The Reduction of Environmental Effects on Tension-Twist Coupled Composite Tubes

Abstract

A method is presented for designing composite laminates which will pro duce tension-twist coupling in tubes but show reduced variation in that coupling due to hygrothermal effects. Experimental results are presented which demonstrate coupling vari ations due to changes in temperature and moisture content. These effects are modeled the oretically as the variation of constituent shear moduli since shear modulus dominates cou pling behavior. This model predicts the same form of variation as seen in the experimental measurements of coupling. Based on laminates which do not exhibit thermally induced shear deformation, hybrid laminates were developed that can reduce or eliminate hygro thermal sensitivity while retaining coupling.