Experimental and finite element analysis of curved composite structures with C-section

The curved region in composite structures is vulnerable and easily experiences delamination under opening load due to the localized transverse stresses. This failure occurred in a composite primary part, e.g. spars and bulkheads, of an aircraft can intensively reduce its rigidity and strength. In this study, various moderately thick composite laminates with a C-section, which were cut from a carbon-epoxy C-spar, were tested with an opening load for different thicknesses and heights. On the basis of the test results, a three-dimensional finite element model in conjunction with Ye-delamination failure criteria was proposed to investigate the failure behavior as well as to predict the failure load of the structures. The finite element models were verified using strain results at specific locations. Failure loads were predicted using the damage zone method (DZM). Damage volume and damage volume ratio were used to evaluate damage zone in the model. Analysis results show deviations of less than 0.7-9.0% of the experimental results in the case of using damage volume ratio. The proposed damage zone method was also examined for laminated beams with different corner radius and good agreement was obtained.