Xiaori Yang

Thermoplastic composites have a high application demand in aerospace, marine military and other cutting‐edge industry. However, it poses a considerable obstacle in achieving three‐dimensional (3D) thermoplastic composites because of the inadequate infiltration of highly viscous thermoplastic resins. In this paper, high‐toughness Polyetheretherketone (PEEK) resin‐based 3D orthogonal carbon fiber thermoplastic composites were designed and obtained. Low‐velocity impact test was conducted on 3D orthogonal woven composite (3DOWC) under the energy levels of 5 and 10 J, and its performance was compared with that of the 2D unidirectional layup composite (2DULC) and the 2D plain layup composite (2DPLC). The results showed that 3DOWC possessed superior elastic energy absorption capacity and less damage morphology compared to 2D composites. 3DOWC had the highest contact force value of 2420.25 N at 10 J, which is 36.83% higher than that of 2DPLC. Furthermore, a finite element model in multi‐scale was established to investigate the damage evolution and failure mechanism of the 3D orthogonal woven CF/PEEK composites. The damage morphology observed in both experimental and numerical findings demonstrated that the matrix shedding, while the yarn fractured on the nonimpact side beneath the impact point. Additionally, enhancing the tensile strength of the yarn in the bottom layer can lead to further improvement in impact resistance. This work provides an innovative method for manufacturing 3D thermoplastic composites and lays the foundation for the impact simulation analysis of such composites.Highlights: A novel approach was introduced for fabricating 3D carbon fiber/PEEK composites, which exhibits remarkable resistance to impact. A comprehensive investigation was conducted to evaluate the impact properties of 3D thermoplastic composite compared to 2D composite. A finite element model in multi‐scale including failure criteria was established to simulate the damage evolution.

Polymer composites with lightweight, ultralow dielectric constant, excellent thermal insulation and mechanical properties are in high demand in aerospace, transport, wireless communications and other fields. In this work, the three‐dimensional woven Kevlar/glass hybrid composites (3DKGC) with lightweight, high strength, excellent dielectric and thermal insulation properties were obtained with the Kevlar fiber and glass fiber as the raw materials. The results showed that the volume content of air in 3DKGC is over 82% and the volume density is as low as 0.29 g·cm⁻³, while the compression strength is as high as 7.68 MPa. 3DKGC exhibits an ultra‐low dielectric constant of 1.21. The wave transmission performance of 3DKGC was simulated using the CST software. The simulation results showed that 3DKGC has a return loss of 0.036 and a gain of 0.9982. Moreover, the 3DKGC provides superior thermal insulation than three‐dimensional woven Kevlar composites (3DKC) and conventional polystyrene foams. In summary, this work offers an attractive material that holds significant potential for application in aerospace, wireless communications and other fields where lightweight multi‐purpose composites are required.Highlights: 3D woven Kevlar/glass hybrid composites (3DKGC) were proposed and fabricated. 3DKGC exhibits low density of 0.29 g·cm⁻³ but high compression stress (7.68 MPa). 3DKGC possesses outstanding dielectric and thermal insulation properties. 3DKGC leverages the benefits of cost‐effectiveness and holistic functionality.

Three‐dimensional woven spacer composites (3DWSCs) with lightweight and excellent mechanical properties have promising application in communication, transportation, aerospace and other fields. However, traditional single‐layer 3DWSCs exhibit insufficient strength, especially when dealing with high thickness, as the pile yarns tend to buckle. In this study, inspired by the structural features of the Thalia dealbata, 3D woven integrated double‐layer glass fiber/epoxy resin spacer composites by mimicking were fabricated. Innovative integrated double‐layer structure design effectively improves the performance and failure mode of 3DWSCs under bending loads. Compared to single‐layer 3DWSCs, the resulting double‐layer 3DWSCs exhibited a 41.79% increase in peak bending load, a 46.85% increase in bending stiffness, and a 99.38% increase in energy absorption. In addition, the double‐layer 3DWSCs showed a low density of 0.52–0.55 g/cm³. This work introduces bioinspired double‐layer 3DWSCs with characteristics of lightweight and superior bending performance, potentially offering novel ideas for the design of high‐performance composites.Highlights: Inspired by the structural features of the Thalia dealbata, a 3D integrated woven double‐layer glass fiber/epoxy resin spacer composites by mimicking were fabricated. 3D woven double‐layer spacer composites are lightweight (0.52–0.55 g/cm³) and can effectively improve the bending properties of single‐layer structures. Based on the analysis of the fracture morphology, the significant improvement of the fracture pattern of the single‐layer structure by the double‐layer structure is effectively demonstrated. This study introduces novel design strategies for multi‐layer lightweight composite materials and holds broad applications.

In this work, a new type of epoxy foam‐filled 3D woven spacer composites (FF‐3DWSCs) was designed and manufactured by self‐made 3D loom and foaming technology. The low velocity impact behaviors, residual compressive properties and strengthening mechanisms of epoxy foam were systemically investigated. As the results, the FF‐3DWSCs showed higher impact load of 4000–5200 N than that of 3D woven spacer composites (3DWSCs) (2800–4300 N) at the energy from 10 to 40 J. The residual compressive strength of FF‐3DWSCs (23.85 MPa) was maintained at about 80% after 30 J energy impact. Due to the good compatibility of the epoxy foam and the epoxy resin and the synergistic effect between the pile yarn and the epoxy foam, the interface between epoxy foam and fiber/epoxy was strong. Therefore, the novel FF‐3DWSCs proposed here exhibited excellent impact properties and energy absorption capacity and can be used as a candidate material in the field of high‐performance composites.

In this study, to further improve the anti‐impact property of 3D woven spacer composites (3DWSC), three kinds of integrated 3DWSC with double‐layer cores assembled at different height combinations of 4 + 8 mm, 6 + 6 mm, and 8 + 4 mm, were designed and prepared. And the impact performances and the post‐impact lateral compressive properties of the resulting composites were investigated and compared to the single‐layer 3DWSC of the same height. The results show that among the three combinations, 3DWSC‐4 + 8 has the highest contact force value of 2454.33 N at 10 J, which is 90.60% higher than that of single‐layer 3DWSC. And the residual compressive strength of 3DWSC‐4 + 8 maintains 91.30% after 10 J energy impact, while the retention value of single‐layer 3DWSC is only 68.43%. The above results can be attributed to the fact that the addition of the middle panel in double‐layer 3DWSC is benefical to improve the capacity of the material to withstand transverse load or bending moment and to absorb more energy through its damage compared to the single‐layer 3DWSC. In addition, the SEM images showed that only resin cracks in the double‐layer 3DWSC and no fiber breakage and delamination, indicating exceptional mechanical stability of the as‐prepared double‐layer 3DWSC. This work can serve as a reference for the design and fabrication to multi‐layer 3DWSC, a promising material in the field of high‐performance composites.