Fatigue of fiber-metal-laminates with aluminum core, CFRP face sheets and elastomer interlayers (FMEL)

Fiber-Metal-Laminates (FML) with high strength carbon fiber reinforced epoxy face sheets, aluminum 2024-T3 core layer and elastomer interlayers were experimentally examined under tension-tension fatigue loading to describe the material's behavior under near-application loads. Symmetric laminates with CFRP face layers were tested in fatigue experiments according to ISO 13003. The failure definition was stiffness degradation of 20%. A lifetime prediction was carried out by superposition of the constituents predictions. The CFRP lifetime was calculated according to Ogin et al. and the aluminum sheet was predicted according to Coffin-Manson. Damage evolution was investigated using ex-situ X-ray CT-scans and thermal analysis. A S-N curve was deduced from the experiments and validated the lifetime prediction. The damage in the laminate was correlated to the stiffness evolution throughout the fatigue experiments.