Abstract :
Composite materials demonstrate a considerable
extent of heterogeneity. A non-uniform spatial distribution
of reinforcement results in variations of local properties of
fibrous laminates. This non-uniformity not only affects
effective properties of composite materials but is also a
crucial factor in initiation and development of damage and
fracture processes that are also spatially non-uniform. Such
randomness in microstructure and in failure evolution is
responsible for non-uniform distributions of stresses in
composite specimens even under externally uniform loading,
resulting, for instance, in a random distribution of matrix
cracks in cross-ply laminates. The paper deals with statistical
features of a distribution of carbon fibres in a transversal
cross-sectional area in a unidirectional composite with
epoxy matrix, based on various approaches used to quantify
its microscopic randomness. A random character of the
fibres’ distribution results in fluctuations of local elastic
moduli in composites, the bounds of which depend on the
characteristic length scale. A lattice model to study damage
and fracture evolution in laminates, linking randomness of
microstructure with macroscopic properties, is discussed.
An example of simulations of matrix cracking in a carbon
fibre/epoxy cross-ply laminate is given.
