A comprehensive study of the flexural behaviour and damage evolution of composite laminates using a progressive failure model

Composite laminates are widely used in various engineering applications due to their excellent mechanical properties and lightweight nature. However, predicting their behaviour and damage evolution remains a challenge due to the complexity of the inter/intralaminar failure modes. In this paper, we propose a new progressive damage model that takes into account both inter and intralaminar failure modes to accurately predict the flexural behaviour and damage evolution of composite laminates under three-point bending. The proposed model incorporates a progressive failure algorithm and gradual stiffness degradation rules through a user defined subroutine UMAT to predict further damage evolution following damage initiation, estimated by the combination of the three-dimensional Puck failure criteria and the cohesive zone model. One of the objectives of this research is to develop a finite element model (FEM) capable of simulating the behaviour of different composite laminates under three-point bending, to reduce effectively processing time and testing costs. As part of the investigations carried out in this study of two types of composite laminates IMS194/CYCOM977-2 and AS4/PEEK, we considered the prediction of ultimate load and stiffness. The results showed significant agreement with the experiments, as well as degradation trends in the load vs. deflection curves. In addition, the interaction between matrix cracking and delamination has been addressed, alongside the impact of cohesive zone elements on the strength of the material. Corrodingly, we found that the interface strength should be considered, to fully exploit the laminate features, and to reduce the effect of delamination which causes intra-laminar longitudinal cracks to appear under the effect of higher inter-laminar stresses. Furthermore, a mesh dependency of the model used has been conducted, to determine the optimal mesh size and shape required to accurately capture the behaviour of the composite laminates. The significance of our study lies in the development of a more accurate and reliable progressive damage model that can improve the design and engineering of composite laminate.