A Thesis presented to the Faculty of San Diego State University.

In tapered closeouts designs, the sandwich laminate is transitioned to a solid laminate, with high compressive strength, by eliminating the core. Tapered closeouts are found to be prone to fatigue failure by delamination. The delaminations initiate at the region where the upper and lower facesheet meet to form a solid laminate, due to the presence of voids or resin rich areas. These cracks then grow along the facesheet-core interfaces and lead to fatigue failure by delamination. Improving the fatigue life of sandwich closeouts requires a better understanding of the stresses and the damage growth mechanisms.

The goal of the study is to elucidate the deformation mechanisms, load transfer, and interface stresses in the tapered close out section of a sandwich.