Low-velocity impact damage of bionic turtle shell sandwich laminates with different suture shapes

Turtle shells have evolved over millions of years, developing exceptional mechanical properties such as high relative strength and toughness, rendering them highly effective in resisting impacts. This study delves into the impact resistance of bionic turtle shell structures with various suture shapes. This article analyzes the low-velocity impact of carbon fiber epoxy resin prepreg (CF/EP) composite sandwich panels with a suture interface by using the finite element simulation. The simulations encompass closed and unclosed models featuring bonded and unbonded tips, each with diverse trapezoidal geometries (triangular, trapezoidal, anti-trapezoidal, and rectangular). The findings reveal that sandwich structures with suture interfaces demonstrate significantly enhanced impact resistance compared to those lacking sutures, displaying 3–9 times greater deformation capacity and 20–30 times higher energy absorption capacity. The impact resistance of the triangular suture interface exceeded that of other bioinspired suture shapes, with trapezoidal and anti-trapezoidal sutures also enhancing stiffness, strength, and toughness. Additionally, a 6° bonded tip angle resulted in optimal performance for the triangular suture interface across all analyzed perspectives. The simulation study in this paper provides comprehensive and reliable data on low-velocity impact results, offering fundamental insights for researchers to design composite material structures that meet specific mechanical requirements effectively. Additionally, it offers novel ideas for the connection of protective structures, such as artificial armor.