Experimental investigation on the damage accumulation mechanism of 3D orthogonal woven composites under repeated low-velocity impacts

This paper presents an experimental investigation into the response of carbon fiber reinforced composites with various fiber architectures to repeated low-velocity impacts. Mechanical response diagrams, including repetition numbers and damage morphologies of the composite samples, are provided. Varied energy levels (20J, 35J, 50J) and impact numbers (up to 30th) are considered to induce perforated damage in the composite samples. It is found that the mechanical responses of the composite samples under repeated impact events exhibit distinct characteristics in terms of impact threshold and stiffness degradation. The 2D unidirectional (2DUD) laminated composite sample exhibits a high impact threshold during impact events but stiffness rapidly decays after an initial substantial decline. The 2D plain woven (2DPW) laminated composite sample accumulates impact damage at both high and low levels, resulting in a gradual stiffness decrease during impact events. In addition, the 3D orthogonal woven (3DOW) composite sample demonstrates a higher impact threshold with its stiffness gradually decreasing under high-level impacts. In contrast, both 2DUD and 2DPW composite samples exhibit extensive plastic deformation of the resin matrix with minimal fiber fracture, enabling efficient dissipation of impact energy. Conversely, the 3DOW composite sample primarily dissipates impact energy through fiber fracture. Additionally, it is noteworthy that while both 2DUD and 2DPW composites demonstrate enhanced robustness against repeated impacts at low-energy levels, a significant improvement in durability is observed specifically for the 3DOW composite under high-energy level impacts.