Maximal errors due to use of equivalent properties for sublaminates

Sublaminates are often used in design optimization to reduce the complexity of the design task, to simplify modeling, to reduce data input to analytic al models, and to provide confidence in failure prediction. Sublaminates se lected for design often use fixed ratios of ply orientations that have been previously tested and are well characterized. Because ratios of the ply or ientations are fixed, designers approximate the properties of sublaminates using equivalent orthotropic properties. The maximal errors in bending stif fness and buckling loads due to use of equivalent properties are investigat ed. It is found that repeating half of the sublaminate on either side of th e symmetry plane results in larger errors than repeating the entire sublami nate. For the former ease, errors of up to about 20% are found even with fo ur sublaminate repetitions, whereas for the latter case, errors were under 6%, Predicted buckling loads exhibit the largest errors when equivalent pro perties are used for plates with large aspect and load ratios.