Thermal Stress and Assembling Parameters Evolution of CMC Bolted Joint under Transient Thermal Loads

Ceramic matrix composite (CMC) and superalloy bolted joints have exhibited great potential for high temperature hot structure application in hypersonic aircraft. In service conditions, the thermal expansion mismatch between CMC and superalloy plates will cause complex thermal stress and strain distributions at hole-edge areas and assembly parameters changes of the joints under elevated temperatures. These effects might lead to early damage of joint structure, which will endanger the structural integrity and load carrying capacity of aircraft components. In the present study, transient heat transfer and thermo-structural analysis of C/SiC composite and superalloy bolted joint were carried out by using a commercial FEA software ABAQUS. The stress distributions at hole-edge areas, pre-load loosening, and variation of bolt-hole clearance of CMC bolted joints under transient temperature rises were discussed for better understanding of high temperature structural behaviors. Results showed that pre-load declined with the increase of imposed hot side temperature, due to the thermal expansion mismatch between CMC and superalloy. The bolt-hole clearance for the composite plate decreased, whereas the clearance for the superalloy plate increased with the rise of temperature.