Damage and perforation resistance behaviors induced by projectile impact load on bonding-patch repaired and scarf-patch repaired composite laminates

A three-dimensional continuum damage model is proposed to analyze the damage and perforation resistance behaviors of bonding-patch and scarf-patch repaired composite laminates under projectile impact load. Coupling with modified 3D-Hashin failure criteria, a linear-exponential law due to fiber pull-out failure and an exponential law are used to predict tensile and compressive softening processes of materials, respectively. A cohesive interaction based on triangle traction–separation law and mixed-mode fracture energy method is applied for interface debonding damages between patch/lamina, patch/patch and lamina/lamina. Comparisons are made between numerical results and several available test data for different impact offsets. The perforation resistance and interface debonding damage mechanisms are extensively discussed using finite element analysis. Further, perforation resistance behaviors of laminate with six different patch-repair patterns are assessed. Effects of initial velocity of projectile on residual velocity and energy-absorption are discussed. A residual velocity error within 7.3% and energy-absorption error within 9.2% is found between simulations and tests. Consistent failure modes including fiber fracture, matrix cracking, delamination and interface debonding are also identified. As the projectile invades patches, interface debonding damage in patches is accumulated rapidly, especially for larger impact offset. The combined patch-repairs show a reduction of at the most 48.3% in velocity and higher ballistic limit velocities which implies better perforation resistance capacity. The energy-absorption almost increases with increasing the initial velocity and a decreasing trend in average energy-absorption is found with the increase of impact offset.