Scope:

ASTM C1525 test is useful for material development, quality control, and durability assessment of advanced ceramics with regards to thermal shock.

Thermal shock is the stress experienced by materials with extreme and rapid changes in temperature. The surface layers of the material might contract against the inner layers, leading to the development of tensile stress and the propagation of cracks. The ability of a material to endure such temperature changes without changes in its properties is called Thermal Shock Resistance.

In many engineering applications, materials must perform across a broad range of temperatures, and ceramics are an excellent choice for such engineering applications because they show excellent resistance against extreme temperatures.

This test cannot determine the thermal stresses developed due to a steady-state temperature difference or thermal expansion mismatch between joined bodies. The test method does not determine the resistance of ceramic material to repeated thermal shocks either. Since the determination of the thermal shock resistance is performed by evaluating retained strength, the method is not suitable for ceramic components but specimens cut from components may be used.

Test Procedure:

In ASTM C1525, a ceramic sample is given a thermal shock by heating it and instantly quenching it with a cool water bath, and then the effect of the thermal shock is assessed by measuring the reduction in flexural strength.

Data:

The flexural strength of the prismatic test specimens is calculated as follows: 

S = 3P (L₀ – L₁)/2bd²

Where, 

S = flexural strength, 

P = measured fracture load,

(L₀ – L₁) = outer and inner spans, respectively, m, 

b = test specimen width, m, and 

d= test specimen height, m.

The strength of cylindrical test specimens is calculated as follows: 

S = P (L₀ – L₁)/πr³