Environmental Sensitivity Tests of Graphite-Epoxy Bolt Bearing Properties

Over 200 tests were performed to study the effects of moisture and temperature on typical graphite-epoxy bolted joints. Three test specimen types were used: unnotched control laminates, filled-hole specimens containing an unloaded fastener, and bearing specimens. Five typical laminate orientations were studied. Standard 1/4-in. straight-shank fasteners were used with bolt torques varying from zero to specification values. Two types of moisture conditioning were employed: hygrothermal and conditioning with thermal spikes to 300°F superimposed on the hygrothermal background. Test temperatures were 75 and 200°F. A summary of results shows that many of the test conditions produced no significant effects. The maximum reduction from room temperature, dry performance to hot, wet performance was 18 percent.