In one example, a method includes mixing a plurality of carbon fibers in a liquid carrier to form a mixture, depositing the carbon fiber mixture in a layer, forming a plurality of corrugations in the carbon fiber layer, and rigidifying the corrugated carbon fiber layer to form a corrugated carbon fiber preform. In another example, a method includes substantially aligning a first ridge on a first surface of a first corrugated carbon fiber preform and a first groove on a first surface of a second corrugated carbon fiber preform, bringing the first surface of the first corrugated carbon fiber preform into contact with the first surface of the second corrugated carbon fiber preform, and densifying the first corrugated carbon fiber preform and the second carbon fiber preform to bond the first corrugated carbon fiber preform and the second carbon fiber preform.