Reinforcing Mechanism by Small Diameter Fiber in Short Fiber Composite

Influence of fiber diameter on the mechanical properties of short fiber composite was studied by using smaller diameter fibers than conventional ones. Strength and toughness of the composite reinforced with the small diameter fibers were improved, compared to those of the composite reinforced with the conventional ones, except for extremely small diameter fibers. Thus, there exists the maximum value for the strength and toughness for the optimum fiber diameter. This result indicates that there is an optimum condition for the reinforcing effectiveness by the small diameter fibers. In order to analyze the reinforc ing mechanism by the small diameter fibers, fracture mechanism of the composite was studied by an acoustic emission analysis, in-situ SEM observation of failure process, and observation of plastic deformation of the matrix. As a result, initiation and propagation of microcracks occurring at fiber/matrix interface were found to be strongly suppressed by using the small diameter fibers, compared with those in the conventional composite. A model for explaining the reinforcing mechanism by the small diameter fibers was pro posed, which can well explain the presence of the optimum fiber diameter, resulting in the highest reinforcing effectiveness for the composite.