Translaminar fracture toughness of bionic laminates incorporating a bi-sinusoidal helicoidal structure under tensile loading

Translaminar fracture toughness is a critical mechanical parameter that determines the damage tolerance, notch sensitivity, and overall structural integrity of carbon fiber reinforced polymers. Inspired by biological systems, a bi-sinusoidal helicoidal structure exhibiting exceptional damage tolerance has been identified in the mandible of the trap-jaw ant ( Odontomachus monticola ), offering valuable insights into mechanisms of energy dissipation and crack deflection. A bionic laminate (BL) incorporating this bi-sinusoidal helicoidal structure was designed and fabricated using unidirectional carbon fiber prepregs through a mold press-forming technique. Compact tension tests were conducted to evaluate the translaminar fracture toughness of the laminates. The results reveal that introducing the bi-sinusoidal helicoidal structure significantly enhances the translaminar fracture toughness and energy absorption capacity of the laminates compared with traditional flat counterparts. Specifically, the critical fracture energy of the bionic laminate (BL 5 ) increased by 70.6% relative to that of the traditional laminate (TL). The critical fracture energy of bionic laminates decreases with the increasing wavelength of the sinusoidal structure. This improvement is attributed to geometrically induced crack deflection, crack branching, and localized energy dissipation along the sinusoidal interfaces. These findings offer a promising design strategy for developing next-generation composite materials with superior damage tolerance and fracture resistance.