MODELLING DAMAGE IN COMPOSITES SUBJECTED TO IMPACT AND COMPRESSION AFTER IMPACT

Abstract

Composites are prone to impact damage, which can reduce the compressive residual strength significantly. Therefore, it is essential to design composite structures for damage tolerance. It is important to better understand failure mechanisms to develop more efficient design strategies. Advanced progressive damage modelling of composites can help us achieve these objectives. In this work, high-fidelity finite element (FE) models are developed for integrated analysis of impact damage, subsequent growth during compression and prediction of residual strength. Firstly, a Continuum Damage Mechanics (CDM) based model is employed to obtain damage through an impact analysis. Secondly, the model with embedded damage from impact is subjected to Compression After Impact (CAI). The relationship between failure mechanism and CAI strength is established for a range of quasi-isotropic laminates. The underlying mechanism leading to improved damage resistance in hierarchical bio-inspired composite is then investigated. To model the delamination/matrix interaction in bio-inspired composite, a discrete crack model is developed for impact and CAI. Two improvements over existing discrete crack modelling strategies are proposed. In helicoidal composites, the existence of a spiralling (staircase) damage results in reduced through-thickness delamination. This allows the helicoidal layup to retain more compressive strength (18 percent) in comparison to quasi-isotropic laminates.