Question

The fracture toughness values of Ceramic Matrix Composites lie between

• A. 5 and 18 MPa\( \sqrt{m} \)
• B. 6 and 20 MPa\( \sqrt{m} \)
• C. 8 and 16 MPa\( \sqrt{m} \)
• D. 9 and 21 MPa\( \sqrt{m} \)

Hint:

CMCs have higher fracture toughness than traditional ceramics due to fiber reinforcement, making them suitable for aerospace and high-temperature applications.

Answer 1

The Correct Option is B

Fracture toughness (\( K_{IC} \)) is a material property that describes a material’s resistance to crack propagation. Ceramic Matrix Composites (CMCs) generally have higher fracture toughness than traditional ceramics due to their ability to resist crack growth through fiber reinforcement.
Step 1: Understanding the Fracture Toughness of CMCs - Traditional ceramics have low fracture toughness (\( 1-5 \) MPa\( \sqrt{m} \)), making them brittle. - CMCs are reinforced with fibers (e.g., SiC, alumina) to enhance toughness. - The fracture toughness of most CMCs falls in the range of 6 to 20 MPa\( \sqrt{m} \).


Step 2: Evaluating the Options - Option (A) - Incorrect: 5 to 18 MPa\( \sqrt{m} \) is slightly lower than the typical range.
- Option (B) - Correct: 6 to 20 MPa\( \sqrt{m} \) matches experimental values for CMCs.
- Option (C) - Incorrect: 8 to 16 MPa\( \sqrt{m} \) is too narrow.
- Option (D) - Incorrect: 9 to 21 MPa\( \sqrt{m} \) is slightly higher than the typical range.


Step 3: Conclusion Since the fracture toughness of Ceramic Matrix Composites typically lies between 6 and 20 MPa\( \sqrt{m} \), the correct answer is option (B).