If we hit them with enough force, they will obviously shatter. But what about from every day use? Does every little bump slowly crack them with micro-fractures that will build up over time, or do they have some form of elasticity or other kind of self repair?
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Generally speaking, there is a minimum amount of stress that is needed to get a material to break. Normal use stays within those limits. One of your guesses is correct as well: even seemingly rigid materials accommodate some degree of elastic deformation.
Very short answer, generally no.
To try to put materials science into eli5:
When you subject a material to a force, three things happen, in order, as force increases.
1. Elastic deformation. This is fully recoverable; the object will return to it’s initial state with no change.
2. Plastic deformation. This is permanent. Since elastic deformation occurred first, that *part* recovers, but the plastic deformation remains. This is why when you bend a paperclip, it springs back partially. This also ‘works’ the material, which builds up stresses and the like. This is why you can bend a paperclip back and forth until it eventually breaks.
3. Failure. There are different types, but this is self-explanatory for our purposes.
Different materials have different “stress strain curves” that describe how resistant they are to deformation, and how large each region is. Broadly speaking, the difference between metal and ceramic is that metals are less resistant to force, but have larger elastic and plastic regions, and fail more gradually, while a ceramic resists force a lot (thus deforming very little), right up until you hit the limit and it shatters. The plastic deformation region is small.
So the minor bumps and whatnot that ceramics are subjected to are all in the ‘elastic’ region (and the properties of ceramics mean the actual deformation is very small). There aren’t likely to be any micro-stresses building up, because it’s very unlikely to put a “just right” amount of force onto a ceramic to deform it plasticly without going over and shattering it.
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