ABSTRACT of the Doctoral Thesis
The present work deals with the simulation of ductile damage in metal matrix composites (MMCs) by the finite element method. The materials studied consist of a ductile matrix with embedded particulate reinforcements the size of which is of the order of a few microns. The aim of this work encompasses research on the influence of particle arrangement and size on matrix damage and, hence, the failure of the whole composite.
The observed failure modes of MMCs - matrix damage, particle fracture and interface debonding - act as local phenomena. Accordingly, an obvious modeling strategy consists in resolving the matrix as well as the reinforcements in a finite element mesh. Due to the governing length scale this kind of simulations are also known as micromechanical models. This approach provides the capability of investigating the global behavior of the material under a wide range of thermomechanical loads ("material characterization").
In order to fulfill the above task, a number of material subroutines were implemented into the commercial finite element program ABAQUS/Standard. These subroutines have the capability of describing the behavior of elastoplastic metallic materials in their undamaged as well as in their damaged states.
It is well known from the literature that such damage models in their basic form show an inherent mesh dependence as a consequence of which the results of simulations may be governed by the finite element mesh size. Because such behavior is evidently not acceptable, a nonlocal approach was applied and implemented that allows to mitigate or prevent the above problem.
This work contains a short introduction to metal matrix composites and their failure modes, a description of some important ductile damage models available from the literature, a detailed explanation of the implementation into ABAQUS/Standard for three models, and a discussion of results obtained with finite element analyses.