Three-Dimensional Analysis of a Postbuckled Embedded Delamination

Delamination growth caused by local buckling of a delaminated group of plies was investigated. Delamination growth was assumed to be governed by the strain- energy release rates G _I , G _II , and G _III . The strain-energy release rates were calculated using a geometrically nonlinear, three-dimensional, finite element analysis. The program is described and several checks of the analysis are discussed. Based on a limited para metric study, the following conclusions were reached: 1. The problem is definitely mixed-mode. In some cases G _I is larger than G _II ; for other cases the opposite is true. 2. In general, there is a large gradient in the strain-energy release rates along the delamination front. 3. The locations of maximum G _I , and G _II depend on the delamination shape and the ap plied strain. 4. The mode III component was negligible for all cases considered. 5. The analysis predicted that parts of the delamination would overlap. The results pre sented herein did not impose contact constraints to prevent overlapping. Further work is needed to determine the effects of allowing the overlapping.