Influence of neighbouring damage on delamination growth in multiple indented composites

To improve current design approaches for composite structures, it is required to further investigate the damage interaction effects of composite materials under multiple out-of-plane concentrated loads. It is first necessary to comprehend the dependence of the effective delamination threshold, which describes whether a delamination grows on pre-existing delamination damage in composite laminates. A com-bined experimental and numerical study is presented, in which two sequential out-of-plane quasi -static indentations are applied to fully clamped composite laminated panels, with changing distances between the two indentation locations changing. The results show that the second indentation delami-nation is more likely to propagate, particularly in the straight-line direction from the second indentation site to the first one, which can be interpreted as a decrease in the effective delamination threshold asso-ciated with microcracks ahead of the delamination front. The relevant percentage reduction is 37% and is independent of the imposed indentation load. As a crucial take-away, designers should be mindful that the damage interaction effects could result in greater damage than the sum of the individual cases.& COPY; 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).