Numerical simulation on fracture mechanisms of CFRP with barely visible impact damage by hail impact

This work studied the barely visible damage caused by hail impact on the aircraft surface's carbon fiber-reinforced polymer (CFRP) plates. The mesoscale model of the composites was established. Puck criterion combined with the modified Tsai-Wu polynomial criterion was used as the criterion of the fiber bundle fracture failure in numerical simulation. According to the computerized tomography three-dimensional reconstruction results and the test results of impact response obtained from previous work, the reliability of numerical simulation was verified. It was shown that different stress states cause different fiber fracture modes. Moreover, the location with the largest crack density was not at the center of the impact area but at the edge where the ice projectile contacted the CFRP plate at the moment of ductile–brittle transition during the impact. Finally, based on the influence mechanism of the fiber bundle's fracture mode on the damage propagation of the internal structure, the damage threshold of composites was determined to be about 4.872 J. This work provides a method to explain the generation mechanism of barely visible impact damage and judge the overall failure of CFRP.