A damage index proposal for shear-after-impact of laminated composite plates

This work presents a damage index proposal based on an experimental approach to evaluate the behavior of laminated fiber-reinforced composite plates under in-plane shear-after-impact conditions. Therefore, drop-weight experimental tests for low-energy impact (face-on in the barely visible impact damage range) are performed in laminates, as well as in-plane shear tests are carried out by 3-rail device to obtain stress–strain curves for pristine and impact-damaged composite plates. A new coupon based on the ASTM standards is designed to fit impact and in-plane shear experimental devices. The phenomenological damage index for shear-after-impact is energy-based being able to quantify the damage severity in the composite plates as shown by experimental results. Simple guidelines for its determination are also summarized. Furthermore, computational simulations via ABAQUS with a User Material (UMAT) subroutine accounting for progressive damage analysis are performed to predict damage index values for different degradation scenarios. Finally, it is discussed and concluded that the proposed damage index and the experimental approach can be combined with the already consolidated procedures, such as flexure- and compression-after-impact, to evaluate with more accuracy the residual strength of impacted laminates of fiber-reinforced composite materials.