Mechanical properties of glass【Material Science】

【Answer】The theoretical tensile strength limit of glass is 12000Mpa, the actual strength is only 1/400-1/200 of the theoretical strength, generally 30-60Mpa, and the compressive strength of glass is about 700-1000Mpa. Various unavoidable defects in the glass (raw material purity, crystallization process, mineral impurities, uneven chemical elements, etc.) cause stress concentration or weak links, and the larger the size of the glass specimen, the more defects exist. The effect of defects on tensile strength is very significant, and the effect on compressive strength is small. Foreign impurities and ripples (chemically inhomogeneous parts) caused by the process have a significant impact on the strength of the glass. The strength of glass remains virtually unchanged in the range of -50°C to +70°C.

Brittleness is the main disadvantage of glass. The brittleness index E of glass is 1300-1500 (polycarbonate is 0.4-0.6, steel is 400-460, concrete is 4200-9350). A larger E value indicates greater brittleness. The brittleness of the glass can also be determined by impact tests. (See: High impact resistance)

In practical applications, glass products are often subjected to bending, tensile and impact stress, and less subject to compressive stress, so the compressive strength of glass is of less significance. The main indicators of the mechanical properties of glass are tensile strength and brittleness, both of which are weak points of glass.