Study on the Grinding Mechanism of Glass Fiber Reinforced Plastics

In order to clarify the grinding mechanism of polymer matrix composites, special test specimens were provided. The test specimen is such one that glass yarns are unidirectionally embedded at even interval on the middle plane of thick of a polymer matrix plate. The end face perpendicular to the plane on which glass yarns are lined up is ground in the direction at various angle from the direction of glass yarn. The aspects of the cut end of the glass yarn near the ground surface are observed microscopically, and relations between the angle of the direction of yarn and the topography of the ground surface are investigated. Following results are obtained. (1) The microscopically observed aspects of failure of the end of yarns near the ground surfaces are classified into two modes by the direction of yarn measured counterclockwise from the direction of grinding. In the range from 0 rad. to π/3 rad. of the angle, the failure of the end of yarn is comparatively deep, and spreads over the whole section of the yarn. In the range from π/2 rad. to π rad. of the angle, the failure of the end of the yarn is comparatively shallow, and random in the depth and the spread. (2) The topography is also classified into two types by the above angle. In the range from 0 rad. to π/3 rad. of the angle, the end of yarn forms a hollow pit, and in the range from π/2 rad. to π rad., the end of yarn forms a swollen proturberance. (3) The above facts are well understood by considering the digging up action of the grinding grain in the range from 0 rad. to π/3 rad., and the push down action of the grain in the range from π/2 rad. to π rad. in the grinding process.