Bolt Bearing Behavior of Highly Loaded Polymer Matrix Composite Joints at Elevated Temperatures With and Without Clamp-Up

Abstract

Data are presented on time-dependent behavior of bolted joints made from 64-ply IM7 carbon fiber/K3B thermoplastic polyimide quasi-isotropic lay-up tested in pure bolt bearing and in bearing bypass. Composite panels were aged at temperatures of 177 and 204°C for 5 000 and 10 000 (h) to simulate cumulative effects of supersonic flight conditions on a bolted composite joint. Changes in joint-bearing capacity and determination of time-dependent 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°C simulated supersonic cruise temperature. Bearing creep testing revealed ripe-dependent behavior only in a very narrow loading region, above which bearing failure occurred almost instantaneously and below which no damage occurred. Testing of aged material showed degradation in material aged at 177°C for 5000 h; however, material aged at 177°C for 10 000 h demonstrated a recovery in bearing capacity, while material aged at temperatures of 177 and 204°C for 5000 and 10 000 h showed neither increased nor equivalent performance degradation. Testing with neat resin demonstrated that 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°C.