Why is glass brittle?

Question

What is it about the molecular structure of a typical glass (such as soda-lime glass) that makes it brittle?

Answer 1

If you are talking about regular soda-lime glass, the reason why it is brittle is because its molecular structure resembles that of a liquid. HOWEVER, it does not have a liquid structure. Glass is composed of tetrahedral crystals. That these crystals did not achieve regular, repeating crystalline structure does not mean glass is a permanent liquid. My Glass Ceramics prof nearly shot me for saying that in class one day.

But that's exactly it: Glass is brittle because it does not have good large-area orderly crystalline structure. If it did, it would be like sheetmetal steel, where it dents and deforms instead of shattering.

I would like to point out something else though: The strongest fiber ever tested was a glass fiber drawn and tested in an inert atmosphere. Also, you can take a glass fiber by the ends and bend it into a circle, much like any metal wire. Hence it is elastic. BUT if you touch that same fiber in several places, then try to bend it again it will shatter in your hands.

Answer 2

Hi. Glass does not freeze in the normal sense. It just flows more and more slowly. If stiffens because of this. Glass remains quite flexible as evidenced by small fibers

Answer 3

A simple way to know if its brittle is if it breaks easily. Non brittle materials go through deformation before failing while brittle materials simply break.

Answer 4

because it's shear strength is much less than it's bending strength ( a discussion in Strength of material)

Answer 5

havent a clue sorry!