Failure of Stitched Composite L-Joints Under Tensile Loading - Experiment and Simulation

This article presents an experimental and numerical investigation into the influence of transverse stitching on failure of composite L-joints under tensile loading. Six unstitched and six stitched L-joint specimens were manufactured and tested under quasi static tensile loading. It was observed that the average measured failure load and the associated crosshead displacement for the stitched L-joint specimens are increased significantly compared to those for the unstitched specimens. Full 3D and 2D plane strain finite element (FE) models were developed to simulate both stitched and unstitched L-joints with an implemented stitch element. The load-displacement curves and results predicted via FE models compare favorably with the experimental results. For the stitched L-joints, it is shown that the observed delamination in the elbow region of the flange can be modeled by using a softening model for epoxy layer.