.5 µm to 25.1 µm. However, clear morphological changes were observed: Ssk decreased from 2.63 to 2.00, Sku from 14.3 to 8.19, Sp from 449 µm to 308 µm, and Sz from 557 µm to 400 µm, indicating reduced peak sharpness after wear. Profile parameters increased after operation, with Ra rising from 18.6 µm to 21.9 µm, Rq from 26.7 µm to 30.7 µm, and Rz from 116 µm to 143 µm. Microscopy confirmed wear-related smoothing and fragmentation of surface asperities. The results demonstrate that the applied methods are effective for evaluating thermal response and wear mechanisms in modern leather composite belts. Full article

To improve the durability of terahertz (THz) electromagnetic shielding materials in atomic oxygen environments relevant to low Earth orbit (LEO), two MXene/para-aramid nanofiber (ANF) composite architectures were designed, including a uniformly blended structure and a sandwich configuration. Ti₃C₂T_x MXene was used as the conductive phase, while ANF served as a protective matrix. Oxygen plasma treatment was employed to simulate atomic oxygen exposure. The results show that the plasma resistance of blended films strongly depends on MXene content. Increasing the MXene fraction enhances conductive network redundancy and reduces conductivity degradation. In contrast, the sandwich-structured film exhibits superior structural stability. The outer ANF layers effectively limit direct plasma–MXene interaction and undergo surface carbonization during plasma exposure, forming an additional diffusion barrier. As a result, the sandwich film maintains stable THz shielding performance, with the average shielding effectiveness increasing from 42.6 dB to 44.9 dB after plasma treatment. These results indicate that structural regulation of the internal conductive network, which limits plasma penetration, is essential for maintaining stable MXene-based THz shielding performance under oxidative plasma conditions. Full article