Bolt bearing behavior of highly loaded polymer matrix composite joints at elevated temperatures with and without clamp-up

Data are presented on time-dependent behavior of bolted joints made from 64 -ply IM7 carbon fiber/K3B thermoplastic polyimide quasi-isotropic lay-up te sted in pure bolt bearing and in bearing bypass. Composite panels were aged at temperatures of 177 and 204 degrees C for 5000 and 10000 (h) to simulat e cumulative effects of supersonic flight conditions on a bolted composite joint. Changes in joint-bearing capacity and determination of time-dependen t behavior have been covered in this study. Test coupons sized and drilled to correspond to the ratios found in actual joints were loaded over a wide range at both with and without clamp-up forces. Testing at 177 degrees C si mulated supersonic cruise temperature. Bearing creep testing revealed time- dependent behavior only in a very narrow loading region, above which bearin g failure occurred almost instantaneously and below which no damage occurre d. Testing of aged material showed degradation in material aged at 177 degr ees C for 5000 h; however, material aged at 177 degrees C for 10000 h demon strated a recovery in bearing capacity, while material aged at temperatures of 177 and 204 degrees C for 5000 and 10000 h showed neither increased nor equivalent performance degradation. Testing with neat resin demonstrated t hat the matrix material becomes more brittle both with temperature and with aging. It was concluded that this material experiences no significant time -dependent deformation for temperatures at or below 204 degrees C.