Numerical investigation of low cycle fatigue of aluminium reinforced by SiC–fibres

Abstract

Due to complexity the analysis of low cycle fatigue behaviour of long fibre reinforced metal matrix composites needs to take into consideration viscoplastic deformation and damage of the matrix, damage deactivation processes and manufacture residual stresses. Therefore, a comprehensive material model especially feasible for the description of cyclic material behaviour is presented for the metallic matrix. This model not only takes into account damage treated by means of the continuum damage mechanics. In addition, a final failure criterion allows the consideration of the crack path in the matrix of the composite. As multidirectional laminates show a much more complex damaging behaviour than unidirectional composites do, a bi-directional fibre arrangement is investigated. Therefore a three-dimensional finite element analysis is necessary to examine such types of composites. Premising the presented material model not only the development of continuous damage in the composite can be computed for various external loadings. Cracks following the continuous damage process grow parallel and circumferentially to the fibre in the off–axis layer. Therefore, it can be stated that the fatigue behaviour is strongly influenced by plies perpendicularly loaded. The damage and crack process shows also strong effects on the macroscopic mechanical behaviour of the composite such as a decrease of the absolute values of maximum and minimum stresses and a loss of unloading modulus.