The comprehensive experimental investigation of tensile strength and sealing performance for wet-assembly hybrid bonded-bolted (WHBB) joint with different bolt-hole clearance

Wet-assembly hybrid bonded/bolted (WHBB) joint is a kind of sealing fastener that contains sealant both in bolt-hole clearance and between CFRP laminates, which is increasingly applied in composite aircraft fuel tanks. As the guarantee of tensile strength and sealing performance, the thickness and interface characteristics of bolt-hole sealant layer are investigated by a newly developed comprehensive evaluation method in this paper. The results indicate that the tensile strength of WHBB joint is positively correlated with the bolt-hole clearance. As for the sealing property of WHBB joints, the leakage rates of WHBB joints with bolt-hole adhesive layer (0.01, 0.03 and 0.05 mm) is three orders of magnitude less than that of joints with 0 mm adhesive layer. Moreover, the rising slope of leakage rates of the WHBB joints decreases with the increase of bolt-hole clearance under tensile fatigue loads, which means the WHBB joint with higher bolt-hole clearance shows better tensile fatigue resistance. The micro-morphology of bolt-hole interface indicates that the sealing property of WHBB joints is increased significantly due to the effectively enhanced interface behavior.