Bolt bearing fatigue of polymer matrix composites at elevated temperature

Polymer matrix composites (PMCs) are being considered for a number of elevated temperature (177°C/350°F) aerospace applications. Mechanical fasteners may be required to join these PMCs, making the elevated fatigue behavior of these highly loaded joints a possible design concern. A modified test set-up was used to simulate the stress state of a bolted composite joint. Using this modified set-up, IM7/PETI-5 showed a 20% improvement over IM7/K3B in elevated temperature bearing fatigue tests. Furthermore, the bearing fatigue life of IM7/PETI-5 showed no dependence on frequency or 10,000 hours thermal aging. Upon completion of the fatigue testing, failure analysis revealed that the bearing failure mechanisms were delamination, ply buckling, and 0°-ply fracture. Overall, IM7/PETI-5 was found to be very durable with no significant time dependant behavior at 177°C (350°F).