Electromagnetic Wave-Absorbing and Bending Properties of Three-Dimensional Gradient Woven Composites with Triangular Sections

In order to solve defects such as poor integrity, delamination failure, and narrow absorption bandwidth, three-dimensional (3D) gradient honeycomb woven composites (GHWCs) with triangular sections were designed and prepared. Three-dimensional gradient honeycomb woven fabric was crafted with carbon fiber (CF) filaments and basalt fiber (BF) filaments as raw materials on an ordinary loom. Then, the 3D honeycomb woven fabric filled with rigid polyurethane foam was used as the reinforcement, and epoxy resin (EP) doped with carbon black (CB) and carbonyl iron powder (CIP) was conducted as the matrix. The 3D GHWC with triangular sections, which had both EM-absorbing and load-bearing functions, was prepared by the VARTM process. Through the macro test and micro characterization of 3D GHWCs with triangular sections, the overall absorbing properties and mechanical properties of the materials were analyzed. Moreover, the EM-absorbing mechanism and failure mode of the materials were clarified in this work. The results indicated that the CF filament reflective layer effectively improved the EM-absorbing and mechanical properties. Adding a CB/CIP-absorbing agent enhanced the overall EM-absorbing property but reduced the mechanical properties. The increasing number of gradient layers increased the maximum bending load, but the EM-absorbing performance first increased and then decreased. When the thickness was 15 mm, the maximum bending load was 3530 N, and the minimum reflection loss (RL_min) was -21.6 dB. The synergistic effects of EM-absorbing and mechanical properties were the best right now. In addition, this work provided a feasible strategy that adjusting the type of absorber and gradient aperture size ratio could meet the unique requirements of absorbing frequency and intensity, which has excellent application prospects in civil and military fields.