Evaluation of Progressive Failure of Composite T-Joint Using Mixed Mode Cohesive Zone Model

Abstract

T shaped stiffeners are the most commonly used structures in aerospace components. De-lamination/de-bond initiation followed by its growth is one of the most common reasons for failure in a fiber reinforced composite structure. It is caused by the interlaminar normal and shear stresses between different structural constituents. In a typical structural T-joint, the failure mechanism and location may differ based on the structural design parameters like fillet radius, thickness, layup sequence, filler stiffness, etc. In this study, finite element analysis has been performed using cohesive zone model (CZM) on a composite T-joint to simulate the pull out test conditions. A simplified plane strain model coupled with CZM is proposed, which can evaluate the failure initiation and progression accurately with lesser computational efforts. The final failure occurs at a displacement of 8.04 mm and the computed failure load is 2240 N. The results obtained by the proposed numerical model are validated by experimental results and it is observed that predicted regions of failure, failure displacements and failure load calculated are correlating reasonably well with the experiment.