Axisymmetric stiffened composite panels with a stress concentrator under in-plane compression

The in-plane compressive strength of thin-skinned stiffened composite panel with stress concentrator is examined. Two possible in-plane failure mechanism are investigated. First one is the near the surface instability on the edge of the cut-out, where high stress gradients are expected due to the stress concentration and the heterogeneity throughout the thickness of the laminated skin. The 3D analytical formulae allowing simple parametrical investigation of the phenomenon considered are derived. Another failure mechanism is fiber microbuckling in the 0° plies. The equivalent crack model is used to predict the compressive strength of multidirectional composite laminate. Influence of stiffener onto compressive strength of thin-skinned panel with a hole is clarified for both mechanisms. Good agreement between experimental results and predicted values for critical load is obtained.