ABSTRACT
The actual composite usually consists of short fibres dispersed in the matrix, of which at least some are at an angle with respect to the load orientation. The contribution of such short, inclined fibres to the mechanical properties of the composite is smaller than that of long fibres oriented parallel to the load, i.e. the efficiency of the short and inclined fibres is less. The efficiency of fibre reinforcement can be judged on the basis of two criteria: the enhancement in strength, and the enhancement in toughness of the composite, compared with the brittle matrix. These effects depend upon the fibre length, the orientation of the fibres, and the fibre-matrix shear bond strength. These three factors are not independent, since the effects of both fibre length and orientation are highly sensitive to the bond. A further complication in the treatment of fibre efficiency is that parameters which enhance tensile strength do not necessarily lead to higher toughness.
