INFLUENCE OF CURING STRESSES ON EXTENSION-TWIST COUPLING IN LAMINATEDCOMPOSITE STRIPS

An analytical model developed previously for the finite displacement o f laminated composite strips exhibiting extension-twist coupling is ex tended to include the influence of hygrothermal stresses. A closed-for m expression for the twist associated with the curing stresses is deri ved. The relationship between applied extension and twist is obtained in closed form as well, and the contribution of the curing stresses is isolated. A set of angle-pig laminated composite strips made of a gra phite/cyanate material system is manufactured and tasted. A custom-mad e air bearing apparatus is used in the testing to allow one end of the strip to twist as axial load is applied. Test results depict the nonl inear axial force-twist behavior and the analytical predictions are in close agreement with test data and a geometrically nonlinear finite e lement simulation.