Observation on Bearing Damage Propagation of Plain Weave C/C Composites.

Bearing strength tests either with or without lateral constraint were performed for plain weave C/C composites. The tests were conducted with reference to JIS K 7080 which standardized the testing methods for bearing strength of carbon-fiber reinforced plastics. The bearing damage propagation was observed by a soft X-ray and an optical microscopy. Shear cracks were initiated and propagated rapidly at the maximum load when tests were performed without lateral constraint. Tests being performed with lateral constraint, shear cracks were initiated at the relative displacement of 4% of the pin diameter and followed by the stable crack propagation. At the maximum load the crack reached the edge of collar which constrained the specimen laterally. Then the load dropped abruptly. The loads for evaluating bearing strength which are standardized in JIS K 7080 would correspond to the shear crack initiation.