Viscous flow of aligned composites

Abstract

The case is considered of an aligned composite subjected to tensile creep in the direction of the fibres. A geometrical argument shows that shear strain in the composite is amplified l/2s times compared with unsupported matrix, where l/2s ∼ aspect ratio of the inter-fibre spaces. The shear stress is amplified (l/2s)^1/n times, where n is the exponent in the matrix creep law. Consequently the rate of energy expenditure is amplified V _m(1/2s)^1+1/n times, as is therefore the tensile flow resistance of the composite (V _m is the volume fraction of matrix). The potential increase in flow resistance is thus enormous. However, the fibre end-stress, which is calculated, ∝ fibre diameter, and may be large enough to initiate rupture unless the fibres are very thin (e.g. 1 μm diameter). The tensile load is roughly equally divided between matrix and fibres irrespective of volume fractions.