Effect of fit conditions on mechanical properties of C/SiC online riveting unit

According to the on-line rivet connection forms widely used in chemical vapor infiltration (CVI) process 2D-C/SiC thermal structures and characteristics shown in ground tests, the effects of different forms of clearance or interference fit between rivets and flat openings on mechanical properties were studied. A typical test piece with rivets was prepared and the microscopic morphology was observed. Through rivet push-out test, the push-out static strength and fatigue rules under different matching conditions were obtained. By comparing the tensile static strength of the specimens with rivets and the specimens with holes under different matching conditions, the rule of in-plane strength performance degradation caused by C/SiC online riveting was obtained. The characteristics of fiber bundle deformation, hole edge pre-stress and local area damage of materials were analyzed, and numerical modeling calculation was carried out according to morphology observation. Then, an improved point stress failure criterion (PSC) considering the effect of stress concentration at the hole edge was proposed for C/SiC interference fit riveting. Research shows that interference fit can improve the connection reliability between rivet and hole, significantly improve the push-out static strength and fatigue strength of rivet. But the interference fit riveting process makes the local carbon fiber at the hole edge extrude and deform, which leads to the prestress at the hole edge.