Chapter 3.13 - Predicting the nonlinear response and progressive failure of composite laminates

Abstract

The chapter presents a comprehensive comparison of laminate failure models, which is established to assess the state of-the-art in laminate modeling technologies on an international level (known as the Worldwide Failure Olympics Exercise). It represents one contribution (called Part A of the Exercise) to the exercise, where predictions for laminate response and the failure behavior of various laminates, such as specific carbon- and glass-fiber-reinforced epoxy laminates under a broad range of loading conditions are made. The chapter describes a method for predicting the nonlinear stress/strain response and the failure behavior of composite laminates. Predictions are based on an incremental formulation of a well established three-dimensional laminated media analysis coupled with a progressive-ply failure methodology. Nonlinear lamina constitutive relations for the composites are represented using the Ramberg–Osgood equation. Piece-wise linear increments in laminate stress and strain are calculated and superimposed to formulate the overall effective nonlinear response. Individual ply stresses and strains are monitored to calculate instantaneous ply stiffnesses for the incremental solution and to establish ply failure levels. The progressive-ply failure approach allows for stress unloading in a ply and discrimination of the various potential modes of failure. The chapter presents laminate response and failure predictions for 14 different cases. The cases include prediction of the effective nonlinear stress vs. strain responses of laminates and initial and final ply failure envelope predictions under multiaxial loading.