ABSTRACT of the Habilitation Thesis

## Einheitszellenanalysen für unidirektional langfaserverstärkte
Metallmatrix-Verbundwerkstoffe

**(Unit cell analyses for unidirectional continuously reinforced metal matrix
composites)**
### by H.J. Böhm

*done at the*

Insitute of Light Weight Structures and Aerospace Engineering,
TU Wien, 1994

The present contribution describes a series of micromechanical studies of the
thermomechanical behavior of unidirectional metal matrix composites (MMCs).
Two-dimensional unit cell models are used, on the one hand, to compute the
effective macroscopic properties of the composites from the material behavior
of fibers and matrix, and, on the other hand, to describe the microscale
stress and strain distributions within the MMC.
The unit cells are analyzed via the Finite Element Method.

The focus of the work lies on describing the thermoelastoplastic behavior
of a composite that consists of unidirectional boron fibers embedded in
a matrix of aluminium 6061-0.
Axial, transverse and thermal loads are considered.
Of special interest are the influence of microscale residual stresses that
are generated both during the production process of the MMC and upon
surpassing the yield limit during loading as well as shakedown in the
matrix under thermomechanical loading.

The influences of different fiber arrangements on the effective material
properties of the MMC and on the microscale stresses and strains are studied
via appropriate unit cells at a given fiber volume fraction.
A marked influence of the microgeometry on the macroscopic behavior under
transverse mechanical loading and on the microfields under thermal and
transverse loading are found.
The consequences of such phase arrangement effects with respect to failure
relevant parameters in the matrix and to microstresses in the fiber-matrix
interface are discussed.

The final part of the work studies the thermomechanical properties of a
composite consisting of pure aluminium and ceramic fibers.
It is shown that the effective axial thermal expansion of continuously
reinforced unidirectional composites is dominated by the fibers once the
matrix is fully yielded.
On this basis, a combination of experiments and of micromechanical
simulations is used for determining the coefficient of thermal expansion of
the fibers, which is difficult to measure, in dependence on temperature.

revised 000413 (hjb)