Numerical investigation of the low-velocity impact damage resistance and tolerance of composite laminates with preloads

Composite materials employed in engineering services are often subjected to preloads such as pre-tension and pre-compression, necessitating a comprehensive understanding of their effects on the Low Velocity Impact (LVI) damage resistance and tolerance. Driven by this, a Finite Element Analysis (FEA) model, accounting for fibre damage, matrix damage, and delamination, has been developed to capture the LVI behaviors of composite laminates subjected to various preloads. Furthermore, the developed model has also been employed to predict the Compression After Impact (CAI) strength of these composite laminates which have been impacted under pre-loading conditions. By comparing the modelling results with experimental data, the fidelity of the model is demonstrated, especially revealing a deviation of less than 10 % between the measured and predicted CAI strengths. The validated model is then employed to further explore the relationships between LVI behaviors, CAI strength, and different types and magnitudes of preloads under varying impact energies. The findings indicate that a monotonic transition in preloading from compression to tension leads to a reduction in LVI delamination area and energy dissipation, while for CAI strength, it is related with the stacking sequence.