InelasticRev3.doc 2/13/02 1 An Inelastic Damage Model for Fiber Reinforced Laminates Ever J. Barbero 1 and Paolo Lonetti 2 Abstract A new model for damage behavior of polymer matrix composite laminates is presented. The model is developed for an individual lamina, and then assembled to describe the nonlinear behavior of the laminate. The model predicts the inelastic effects as reduction of stiffness and increments of damage and unrecoverable deformation. The model is defined using Continuous Damage Mechanics coupled with Classical Thermodynamic Theory. Unrecoverable deformations and Damage are coupled by the concept of effective stress. New expressions of damage and unrecoverable deformation domains are presented so that the number of model parameters is small. Furthermore, model parameters are obtained from existing test data for unidirectional laminae, supplemented by cyclic shear stress-strain data. Comparison with lamina and laminate test data are presented to demonstrate the ability of the model to predict the observed behavior. 1 Introduction The advancing use of polymer matrix composites (PMC) in applications with long life cycles requires better analysis techniques to predict material degradation and failure. Experimental results show marked nonlinear effects when a single lamina is loaded by shear [1, 2]. Instead, lower non-linearity appears when the loading is along the fiber direction or transverse to it. The most common modes of failure of PMCs are fiber breakage, fiber matrix debonding, matrix cracks, and fiber kinking. Fabrication of PMCs 1 Professor, Mechanical and Aerospace Engineering, West Virginia University, Morgantown, WV 26506-6106. ebarbero@wvu.edu. 2 PhD candidate, Department of Structural Engineering, University of Calabria, Italy