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

Abstract

In the current study the thermomechanical behavior of an aluminum alloy reinforced bidirectionally with SiC-fibers is numerically investigated by using the finite element method. A three-dimensional unit cell can be derived from a geometrical idealization of the fiber arrangement. Special emphasis is placed on the inelastic material behavior of the metallic matrix because of its strong influence on the composite behavior. Therefore a comprehensive viscoplastic unified model is proposed, which permits an improved material description by using the transition flow potential (TFP). Cooling processes during manufacture induce a pronounced inhomogeneous residual stress state 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 cyclical mechanical loading with a constant strain amplitude simulations show an increase of the residual strain (ratchetting) and a narrowing of the hysteresis loop with increasing cycle number. Residual stresses induced during manufacture cause an asymmetric hysteresis with varying magnitude and temporal development of maximum and minimum averaged stresses. Cyclical behavior of composites is strongly influenced by a superposed thermal loading, whereby it must be distinguished whether the thermal load is in-phase or out-of-phase to the mechanical load.