Normal and oblique hypervelocity impacts on carbon fibre/peek composites

A series of normal and oblique hypervelocity impact tests were performed on carbon fibre/PEEK composite specimens using the Light Gas Gun facilities at the University of Kent at Canterbury. The tests were conducted on 16 ply and 24 ply targets, using 1 mm and 2 mm aluminum projectiles, at velocities of approximately 5 km/s, and at impact angles of 0, 30 and 45 degrees. The primary objective of this investigation was to add oblique impact data to the University of Toronto Institute for Aerospace Studies (UTIAS) database on hypervelocity impact damage to composites. The parameters investigated in this study were debris cloud (primary and secondary) dispersion cone angles, (equivalent) entry and exit crater diameters, and front and rear surface delamination damage zones. The results of the analysis showed that the cone angles were not symmetric about the projectile velocity vector, maxima for both angles occurring at a normalized energy of approximately 55 J, followed by an asymptotic decrease. The results obtained for the entry crater diameter and equivalent entry damage diameter were found to be in good agreement with the existing UTIAS database. For a given impact energy, the damage area in the 24 ply targets was found to be nearly twice that of the damage in the 16 ply targets. Results were found to be in good agreement when compared, using an empirical equation, to predictions of impact damage of Al projectiles on aluminum targets (when a scaling factor of 0.9 was applied to the PEEK data to account for the greater damage in composites).