Effect of a SiC whisker formation on the densification of Tyranno SA/SiC composites fabricated by the CVI process

SiC whiskers were introduced into the SiC fiber preform by the CVI method with and without an Fe catalyst. The whisker growing process resulted in a composite with a higher density than the conventional-CVI composite when assuming similar infiltration times. Multiple cycles of the whisker growing and the matrix infiltration steps were required to effectively reduce the size of the interbundle voids, due to the limited length of the whiskers grown without the catalyst. Although the adoption of the metallic catalyst increased the length and the homogeneity of the whiskers, the early clogging of the composite surface restricted the effective infiltration of the center region of the composite. A gradient of the whisker concentration in the thickness direction was suggested for a uniform densification.