OPTIMAL THROUGH-THICKNESS TEMPERATURE-GRADIENTS FOR CONTROL OF INTERLAMINAR STRESSES IN COMPOSITES

Analytical solutions are sought for optimal temperature distributions to control the interlaminar stresses near the free edges of composite laminates subjected to uniaxial loading. Optimal through-thickness tem perature gradients are obtained by minimizing appropriate performance indices that are functions of the far-field properties, with respect t o the through-thickness temperature differences. Through the applicati on of these temperatures, effects of local mismatches as well as globa l mismatches in two of the elastic properties, the Poisson's ratio and coefficient of mutual influence, are minimized. Numerical examples ar e given for several lay-ups made of graphite epoxy. It is shown that f or a cross- or angle-ply laminate a uniform temperature rise or drop c an completely eliminate all of the interlaminar stresses, whereas for other Laminates nonuniform temperature distributions must be applied t o minimize the stresses.