A two scale model for damage mechanisms during machining of carbon fibre reinforced plastics

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Due to their low density and the resulting mechanical properties, carbon fiber reinforced plastics (CFRP) are suitable for innovative lightweight design concepts. The partly heterogeneous as well as anisotropic fiber matrix structure not only influences the resultant processing result but also the different workpiece properties during the machining operation, e.g. fiber failure (FF), matrix failure (MF), fiber matrix failure (FMF) and delamination. In order to identify these complex damage mechanisms in more detail, a two scale model will be developed within the research project. The two-scale model captures the various damage mechanisms FF, MF and FMF within the framework of a mean-field method. The required mechanical characteristics of the respective type of failure are determined separately using suitable test methods at different strain rates and temperatures, thus accounting for the real stress load during the machining operation. A cohesive zone model is used for delamination which is verified based on experimental data. Subsequently, the complete model is implemented in the finite element program Abaqus to enable a macroscopic simulation of the cutting process, including the resulting damage. The simulation model is successively adapted and validated by means of real machining. A detailed description of the working relationships in the machining of CFK is provided by the developed model.