A novel core-shell C/SiC bolt prepared by chemical vapor infiltration and its fiber strengthening mechanisms

Integrated manufacturing techniques have been extensively utilized to assemble thermal structural components made of continuous fiber reinforced silicon carbide composites (C/SiC) to fabricate large and complex components. The mechanical joint, always in terms of C/SiC bolts, become the weakest link in the components. Laminated C/SiC bolts have been invented to meet the requirements of the high temperature applications. Due to the low shear strengths of C/SiC, the threads are prone to be damaged. In order to fully employ the high tensile strength of carbon fibers, core-shell C/SiC bolt is proposed with the shell prepared by woven fiber architecture. Uniform circumferential microstructure of the threaded teeth has been obtained and the corresponding strength has been improved through fiber bridging mechanism. The results shows that the thread pull-off strength is 17.96% greater than that of the laminated thread tooth, and the stud tensile strength is slightly improved up to 2.96%. The stud shear strength is enhanced by 45.29% and 46.88% with unidirectional C/SiC rod and ZrO2 ceramic rod, respectively. The improvements are mainly caused by the fiber tension-shear coupling effects. Especially the introduction of unidirectional C/SiC rod improves the shear strength of the bolts by fully utilizing the fiber strengthening mechanisms under in-plane shear loading.