Formulation of Spectral Stiffness Microplane Model for Uni-Directional Composite

Abstract

This thesis presents a general constitutive model to simulate the orthotropic stiffness, pre-peak nonlinearity, failure envelopes, and the post-peak softening and fracture behaviors of uni-directional composites. The framework of the microplane model is adopted and the constitutive laws are formulated in terms of stress and strain vectors acting on microplanes with different orientation. The model exploits the spectral decomposition of the transversely isotropic stiffness matrix to define orthogonal strain modes at the microplane level. A variational approach is applied to relate the microplane stresses to the continuum tensor at the macroscopic sacle. Following the formulation, a generic 2mm cube is used to perform calibration and validation to confirm with the experimental results.