Comparison of Compression-After-Impact and Flexure-After-Impact protocols for 2D and 3D woven fiber-reinforced composites

Post-impact mechanical response of 2D and 3D woven glass/epoxy composite plates and beams of equivalent areal density are evaluated using both Compression-After-Impact (CAI) and Flexure-After-Impact (FAI) testing protocols. Residual strength and stiffness for CAI and FAI are compared after normalization of impact energy with respect to specimen volume. Post-impact flexural strength and modulus from FAI testing exhibit larger reductions with respect to impact energy in comparison to CAI results. At the largest impact energies tested, FAI testing yields 70% reduction in flexural strength compared to only 20% reduction (in compressive strength). Architecturally, 3D woven composites retain greater post-impact mechanical performance as a result of the through-thickness Z-tow which suppresses delamination growth and opening during impact.