Investigation of composite filled hole coupons and lockbolt fastened joints under impact loading

Two different composite fastened configurations, i.e., the filled hole and the single-lap double-fastener joint, subjected to impact tensile loads, are investigated using efficient modelling techniques. The novel simulation methodology of the ‘stacked shell’ approach (or ‘2.5D’ approach) is exploited, in order to model the fastened composite coupons using the nonlinear explicit dynamics finite element code LS-DYNA. In the stacked shell approach, the composite plates are represented by discrete sublaminates of shell elements, which are tied together using interface elements with cohesive zone properties, resulting in a computationally efficient methodology of solving problems that involve significant inter-ply and intra-ply material failure. The numerical models are validated against relative experimental test data, derived from experiments which are performed within the investigated impact loading regime. The simulation results demonstrate that the models are capable to predict the onset of the damage, the failure modes and the load–displacement response of the fastened specimens with notable accuracy. In addition, the numerical investigation has shown limited loading rate sensitivity in terms of strength values for both of the examined configurations, while the lap joint samples illustrate pronounced changes in the final failure mode as the loading rate increases.