2D Plain and 3D Needle-punched C/SiC Composites: Low-velocity Impact Damage Behavior and Failure Mechanism

Continuous carbon fiber reinforced silicon carbide (C/SiC) composites are often subjected to low-velocity impacts when utilized as structural materials for thermal protection. However, research on in-plane impact damage and multiple impact damage of C/SiC composites is limited. To investigate the in-plane impact damage behavior of C/SiC composites, a drop-weight impact test method was developed for strip samples, and these results were subsequently compared with those of C/SiC composite plates. Results show that the in-plane impact behavior of C/SiC strip samples is similar to that of C/SiC composite plates. Variation of the impact load with displacement is characterized by three stages: a nearly linear stage, a severe load drop stage, and a rebound stage where displacement occurs after the impact energy exceeds its peak value. Impact damage behavior under single and multiple impacts on 2D plain and 3D needled C/SiC composites was investigated at different impact energies and durations. Crack propagation in C/SiC composites was studied by computerized tomography (CT) technique. In the 2D plain C/SiC composite, load propagation between layers is hindered during impact, leading to delamination and 90° fiber brittle fracture. The crack length perpendicular to the impact direction increases with impact energy increases, resulting in more serious 0° fiber fracture and a larger area of fiber loss. In the 3D needled C/SiC composite, load propagates between the layers during impact through the connection of needled fibers. The fibers continue to provide substantial structural support, with notable instances of fiber pull-off and debonding. Consequently, the impact resistance is superior to that of 2D plain C/SiC composite. When the 3D needled C/SiC composite undergoes two successive impacts of 1.5 J, the energy absorption efficiency of the second impact is significantly lower, accompanied by a smaller impact displacement. Moreover, the total energy absorption efficiency of these two impacts of 1.5 J is lower than that of a single 3.0 J impact.