Comparison of Axisymmetric and Planar Fracture Mechanics Models for Fiber-Reinforced Composites

Many fracture mechanics models based on either 3D-axisymmetric or 2D-planar models are used to predict mechanical parameters of composites, such as their fracture toughness, matrix crack initiation stress and stiffness. In this study, fracture mechanics models for a composite geometry with a matrix crack under uniform crack pressure are developed using both 3D-axisymmetric and 2D-planar assumptions. Three critical parameters, namely the stress intensity factor at the crack tips, the maximum crack-opening displacements and the stress ratios at the interface, which are used to quantify the above mechanical parameters of a composite, are compared for the two models. The results for the stress ratios at the interface, which are used to predict the path of crack propagation near a fiber-matrix interface, are close to each other. However, the results for the stress intensity factor and the crack-opening displacements, which are used to quantify matrix crack initiation stress and damaged composite longitudinal stiffness, differ considerably.