Hypervelocity impact behavior and residual flexural strength of C/C composites

- Defects in the upper side are associated with impact pressure of the projectiles.
- The upper side of post-impacted sample presents a compression failure mode.
- Defects in the bottom side are dominated by delamination and transverse cracks.
- Delamination occurs between mat plies and other plies (0° and 90° cloth plies).
- The strength decreases of post-impacted sample-R were bigger than that of sample-F.

This paper describes the hypervelocity impact behavior and the residual strength of carbon fiber reinforced carbon (C/C) composites under different impact velocity. Impact tests of 2.5D C/C composite samples have been performed using one stainless steel ball driven by solid explosive to detect correlations between the impact direction and damage distribution and the residual flexural strength of the composites. Results showed that the impact resistance of the C/C composites was affected by the impact velocity. Damage modes evolved from matrix cracking and fiber breakages to spallation and delamination along the impact direction. Furthermore, delamination occurs delamination occurred in mat plies and 90° plies, resulting from poor load-bearing capability of short mat layers and weak adhesion between fiber bundles. In addition, the residual strength of the damaged C/C composites decreased by 30.6-43.5% and 47.4-48.6% in the upper side and bottom side, respectively. The flexural stress-strain curves and fracture modes of post-impacted composites were various due to the diverse damage types in different areas.