Investigation of grinding mechanism of a 2D Cf/C-SiC composite by single-grain scratching

A series of single-grain scratching experiments are conducted to understand the grinding mechanism of 2D carbon fibre reinforced carbon silicon carbide composite (2D Cf/C-SiC). On the basis of the woven and laminated structure of the fibre bundles, three typical surfaces (SA, SB, SC) are selected and scratched under various combinations of scratching speed and depth. Three cut-in modes which are defined according to the direction of grain motion in relation to the axis of the fibres, namely longitudinal (parallel to), transverse (perpendicular to) and normal (circle dot). The scratching forces (SFs) of all tested surfaces fluctuate periodically. The peak SFs under the different cut-in modes follow the order of circle dot > perpendicular to > parallel to. The averaged SFs on the three surfaces are generally ranked as SB > SA > SC. Under all tested scratching conditions, the composite is removed by the brittle mode, but the chipping affected width depends on the cut-in mode. Fibre bundles scratched under perpendicular to and parallel to tend to be removed as a block by either peel-off or push-off, especially on the lamination plane. All these findings explain the grinding results obtained in previous related researchs. Besides the fibre orientation and woven structure, the lamination factor must also be considered. For a given cut-in mode, the SF on the lamination plane is the lowest, which agrees with the previous result that the grinding force on the lamination plane is lower than that on any other surface. The results presented herein help in improving the collective understanding of the grinding mechanism of C/SiC composites.