Composite Interlaminar Fracture Toughness: Three-Dimensional Finite-Element Modeling for Mixed Mode I, II, and Fracture

A computational method/procedure is described which can be used to simulate individual- and mixed-mode interlaminar fracture progression in fiber composite laminates. Different combinations of Modes I, II, and III fracture are simulated by varying the crack location through the specimen thickness and by selecting appropriate unsymmetric laminate configurations. The contribution of each fracture mode to strain energy release rate is determined by the local crack closure methods, while the mixed mode is determined by global variables. The strain energy release rates are plotted versus extending crack length, where slow crack growth, stable crack growth, and rapid crack growth regions are easily identified. Graphical results are presented to illustrate the effectiveness and versatility of the computational simulation for (1) evaluating mixed-mode interlaminar fracture, (2) for identifying respective dominant parameters, and (3) for selecting possible simple test methods.