Prediction of the fatigue-damaged behaviour of Al/Al2O3 composites by a micro-macro approach

The use of very heterogeneous materials in structural components submitted to cyclic loadings, leads us to present an elastoplastic micromechanical mo del. After some revision of the homogenisation principle based on a mean fi eld theory, a non-linear kinematic and isotropic strain hardening is introd uced in the matrix. Validation is made on a Al-3.5% Cu/SiC particles and th e case of an A356/Al2O3 fibres is treated as a first application. Damage is introduced in the model by using a fibre failure criterion. It is based on the increase in the volume fraction of broken fibres as a function of the maximum principal stress in the fibre family. The damage law is identified with in situ tensile test performed inside the scanning electronic microsco pe. The number of broken fibres is determined with the applied load and the number of cycles. The model predicts the fatigue behaviour, the lost of st iffness, the volume fraction of broken fibres for different volume fraction , aspect ratio, distribution of orientation, distribution of strength of th e fibres. The effect of the mechanical fatigue properties of the matrix is also studied. (C) 2001 Elsevier Science Ltd. All rights reserved.