NONLINEAR ANALYSIS OF COMPOSITE LAMINATES

Nonlinear static and dynamic responses of composite laminates were investigated using the finite element method. A nine-node isoparametric quadrilateral element was developed to formulate the finite element equations for a laminated plate under initial deformations and initial stresses according to the Mindlin plate theory and von Karman large deflection assumptions. Static large deflection and postbuckling of plates, impact response of a laminate under initial stresses, free vibration and impact response of buckled composite plates, and non-linear transient and impact analyses of laminated plates with/without initial stresses were studied. In the impact analysis, a experimentally established contact law which accounts for the permanent indentation was employed to calculate the contact force. This contact law was incorporated into the finite element program to study the dynamic response of laminated composites subjected to impact of a hard object. In the nonlinear transient analysis, Newmark time integration algorithm, in conjunction with successive iterations within each time step was used. An iteration scheme with a constant coefficient matrix was used to treat the nonlinear terms. The efficiency and the accuracy of the algorithm were demonstrated for given external loadings. Numerical results were compared with those available in the literature