MICROMECHANICAL APPROACH TO THE TENSILE-STRENGTH OF UNIDIRECTIONAL COMPOSITES .1. MONOFILAMENT STRENGTH AND FIBER-MATRIX INTERACTION

This paper deals with the micromechanics of advanced composites. The c haracteristics of individual fibers, matrix, and the fiber/matrix inte rface are the most important factors for evaluating fiber-reinforced c omposite materials from a micromechanical viewpoint. To this purpose, we first developed a testing device with which the load-elongation cur ve of a monofilament can be obtained. Filament diameter was measured b y the aid of laser diffraction. Using these devices, we have tensile-t ested several kinds of monofilaments and accumulated data. The strengt h distribution agreed fairly well with the Weibull distribution. The f iber/matrix interaction was also examined with a single fiber embedded model. By measuring a fragment length, an ineffective length was calc ulated. This paper will provide the basic data to the second report in which the strength of unidirectional composites is predicted by means of computer simulation.