EFFECT OF FIBER LENGTH ON THE TENSILE STRENGTH OF GLASS/EPOXY AND GLASS/POLYESTER COMPOSITES

Abstract

In the short glass fiber-resin composites, the shear strength at fiber-matrix interface is one of the dominating factors for the reinforcement effect. In this paper, a method was devised to determine the shear strength accurately, taking the strength distribution of glass fiber into consideration. The values, calculated for the tensile strength of composites by this method, were in better agreement with experimental ones than those calculated under the assumption of the constant strength of glass fiber.The tensile strength of composites increases with the increase in the aspect ratio of reinforcing fiber. The increasing trend is almost the same regardless of the kind of matrix, the nature of interfacial treatment and the environmental temperature. When the composites are reinforced with random-planar orientation of short glass fibers of 1.5 times the mean critical fiber length, the tensile strength of composites reaches about 90% of the theoretical strength of composite reinforced with continuous glass fiber. Reinforcing with glass fibers of 5 times the length, the tensile strength reaches about 97% of theoretical one. However, it is adequate to use short fibers of 1.5_??_2.0 times the mean critical fiber length, if the ease of the moulding process is taken into consideration.