Parametric study of the behavior of graphite/epoxy panels with stiffener terminations

The results of a parametric study examining six types of stiffener terminations for stiffened graphite/epoxy panels are presented. Stiffener blades are terminated by attaching to another blade, by tapering the stiffener height, by tapering the stiffener thickness, or by a combination of these methods. Stiffener flanges are also terminated abruptly or by tapering their thickness. Flange length is also varied. Both thin-skin panels and thick-skin panels art? considered. Panels were analyzed with a nonlinear finite element analysis code to determine panel response and failure modes. Midplane axial and shear strains, surface strains, interlaminar strains, and failure predictions for the panels are discussed, These results indicate that the mechanism initiating failure is dependent on the stringer configuration of the panel. Interlaminar stresses and bending must be considered to predict the failure of thin-skin panels, and interlaminar stress, in-plane shear strains, and axial strains must be considered to predict the failure of thick-skin panels.