Aj. Fletcher et Jl. Oakeshott, THERMAL RESIDUAL MICROSTRESS GENERATION DURING THE PROCESSING OF UNIDIRECTIONAL CARBON-FIBER EPOXY-RESIN COMPOSITES - RANDOM FIBER ARRAYS, Composites, 25(8), 1994, pp. 806-813
Finite element models are developed to predict the thermal residual st
resses generated during the processing of carbon fibre/epoxy resin com
posites. A previous analysis that assumed regular arrays of fibres is
extended to include random fibre arrays, which are thought to be more
appropriate to the actual fibre distributions. The stresses are local
to single fibres under conditions of plane strain. Initially a hypothe
tical distribution is assumed which is intermediate between a hexagona
l and square array. This model consists of a representative selection
of the unit cells used in the analysis of the regular fibre arrays. Th
e fibre volume fraction of the model is 27% and the fibre separation r
anges from 1.0 to 12.0 mum. Subsequently a computer program is used to
generate random fibre arrays and a region local to a single fibre in
a 50% fibre volume fraction array is meshed for finite element analysi
s. The results are compared with those obtained assuming regular fibre
arrays. Observations are made also of actual fibre arrays under an op
tical microscope; these are compared with the fibre arrays assumed in
the modelling, The change from a regular to a random arrangement gener
ally increases the maximum tensile stress produced in the epoxy resin.
This tends to occur at positions within the smallest gap between two
fibres.