Damage Prediction in Fiber Reinforced Composites

Various failure modes can occur in a composite laminate subjected to external load. With the increasing external load, the failure evolves in composite laminate and evolution behavior depends on the failure modes. Thus, the knowledge of the damage mechanisms in composite laminate plays an important role in the practical design of composite structures. The stiffness degradation phenomenon of fiber reinforced composite laminates under external loads is an important response to the damage and failure evolution of composite laminates. The analysis of stiffness degradation of composite laminates under external load is called as the progressive failure analysis. In this work, a 3D finite element based progressive damage model is developed for fiber reinforced composite laminates and it is applied to CFRP laminates having multiple holes and also to multi-pin joints in CFRP laminates. The developed model is suitable for predicting failure and post failure behavior of the laminates. The PDM involves stress analysis, failure analysis and damage propagation. Digital image correlation experiment is carried out to perform whole field surface strain analysis of the composite laminates. Finite element model is validated by comparison of whole field surface strain and displacement from finite element prediction with digital image correlation results. The failure modes predicted by PDM is found to be in good agreement with experimental observation. Also load-deflection behavior predicted by both PDM simulation and experiment are found to be in good agreement thereby confirming the accuracy of PDM implementation. Effect of spacing between the holes on the maximum stress value in the panels is also further investigated