Three-Dimensional Curing Stresses in Symmetric Cross-Ply Laminates with Temperature-Dependent Properties

Abstract

A fully three-dimensional finite element analysis of curing stresses in cross-ply boron/epoxy composite laminates is presented. Comparisons are made between constant and temperature- dependent material properties and a constitutive model which includes the coupling between stress and temperature dependence of material properties. Also examined is the error introduced by the common assumption of equality of all shear moduli (G12, G13, G23) and certain Poisson's ratios (ν 12, ν13, ν23). Interlaminar stresses near the laminate midplane and 0/90 interface are presented, including effects which occur near the free corner of the laminate. Differences in the three thermal expansion models are found to be significant for the boron/epoxy system in some stress terms and negligible in others. The errors introduced by the coefficient equality assump tions are found to be small. Omission of the stress-thermal expansion interaction term is found to result in substantial underestimates of curing stresses. This is in agreement with the results of previous investigators which included the coupling term in a lamination theory model.