The disclosure describes in some examples a technique that includes the disclosure describes a technique that includes depositing a carbon powder and a resin powder on a surface of a fiber preform, where the fiber preform includes a plurality of fibers and defines interstitial spaces between the plurality of fibers, and vibrating the fiber preform to allow the carbon powder and the resin powder to infiltrate the interstitial spaces between the plurality of fibers of the fiber preform to form an infiltrated preform.