Paper number 1356

PREDICTION AND EVALUATION OF LOCAL AND GLOBAL OPTIMA IN STRENGTH DESIGN OF COMPOSITE LAMINATES

Philippe M. Manne and Torben K. Henriksen

European Space Agency / European Space Research and Technology Centre
Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
manne @alumni. stanford. org
thenriks@estec.esa.nl

Summary

A thicker composite laminate is not necessarily safer than a thinner one of the same relative proportions. Although subjected to the same loadcase, it may even fail. Therefore, the paths followed by strains in laminates upon proportional scaling of their thickness are investigated so as to determine upfront the number and range of safe design thickness allowables. It is shown that one or two such intervals may exist. Their existence and boundaries are predicted by decomposing nominal strains into N-strains and M-strains, i.e. the strain fractions due to in-plane (N) and bending (M) loads respectively. Incidently, this analytical prediction method enables identification and localization of local and global strength optima- An example reveals the inherent consequences on manufacturing tolerances and design safety margins.

Keywords

optimization, strength, scaling, local/global, mechanical properties.