Creep of multidirectionally fibre-reinforced composites

Abstract

A model for the creep of metal matrix composites multidirectionally reinforced by short fibres is proposed. The reinforcement is described by the effective stiffness tensor of a multidirectional arrangement of continuous fibres and the internal damage of the composite during creep due to fibre fragmentation is introduced by assigning a heuristic nonlinear stress–strain relationship to the fibres. Based on the model, the load partitioning between matrix and fibres is computed. The macroscopic creep behaviour is simulated for composites exhibiting different fibre orientation distributions and different heuristic nonlinear stress–strain functions. The computational results rationalize the creep behaviour of multidirectional fibre-reinforced composites. For a two-dimensional random orientation distribution, a good qualitative match between simulation and experimental results is obtained for compressive loading and for in-plane tensile loading. For loading normal to the reinforcement plane, the model overestimates the creep resistance. In this case, the formation and growth of cavities seems to govern the creep deformation of the composite.

Acknowledgements

A large portion of the work presented in this article was performed at Max Planck Institute for Metals Research and at Institut für Metallkunde, Universität Stuttgart, Stuttgart, Germany, where the authors worked until recently. G. Garcés is grateful to the Max Planck Institute for Metals Research, Stuttgart, for granting him a scholarship. Financial support by the Deutsche Forschungsgemeinschaft, Bonn, Germany, under project SFB 381/A1 is gratefully acknowledged.