Modeling and numerical simulation of the thermomechanical cyclical behavior of a cross-ply MMC

In the current study the thermomechanical behavior of an aluminum alloy rei nforced bidirectionally with SiC-fibers is numerically investigated by usin g the finite element method. A three-dimensional unit cell can be derived f rom a geometrical idealization of the fiber arrangement. Special emphasis i s placed on the inelastic material behavior of the metallic matrix because of its strong influence on the composite behavior. Therefore a comprehensiv e viscoplastic unified model is proposed, which permits an improved materia l description by using the transition flow potential (TFP). Cooling process es during manufacture induce a pronounced inhomogeneous residual stress sta te in the composite resulting in local inelastic matrix deformation. These stresses have a considerable influence on the mechanical behavior, so that different attitudes under tension and compression can be observed. Under cy clical mechanical loading with a constant strain amplitude simulations show an increase of the residual strain (ratchetting) and a narrowing of the hy steresis loop with increasing cycle number. Residual stresses induced durin g manufacture cause an asymmetric hysteresis with varying magnitude and tem poral development of maximum and minimum averaged stresses. Cyclical behavi or of composites is strongly influenced by a superposed thermal loading, wh ereby it must be distinguished whether the thermal load is in-phase or out- of-phase to the mechanical load. (C) 1999 Elsevier Science B.V. All rights reserved.