Hello, I am choosing glasses for a novel solar cell design, and part of the criteria is if the glass will be able to withstand hail and other things (?) falling from the sky, since this glass will be the cover glass for the entire solar cell. I can gather information on the glass including Knoop/Moh's hardness, Young's modulus, etc., but 1. I'm not sure which of these structural properties translates to being able to withstand things like hail and 2. If it's hardness, how hard is hard enough/how can I determine this? Any help is greatly appreciated. Thanks.