The experimental assessment of the various surface modifications on the tensile and fatigue behaviors of laminated aluminum/aramid fibers-epoxy composites

Abstract Fiber metal laminates (FMLs) are introduced as the kind of advanced hybrid composites consisting of the metals and composite layers, which the adhesion between those has an important role on the static and dynamic mechanical properties of these structures. To do so, the mechanical abrading, alkaline etching, forest products laboratory (FPL) and anodizing surface modification methods were performed on the 2024 aluminum for fabricating aramid fiber-reinforced aluminum laminate (ARALL). After that, by using tensile and fatigue tests as well as micro/macro-structural investigations, the static and dynamic mechanical properties of ARALL structures were studied. Based on the fatigue results at the stress level of 90%, the mechanical surface modification caused that the fatigue cycles reached to 2155 cycles, which was the highest fatigue cycles. Whereas in the stress level of 45%, the anodizing surface modification with the 34,420 fatigue cycles had the highest improvement. Given up the tensile results, the FPL and anodizing surface modified FMLs had the highest tensile strength, which were 317 and 319 MPa, respectively. The microstructural investigations showed that by using the various surface modification methods, the absorbing energy mechanisms of fatigue loadings by aramid fibers changed. Also, changes in the number and diameter of formed dimples in the aluminum skins were seen.