A Constitutive Theory of Matrix Cracking and Interply Delamination in Orthotropic Laminated Composites

The response behavior of an orthotropic laminated composite weakened by matrix cracking and delamination under mechanical loading is modeled herein by a com prehensive theory within the general framework of damage mechanics. The two different damage modes of matrix cracking and interply delamination are represented by two sym metric second rank tensors. Their influence on constitutive relations of the damaged com posite is obtained via the basic principles of continuum mechanics and the theory of in- variants. As the two damage tensors are independent of loading history and hence may be taken as internal variables, the equations governing their evolution are subsequently derived based on the concepts of damage dissipative potential and damage surface in the space of generalized thermodynamic forces. The identification of unknown material pa rameters through simple tests is discussed. Comparison between the present analytical prediction and the experimental measurement from others is also given.