Effect of Interlaminar Stresses on Crush Behavior of Composite Structures

The study has been conducted to analyze the effect of interlaminar stresses on the crush behavior of laminated composite structures. Several sets of test data of columns under axial crush load were analyzed. Modes of collapse were identified. Interlaminar stresses due to in-plane axial crush load were calculated and compared with interlaminar strengths. The analysis showed that when laminates have no significant cracks or voids, the interlaminar stresses have no effect on crush mode up to the maximum load, and a thin-walled composite column fails in local buckling mode. When the laminates have initial imperfections, cracks or voids create interlaminar stress concentration and cause the delamination failure. In this case the column walls are split through the thickness into two portions, one crushed inward and the other crushed outward. The study also indicated that fiber orientation is important in initiating interlaminar stresses.