The influence of preload and boundary conditions on pre-damaged composite plates subject to soft-body impact

Highlights: • We investigate the influence of soft-body impacts onto pre-damaged CFRP plates. • Material delamination is simulated using a bilinear cohesive element failure model. • Simulation results are validated with comparison to theory and test data. • Tensile preload and plate compliance reduce the extent of impact damage. - Abstract: This research investigates the influence of preload and boundary condition compliance on low-velocity impact damaged CFRP T800S/3900-2B plates subject to secondary higher-velocity soft-body impact (50 J, 75 J, 100 J). A bilinear cohesive element based delamination model combined with ply-based composite material failure was developed using LS-DYNA 971. Double Cantilever Beam (DCB), 3-point End-Notched Flexure (ENF), and Fixed Ratio Mixed Mode Bending (FRMMB) simulations validate the accuracy of the delamination model when compared with theory. The low-velocity impact simulations were shown to compare well with the results of drop-tower impact experiments and ultrasonic inspection data in terms of maximum impact force and projected delamination area. An investigation of boundary condition compliance in the direction of impact showed a reduction in peak impact force, interlaminar delamination and intralaminar failure with increasing coupon translation. High-velocity impact simulations based on the model with initial damage showed a reduction in interlaminar delamination damage with tensile preload when compared to compressive preload and unloaded cases for all impact energies.