Two- and three-dimensional microstructure-based finite-element
simulations are used to investigate the thermal expansion behavior
and inherent residual stresses of low thermal expansion ceramic
composites. Such composites have myriad applications, for example,
in precision optical devices, turbine engine heat exchangers, and
domestic cook-tops. Typically, they are a polycrystalline composite
of a negative thermal expansion material[e.g., beta-eucryptite (LiAlSiO4)]
with small amounts of a positive thermal expansion ceramic [e.g., alumina].
As such, they develop very large thermally-induced residual stresses,
and hence stored elastic strain energy in the microstructure, which
can lead to micro- and macro-cracking. The nature and distribution
of these stresses as well as the thermal expansion behavior are
studied for composite compositions with varying beta-eucryptite to
alumina ratios. Topological invariants of the residual stress
isosurfaces are used to characterize the stress distributions and
to identify potential fracture initiation sites.