Senior engineer Grumman Aircraft Systems Division, Grumman Corporation, Bethpage, NY
Pages: 11 Published: Jan 1988
A closed-form approximate solution for the total strain energy release rate (G) of an elliptically shaped delamination has been developed from thin-film assumptions that treat the delamination as a clamped plate subject to enforced boundary displacements. Approximate equations are derived which couple the large deflection membrane stresses to the out-of-plane deflections. The model restricts the boundary to remain elliptical as the delamination grows. By applying the simple failure criterion that rapid growth of the delamination (which occurs when G reaches a critical value) precipitates the final failure of the laminate, the predicted failure stresses can be correlated with post-impact strength data available in the literature. The Mode I critical G is required for a good correlation, although the model calculates the total G averaged around the perimeter. For impact damage, data on delamination depth are rarely available. However, it was found that by assuming a delamination interface that results in the lowest failure strain, correlation with test data was obtained.
composite materials, impact, delamination, defects, buckling, fracture mechanics, laminates
Paper ID: STP26134S