Abstract
The aim of this contribution is to give the procedure of the digestion method for the determination of fiber content of metal matrix composites. In order to discuss the method, silicon carbide whisker reinforced aluminum alloys were digested by some solutions. The suitable acidic or basic solution to digest the matrix and the procedure to clean the collected fiber depend upon the chemical characteristics of the fiber and the matrix. Some alloying elemets in the matrix are insoluble in the digestion solutions. And some fragment of the fiber may pass through the filter to collect the fiber. Accordingly, it is not enough to correct for the weight loss of the fiber by the digestion procedure, as ASTM D 3553. But these are also necessary to correct for the insoluble-filtered fraction in the matrix and to correct for collecting efficiency of the fiber by the filter. The opening size of the filter to collect the fiber should be determined from the size of the fiber diameter or fragment in the composite being tested. The used silicon carbide whisker is oxidized in dry air below 400°C accompanied by a weight increase. For the precise determination of the fiber content of metal matrix composites by digestion method, corrections should be done for the insoluble-filtered fraction in the matrix and the weight change of the fiber during the procedures of digestion, filtering and drying.
