THE REDUCTION OF ENVIRONMENTAL-EFFECTS ON TENSION-TWIST COUPLED COMPOSITE TUBES

A method is presented for designing composite laminates which will pro duce tension-twist coupling in tubes but show reduced variation in tha t coupling due to hygrothermal effects. Experimental results are prese nted which demonstrate coupling variations due to changes in temperatu re and moisture content. These effects are modeled theoretically as th e variation of constituent shear moduli since shear modulus dominates coupling behavior. This model predicts the same form of variation as s een in the experimental measurements of coupling. Based on laminates w hich do not exhibit thermally induced shear deformation, hybrid lamina tes were developed that can reduce or eliminate hygrothermal sensitivi ty while retaining coupling.