What is the typical relationship between compressive and tensile strength in ceramics?

• A. Compressive strength is typically about ten times the tensile strength.
• B. They are approximately equal.
• C. Tensile strength is higher than compressive.
• D. Compressive strength is negligible.

Answer: (A)

Ceramics are brittle and highly flaw-sensitive, so their behavior under load differs dramatically between tension and compression. In tension, any flaw acts as a crack starter; cracks open and propagate quickly, giving a relatively low tensile strength. In compression, cracks tend to close and the friction on crack faces resists further opening, allowing much higher loads to be sustained before failure. This combination leads to a typical relationship where compressive strength is about an order of magnitude higher than tensile strength, so describing the compressive strength as roughly ten times the tensile strength captures the common behavior. The other options clash with this well-known pattern: ceramics are not about equal strength in both modes, they are not stronger in tension, and their compressive strength is not negligible.