Geometric non-linear analysis of composite laminated plates with initial imperfection under end shortening, using two versions of finite strip method

Description is given of both spline and semi-analytical finite strip method for predicting the post-buckling response of rectangular composite laminated plates with initial imperfections, when subjected to progressive end shortening. The initial imperfections are all assumed to be of the sinusoidal shape in the longitudinal direction, and of different shapes in the transverse direction. The laminates are simply supported out of their plane at the loaded ends as well as unloaded edges. The in-plane lateral expansion υ is allowed all around the plates. The plates are assumed to be thin so that the analysis can be carried out based on the classical plate theory. Geometric non-linearity is introduced in the strain-displacement equations in the manner of the von Karman assumptions. The formulations of the finite strip methods are based on the concept of the principle of the minimum potential energy. The Newton-Raphson method is used to solve the non-linear equilibrium equations. A number of applications involving plates with different shapes of initial imperfections are described to investigate the capability of both versions of finite strip method.