ABSTRACT of the Doctoral Thesis

## Modeling of Matrix Damage in Particle Reinforced Ductile Matrix Composites

### by Thomas Drabek (2005)

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.

revised 050128 (hjb)