| In order to provide improved capabilities for predicting nonlinear composite material behavior, a new three-dimensional micromechanical model is presented. The model formulation is based on a unit cell or representative volume element approach where the coupling effects between normal and shear stresses within the unit cell are relaxed. The formulation lends itself very well to the inclusion of nonlinear behavior while maintaining the three-dimensional effects.; The present capabilities of the model include both unidirectional and laminated composite layups with various types of nonlinear analysis such as a thermoelastic-plastic analysis employing the Prandtl-Reuss flow relations, a thermo-viscoplastic analysis using Bodner-Partom unified constitutive theory, and an interfacial damage progression scheme based on a statistical interfacial failure criteria. Such nonlinearities are critical factors during thermomechanical fatigue (TMF) loading of high temperature composites.; Solutions were obtained and extensive comparisons performed with existing micromechanics models, finite element analysis, and experiment with excellent results. In addition, the analysis was developed to require minimal computer resources. For instance, the majority of problems may be accomplished on a personal computer in a matter of seconds. Therefore, the present analysis represents a formulation that accounts for many nonlinearities that heretofore have been very difficult or in some cases impossible to perform with previous micro-mechanics models or the finite element method. |
