Stability Analysis of Thick-Section Composite Cylinders Under Hydrostatic Pressure Including Three-Dimensional Effects and Nonlinear Material Response

Abstract

Recent studies of thick-section laminated composite materials and structures have suggested that there is a need for three-dimensional (3-D) structural analysis methods which include the nonlinear material response of the constituents. The work described in this paper integrates a 3-D micromechanics-based nonlinear constitutive model for laminated composite materials into 3-D structural analyses performed with the ABAQUS general purpose finite element code. The nonlinear model and its incorporation into ABAQUS are described. The method is demonstrated through 3-D stability analyses of thick, unstiffened AS4/3501-6 carbon/epoxy circular cylinders under external hydrostatic pressure. The results of two-dimensional (2-D) shell finite element analyses of these cylinders are also presented for comparison. The cylinders analyzed are geometrically identical and are subjected to the same loading and boundary conditions. Five different ply layups are considered, including cross-ply, quasi-isotropic, and [±45°]. Modeling the nonlinear material response is found to reduce the predicted cylinder collapse load by up to 50% when layers oriented at ±45° to the cylinder axis are present in the laminate. The role of material nonlinearity in the plane of the laminate versus through-thickness nonlinearity is discussed for the cylinders analyzed.