The presence of micro cracks on the glass surface (called Griffith’s micro cracks) makes glass breakable under tension or impact. Such micro cracks are unavoidable as the glass surface comes under tension while cooling from a high temperature into various shapes. However, one can increase its impact resistance by various methods, so it can withstand even the impact of a bullet. The idea is to remove the surface micro cracks by chemical etching, or putting the glass surface under compression by physical or chemical toughening. One can even laminate two such toughened glass plates with resin in-between. These glasses are unbreakable, but when the threshold value is very high, it eventually breaks or cracks.
Tags Glass breakable under tension Glass surface Glass surface under compression Griffiths micro cracks High temperature Impact Impact of a bullet Increase impact resistance Micro cracks Micro Cracks by chemical etching Physical or chemical toughening Presence of micro cracks Resin Toughened glass plates Unbreakable Under tension while cooling
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