Effect of residual shear strain on the cured shape of unsymmetric cross-ply thin laminates

Abstract

The warping of unsymmetrically laminated composites is induced by the thermal residual curing stress generated during the fabrication process. Most papers which have dealt with the warping of unsymmetric thin laminated composites assumed the in-plane shear strain to be negligible. However, inplane shear strain exists in certain cases for orthotropic laminates. This paper presents a new formulation including in-plane shear strain. Present results indicate that thermal residual shear strain is negligible in cases where width-to-thickness is very large or small. However, a significant amount of shear strain exists in the range of medium width-to-thickness ratio where a bifurcation point occurs. This paper investigates the effects of width-to-thickness, aspect ratio, number of layers, and stacking sequence on the shapes of the unsymmetric cross-play [0 n/90 n] T (n = 1,2…) family of laminates. Curvatures are calculated for square and rectangular laminates as using the nonlinear Newton-Raphson iteration method numerically. In some cases, numerical results are compared with experiments.