Britannica
Sources used in this answer
How do fibres and whiskers make ceramic composites tougher?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
advanced ceramics
Steps in doctor blading, a tape-casting process employed in the production of ceramic films. Ceramic powder and solvent are mixed to form a slurry, which is treated with various additives and binders, homogenized, and then pumped directly to a tape-casting machine. There the slurry is continuously cast onto the surface of a moving carrier film. The edge of a smooth knife, generally called a doctor blade, spreads the slurry onto the carrier film at a specified thickness, thereby generating a flexible tape. Heat lamps gently evaporate the solvent, and the dry tape is peeled away from the carrier film and rolled onto a take-up reel for additional processing.
Fibres and whiskers enhance the toughness of ceramic-matrix composites primarily by altering the way cracks propagate through the material. When a crack advances, these reinforcements act to impede its progress through two main mechanisms:
- Crack Deflection: The presence of fibres or whiskers forces the crack to deviate from a straight path. This deflection increases the total fracture surface area, which requires more energy to create and thus slows the crack's growth.1
- Crack Bridging: Particles or fibres located behind the advancing crack tip span across the crack, exerting a force that tends to hold the crack closed. This bridging effect absorbs energy and provides significant resistance to further propagation.1
By combining these effects, these composites achieve much greater energy absorption compared to conventional ceramics, which are inherently brittle. While these reinforcements significantly improve fracture toughness, they can be susceptible to high-temperature oxidation, which may cause the material to revert to brittle behavior in extreme environments.1