Transverse impact characteristics of adhesively bonded composite single lap joint

Impact force and deformation behavior of adhesively bonded single lap composite joints for transverse impact are studied through a pilot project and validated using Finite Element Analysis (FEA). At present there is no standard which provides guidelines in testing adhesively bonded joints or structures at coupon level. An attempt is made here to formulate the testing procedure through an experiment. Adhesively bonded glass-epoxy lap joints are transversely impacted using three different hemispherical impactors at three different energy levels. The effect of impactor diameter on impact force, target deformation and energy absorption are of particular interest. An explicit non-linear contact analysis using LS-Dyna-3D is carried out. FEA results are observed to be in close agreement with the experimental results. The results show that for a same impact energy level larger impactor generates more force whereas smallest diameter produces highest deformation and most through thickness damage. The same finite element model is used to investigate the effect of lay-up schedules and number of plies on impact force and deformation in composite lap joint. The study of various lay-up schedules reveals that fibers in [0/90] direction have better control on target deformation than fibers in [45/-45] direction for the given boundary condition in transverse impact. Also as the numbers of plies are increased the system becomes stiffer resulting in high impact force. The target deformation is observed to become more localized with increase in laminate thickness.