Mechanical properties of pyrolytic graphite

A series of mechanical strength and thermal expansion tests was carried out from room temperature to 5000 F on the two microstructural types of current production pyrolytic graphite. Results indicate that with appropriate precautions in selecting test material, machining and testing specimens, current production pyrolytic graphites yield higher, more reliable mechanical property values. The contribution of process improvements to this increase cannot be specifically separated although it may show up principally in allowing more of a given batch of material to be selected. The present series of tests shows pyrolytic graphite to have an ultimate 'a' direction tensile strength of 18,000 = 2,000 psi at room temperature rather than previously found values of 11,000 = 5,000 psi. The largest difference between surface nucleated and continuously nucleated material was obtained in torsional tests parallel to the planes; values of 1555 = 60 and 2880 = 265 psi were obtained respectively throughout the temperature range to 5000 F.