An Efficient Analysis for the Debonding of Stitched Skin-Stiffened Structures

An analysis based on plate finite elements, nonlinear spring elements and the virtual crack closure technique has been implemented to study the effect of stitching on strain energy release rates for debond configurations. The stitches were modeled as discrete nonlinear spring elements with a compliance determined by experiment. The axial and shear behavior of the stitches was considered, however, the two compliances and failure loads were assumed to be independent. Both a double cantilever beam (mode I) and a mixed mode skin-stiffener debond configuration were studied. In the double cantilever beam configuration, G I began to decrease once the debond had grown beyond the first row of stitches and was reduced to zero for long debonds. In the mixed-mode skin-stiffener configuration, G I showed a similar behavior as in the double cantilever beam configurations; however, G II remained nonzero over the range of debond lengths considered.