Comparative analysis of modelling techniques for impact on thick fabric composite structures

Abstract

Despite the increased use of thick fabric Carbon Fibre Reinforced Polymer (CFRP) materials in highly loaded aerospace structures (e.g., 20-50mm thick CFRP structures), a comprehensive characterisation of damage due to impact events on these structures remains an elusive and challenging task. To address this issue, three methods with varying degrees of computational complexity are developed to simulate and predict a representative impact problem on a thick composite plate. These simulation methods range from a low-fidelity 1D semi-analytical impact response model to high-fidelity 2D and 3D numerical impact damage models. The accuracy, in terms of impact response and damage prediction, is assessed by comparison with experimental results. It was found that the higher fidelity does not directly translate to a higher accuracy due to challenging modelling strategies for the 2D and 3D numerical impact damage models. The 1D semi-analytical impact response model was found to be the most accurate in predicting the force and displacement histories of both large-mass and small-mass impact events. However, this model is not capable of predicting the extent of damage. Comparison of the resulting impact damage from the 2D and 3D numerical impact damage models with experiments showed that improvements are required to capture the correct damage mechanisms. These damage mechanisms are complex and increasing the model complexity requires an extensive evaluation of the modelling strategies and numerical variables. Improvements are suggested that should increase the accuracy of these models. Dynamics are important for thick laminates as there is almost no plate bending and most of the impact energy is absorbed in local damage and deformations. Thinner composites generally experience more bending and can therefore be evaluated quasi-statically.