Biomimetic construction of 3D needle-punched CF/PEEK composites based on ladybug forewing structure for directional reinforcement

3D needle-punched CF/PEEK composites are a kind of composites with promising applications in multiple fields, such as implant materials, but their mechanical properties in the Z-axis and interlaminar are still weak at present. In this study, a bio-inspired reinforcement structure based on ladybug forewing was developed to achieve directed reinforcement of 3D needle-punched CF/PEEK composites. Carbon fiber yarns were stitched into the 3D needle-punched CF/PEEK preforms according to the set structure, and the bio-inspired CF/PEEK composites were obtained after hot pressing. The interlaminar and in-plane mechanical properties of the composites were investigated at different stitch lengths. The results showed that the addition of the bio-inspired structure greatly improved the interlaminar shear strength of the composites, reaching 111.30 MPa, an enhancement of 95.06%. The in-plane mechanical properties, including tensile, flexural, and compression, were also significantly improved to different degrees. The “structure-effect” relationship in the bio-inspired CF/PEEK composites was investigated, and the effectiveness of such a bio-inspired reinforcement structure was demonstrated. This new reinforcement strategy provides a new idea for the improvement of the mechanical properties of multi-stage carbon fiber-reinforced thermoplastic resin matrix composites. Highlights The in-plane and interlaminar mechanical properties of composites were simultaneously improved. Up to 95.06% improvement in interlaminar shear strength. A novel bionic strategy of directional reinforcement was developed. The “structure-effect” relationship in the composites was investigated.