Enhanced impact resistance of three-dimensional woven composites with double-layer core structure

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.