Stacking Sequence and Geometrical Effects on Low-Velocity Impact Behaviors of GLARE 5 (3/2) Fiber-Metal Laminates

Impact responses and damage induced by a drop-weight on GLARE 5 (3/2) fiber-metal laminates (FMLs) with various lay-up configurations were studied experimentally. The effect of specimen geometry was also considered. The damage characteristics were evaluated using both nondestructive ultrasonic and mechanical-sectioning techniques. Only the contour of the entire damage area could be obtained using ultrasonic C-scan, whereas more details of the damage were provided through the mechanical-sectioning technique. The impact properties of FMLs were affected by laminate stacking sequence. The first severe failure induced by low-velocity impact occurred as debonding between aluminum and the adjacent fiber-epoxy layer at the nonimpact side. It was followed by a visible crack in the outer aluminum layer at the nonimpact face. GLARE 5 made of unidirectional fibers had the least impact resistance; followed by cross-ply and angle-ply configurations; while the quasi-isotropic lay-up showed the best in resistance to impact. By introducing circular, rather than square, geometry as the outer perimeter of the specimens, the damage patterns as well as impact behaviors changed due to the relative anisotropy of the specimen with respect to the specimen clamping.