Influence of Curing Stresses on Extension-Twist Coupling in Laminated Composite Strips
An analytical model developed previously for the finite displacement of laminated composite strips exhibiting extension-twist coupling is extended to include the influence of hygrothermal stresses. A closed-form expression for the twist associated with the curing stresses is derived. 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-ply laminated composite strips made of a graphite/cyanate material system is manufactured and tested. A custom-made 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 nonlinear axial force-twist behavior, and the analytical predictions are in close agreement with test data and a geometrically nonlinear finite element simulation.