Maximal Errors due to Use of Equivalent Properties for Sublaminates

Abstract

Sublaminates are often used in design optimization to reduce the complexity of the design task, to simplify modeling, to reduce data input to analytical models, and to provide confidence in failure prediction. Sublaminates selected for design often use fixed ratios of ply orientations that have been previously tested and are well characterized. Because ratios of the ply orientations are fixed, designers approximate the properties of sublaminates using equivalent orthotropic properties. The maximal errors in bending stiffness and buckling loads due to use of equivalent properties are investigated. It is found that repeating half of the sublaminate on either side of the symmetry plane results in larger errors than repeating the entire sublaminate. For the former case, errors of up to about 20% are found even with four sublaminate repetitions, whereas for the latter case, errors were under 6%. Predicted buckling loads exhibit the largest errors when equivalent properties are used for plates with large aspect and load ratios.