Three-dimensional variational analysis of composite structures using bernstein polynomial approximations. Report 2

The application of the previously developed 3D varionational analysis approach to the investigation of crack propagation in composite bonded joints is presented. In this application, the propagation of three different types of a 2D planar crack (adhesive, cohesive, and interfacial) is modeled by relaxing the respective continuity conditions for displacements between adjacent bricks in the mosaic structure. The crack propagation process is then characterized by the release rate of the total potential energy between two consecutive states of the mosaic body with different crack lengths. Numerical examples illustrate the 3D analysis of double-lap adhesively bonded joints with unidirectional and cross-ply laminated composite adherends. The numerical results provide an illustration of various characteristics of the crack propagation process. The values of the ultimate failure load predicted by analyzing the initial stage of crack propagation are found to be in a good agreement with experimental data. (Sample material: AS4/3501-6 carbon-epoxy composites.)