Inorganic glasses are one of the strongest known materials.

Strength of Inorganic Glasses

The intrinsic inert strength of oxide glasses is among the highest of any known materials:

silica ~ 14 GPa

'window glass' - soda lime silica ~ 10 GPa.

The above is not commonly known or appreciated.
What is commonly known is that the 'practical', or commonly encountered strength of both of these glasses is ~ 50-70 MPa.

On the other hand, the now well-known lightguide fibers being installed in local telephone networks, does have and extremely high strength: ~5.5 GPa over MOST of its length.

It is clear that the reason for this enormous 'discrepancy' is that at some point, the glass surface has been 'mechanically damaged'.

Our task is then 3-fold:

1. Understand the fundamental parameters (composition, etc.) that control the inert intrinsic strength.

2. Understand the factors that influence the susceptibility or resistance to mechanical damge (composition, etc.).

3. Understand/develop techniques to 'protect' the glass surface from this mechanical damage (coatings, chemical and thermal tempering, cladding, lamination).