Bioinspired CFRP composites with improved impact resistance through coupling design

• The gradient design of CFRP composites is proposed for the first time. • Impact resistance is significantly improved by structural coupling and regulation. • The balance and synergy between delamination and deformation are revealed. • The G IC Init and G IC Prop are increased by 140.1% and 156.2%, respectively. • The relationship between penetration stage and failure mechanisms is elucidated. The low reliability of CFRP composites under impact loading seriously limits its application fields. In this work, bioinspired sinusoidal structures with a gradient design mimicking mantis shrimp’s dactyl club were introduced into CFRP laminates to improve the impact resistance. The effects of structural configurations and impact loading on the ballistic performance and energy absorption mechanism of biomimicking CFRP laminate were studied through transient response monitoring, non-destructive detection, interlayer fracture testing, and finite element analysis. The underlying relationship between the penetration stage and the failure mechanisms was analyzed. The results show that the ballistic limit and energy absorption rate (EAR) of CFRP laminates with sinusoidal-gradient coupling structure were significantly improved. The coupling structure increased the penetration distance of the projectile. By optimizing the wavelength and amplitude of the designed structure, the EAR of the CFRP laminates was greatly enhanced, achieving a balance and synergy between delamination and deformation. The optimized gradient structure not only increases the amount of secondary cracks, the efficiency of stress transfer, and the deflection angle of the projectile, but also increases the interlaminar fracture toughness by 156.2%, thereby improving the EAR of the laminate by 40.4% at an impact velocity of 191.8 m/s. Compared with spherical-nosed and conical-nosed projectiles, the CFRP laminate with gradient structure showed a higher EAR when hit by flat-nosed projectiles due to the large deflection and delamination region. The coupling structure with gradient design provides a novel way for the development of impact resistant CFRP composites. The effects of structure type, structure parameters and impact form on the ballistic performance and energy absorption mechanism of gradient-coupling laminate were studied by means such as transient monitoring, finite element analysis, interlayer fracture testing, and non-destructive detection.