A study of interlaminar stresses in variable stiffness plates

Variable stiffness composite panels have been in continuous development for the last two decades. Several studies have been carried out to evaluate their structural response under different hypotheses. It is known that correct prediction of the onset of delamination in multilayer composite laminates requires an accurate evaluation of interlaminar stresses. Although finite element codes provide results for interlaminar stresses, they are not continuous both across and along layer interfaces due to the use of C-o interpolated elements. In this work, a methodology for obtaining interlaminar stresses is extended and applied to the case of variable stiffness composite panels. Pagano's three layer reference case is investigated for both constant stiffness and variable stiffness cases. A set of analyses are carried out to demonstrate the performance of the method and the variation in the stress response of the panel due to changes in composite layup. Results show that the distribution of shear stresses in the panel presents an significant variation depending on the stacking sequence. A debonding failure criteria is used to evaluate the performance of different variable stiffness configurations, obtaining improvements compared with constant stiffness panels. (C) 2011 Elsevier Ltd. All rights reserved.