Abstract
The local structure and strength distribution for test pieces of a composite containing fibrous material (aramid fiber) in the powder matrix (calcium carbonate and thermosetting resin) have been evaluated by using an elaborate drilling machine with a load cell and a distance sensor. The drilling resistance curve of the normal load measured under the optimal operating conditions sensitively reflected the variation of the inner structure of the composite, such as the dispersion degree of fiber, the total homogeneity, the void and crack, the packing state, the boundary of the granules, and so forth. Three types of granules prepared by different processes were molded into test pieces under the various conditions. Comparing the drilling characteristic curves with the mechanical properties of the test pieces, it was shown that the fuzzy granular-core-mixture covered with soft powder shell is a suitable raw material for molding. It was also confirmed that leaving adequate through-openings between the boundaries of granules and the internal structure of each granule is preferrable for releasing the gaseous components from the green molded test pieces up to the intermediate stage of thermal molding process.
