The effect of the boundary interphase on the thermomechanical behaviour of composites reinforced with short fibres

Abstract

Glass-resin composites may be considered in reality to be a multiphase system, since they incorporate not only the two main phases, but also the ‘interphase’, which is an area between fibre and matrix containing both areas of adsorption interaction in polymer surface layers into glass fibres, as well as an area of mechanical imperfections. The concept of the boundary interphase, as well as the thermomechanical properties of this interphase in metal-filled epoxies was investigated in previous studies by the authors. 1,2 It was proved that the interphase material is a viscoelastic one with different thermal properties. Furthermore it was found that, as the temperature of the composite is changing, the interphase has a dramatic effect on the overall behaviour of the composite, due to the different thermomechanical, as well as the viscoelastic properties of the interphase. On the other hand, interphase-volume fraction is a criterion of the quality of adhesion between matrix and filler. In this paper, the effect of the boundary interphase on the mechanism of the thermomechanical load transfer across the interface in the case of composites reinforced with short fibres, was investigated theoretically. In order to explain this effect, a model similar to Rosen's model with some modifications was used.