Impact-under-load damage tolerance of a fibre metal laminate

Abstract

The effect of in-plane loading on the low energy impact damage tolerance of a fibre metal laminate (FML) is experimentally investigated. The FML consisted of stacked layers of aluminium alloy (AA2024-T3) and S2-glass/epoxy (GFRP) composite. The FML was impacted in the transverse direction at increasing energy levels (up to ∼ 20 J) while preloaded in tension or compression at different levels of elastic strain (up to 8000 με). The amount of impact-induced damage and the post-impact compressive strength of the FML were both dependent on the type and magnitude of the preload. The FML sustained plasticity damage and cracking to the aluminium layers; fibre damage, matrix cracking and delamination cracking within the GFRP layer; and debonding cracking between the metal and composite layers under impact loading. The amount of impact damage to the FML increased with the tension and compression strain levels, with more damage created under the tension preload condition. The post-impact compressive strength of the FML also decreased with increasing preload strain, with the reduction being greater for tension compared to compression. The research provides new insights into the impact damage tolerance of FMLs used as load-bearing structural materials.