Low-Velocity Impact Study on GLARE FMLs Using Various Indenters

Impact responses and damage induced by drop-weight impact on two types of glass-laminated aluminum-reinforced epoxy (GLARE) fiber-metal laminates (FMLs) were studied experimentally and numerically. Indenters with various shapes and sizes were used under different impact energies. For line-nose Charpy indenters, the effect of the angle between the indenter and the fiber direction was also investigated. Both the nondestructive ultrasonic and mechanical sectioning techniques were adopted to evaluate impact damage in the laminates. The results showed that GLARE 3 (cross-ply) offers higher impact resistance than GLARE 2 (unidirectional). The first failure at low-velocity impact occurred as delamination between the nonimpacted-side aluminum and the adjacent fiber-epoxy layer, then was followed by a visible crack in the outer aluminum layer at the nonimpacted side. More severe local damages appeared with smaller indenters, indicating that the energy dissipated mainly through delamination and cracks for smaller-size indenters. On the other hand, larger global deflection occurred if larger-size indenters were used, implying more energy might have been absorbed owing to extensive global deformation of the FMLs. Finite-element simulations were carried out using an explicit finite-element program. The damage patterns, histories of impact force, energy, and deflection, as well as the dynamic contact stiffness, were obtained numerically. Good agreement was obtained between experimental results and finite-element simulations.