The objective of this test was to determine the compressive properties of pyrolytic graphite when loaded parallel to the a-b planes at temperatures from room temperature to 5000 F after heating at rates of 400 F per sec. Loading was programmed at a rate of 1000 psi per sec.
Pyrolytic graphite behaved in a brittle manner at all test temperatures. Average room temperature properties are: compressive strength, 13,500 psi; elastic modulus, 3.5 × 106 psi. The compressive strength decreased 6 per cent and the elastic modulus decreased 13 per cent in the range from room temperature to 3500 F. From 3500 to 5000 F a sharp decrease in compressive strength and elastic modulus occurred. Average properties at 5000 F are: compressive strength, 9700 psi; elastic modulus, 1.5 × 106 psi.
The proportional limit of pyrolytic graphite at a given temperature is approximately 25 per cent of the compressive strength. Typical stress-strain curves for specimens tested up to 5000 F are presented. Special equipment and test techniques used to obtain the required properties are described.