Numerical modeling of the damage evolution in an aluminum alloy reinforced bidirectionally by ceramic fibers

It is expected that the application range of metal matrix composites (MMCs) will strongly increase within the following years because of their usability in the lightweight construction. Therefore the complex deformation and damaging behavior of this class of material have to be clarified more closely. The current study intends to contribute to this by numerically investigating the mechanical cyclic behavior of an aluminum alloy reinforced bidirectionally by continuous SiC-fibers. In the first instance a three-dimensional unit cell can be derived by assuming a geometrical idealization of the fiber arrangement. This unit cell can be analyzed representatively for the whole composite by using the finite element method (FEM). The metallic matrix in the composite is modeled by a comprehensive material model which includes a coupled viscoplastic-damaging law. Special emphasis is placed on the material behavior under cyclic loads. Therefore the material law was complemented by a transition flow potential (TFP) which permits an improved description in the elastic–inelastic transition range. In order to approximate the real behavior of the composite as realistically as possible, cooling processes during manufacture have to be considered because they induce an inhomogeneous residual stress state in the composite and therefore have a significant influence on the stress–strain response of the composite. Various low cycle fatigue loads with different strain amplitudes show a continuous shift and a narrowing of the stress–strain hysteresis. The extent of inelastic deformation and damage rises significantly with increasing external loading amplitude. These damage phenomena are concentrated in the transversely loaded ply of the composite. Also the fiber volume fraction has a great influence on the deformation behavior of the composite. Here a strong incline of damage can be observed with increasing fiber volume fraction.