Survivability of Affordable Aircraft Composite Structures. Volume 2: High Strain Rate Characterization of Affordable Woven Carbon/Epoxy Composites

Abstract : Studies on the high strain rate impact tests performed on conventional unidirectional and affordable woven carbon/epoxy composites using the Split Hopkinson's Pressure Bar (SHPB) setup are presented in the this report. Stitched and unstitched samples made of plain and satin weave carbon/epoxy composites were subjected to high strain rate compression loading at strain rates varying from 320/s to 1149/s using a modified SHPB setup. Further unstitched samples were subjected to inplane off-axes loading at high strain rates at various angles. Failure modes were characterized through optical and scanning electron microscopy. Results of the test indicated that the peak stress increased with increase in strain rate. Under off-axes loading, the peak stress decreased with increase in off-axes angle. Stitching helped in preventing splitting damage. Studies on carbon/epoxy plates using penetrating SHPB indicate that the strain rate, ultimate strain, and energy released increased nonlinearly, particle velocity and displacement increased linearly with impact energy and the dynamic modules seems to decrease nonlinearly with impact velocity, energy released, strain rate and strain. Penetration limit (PL) increased with increase in the thickness of the laminate. Damage modes include perforation and plugging above PL.