Experimentally Validated Progressive Failure Modeling of Composite Pi Joints

A computational model has been developed to analyze composite pi joints subjected to pulloff and side-bend loading. A discrete damage modeling approach is used to capture the interactions between intralaminar damage (matrix cracking) and interlaminar damage (delamination). Cohesive element interlayers and matrix-crack elements are governed by the same mixed-mode traction-separation formulation, resulting in a unified damage framework. The finite element model was calibrated using experimental data from pristine and defective joints. In the calibration process, in situ cohesive material properties were backcalculated from pulloff tests such that the accurate prediction of structural response and the damage evolution of pi joints were possible. Computational predictions for both pulloff and side-bend loading are shown to agree well with experimental results for joints subjected to pulloff and side-bend loading.