MICROMECHANICS-BASED STRUCTURAL-ANALYSIS OF THICK LAMINATED COMPOSITES

Thick filament wound cylinders, or local regions in structural laminat es around cut-outs, fasteners or stiffeners may require three-dimensio nal (3D) analysis and evaluation, in order to fully characterize behav ior and evaluate safety margins. This paper describes a particular app roach to the 3D structural-level analysis of thick laminated composite s that utilizes homogenization concepts and standard displacement-base d finite element modeling. Hierarchical material modeling forms the ba sis of the procedure. The material model consists of two modules: (1) a micro-model of a unidirectional lamina, containing the basic 3D cons titutive information for fiber and matrix constituents; and (2) a subl aminate model that enforces equilibrium of tractions between laminae, and delivers 3D homogenized stresses and strains and material tangent stiffnesses. This integrated approach provides the information require d for evaluating damage and failure conditions at the microstructural level, and is essential for nonlinear analysis because of possible int eractions between damage and failure modes. A nonlinear elastic materi al model is formulated, as an example; this nonlinear model, which is suitable for epoxy matrices, has been successfully implemented in a st andard finite element code and used quite extensively. However, only e lastic analysis results are presented, because the important character istics of the modeling approach are clearly revealed in this setting. Comparisons are made between material model predictions and analytical , numerical, and experimental results for a unidirectional lamina, a t hick laminate, and a thick cylinder under compression and bending. The se results show that the accuracy of the procedure for thick laminates is quite satisfactory for practical purposes.