Graphite-Fiber Polyimide Composites for Spherical Bearings to 340 deg C (650 deg F)
Abstract:
Journal bearings with self-alining spherical elements of graphite-fiber-reinforced - polyimide composites were tested from 24 deg to 340 deg C 75 deg to 650 deg F at unit loads up 3.5 x 10exp 7 Nsq m 5000 psi. The journal oscillated in the cylindrical bore of the composite element -15 deg at 1 hertz. Outer races and journals were metal hardened to Rockwell C-32 and finished to 10exp-7m 4 micro in. rms. A 45 wt. graphite-fiber composite gave low friction 0. 08 to 0. 13, low wear, and almost no plastic deformation under any of the test conditions. Composites with 15 and 25 wt. graphite fiber failed by plastic deformation at 315 deg C 600 deg F and 3. 5 x 10exp 7 Nsq m 5000 psi. A composite with 60 wt. graphite fiber failed by brittle fracture under the same conditions, but had very low friction coefficients 0. 0S to 0. 10 and may be a good bearing material at lighter loads.