Delamination failure investigation for out-of-plane loading in laminates

In contrast to failure approaches at the lamina level or the micromechanics level, the present work concerns failure characterization at the laminate level. Specifically, attention is given to the ultimate failure characterization for quasi-isotropic laminates. This is in further contrast to the commonly used approaches for initial damage or progressive damage. It is shown that the analytical failure forms decompose into two modes, one for out-of-plane, delamination-type failure and one for in-plane, fiber-controlled-type failure. The work here is mainly given over to the delamination mode of failure. Experimental results are presented for laminates in this mode of failure. These results are then integrated with the analytical forms to give a simple criterion for delamination failure.