A leakage rate prediction method of wet-assembly hybrid bonded/bolted joints based on porous media theory available for different environment conditions

The wet-assembly hybrid bonded/bolted (WHBB) joint is increasingly employed in aircraft fuel tank structures owing to its advantageous mechanical strength and sealing performance. However, the integral tank is susceptible to leakage during service, particularly at the joint, which seriously endangers the flight safety of the aircraft. In this paper, a leakage prediction method of WHBB joint based on porous media theory is proposed, in which the shape and characteristic length of the sealant layer are taken into consideration. The model parameters are determined by the analysis and treatment of the defect state of the WHBB joint section. The prediction results agree well with the experimental data, which were acquired by self-designed sealing leakage rate measurement system, and the deviation between the predicted results and the average value of the experimental data is less than 20%. Furthermore, in order to verify the environmental adaptability, the prediction results based on 2D cutting sections of the joints and experimental results under three different loading conditions are compared. The comparison results not only prove the accuracy of the prediction model, but also reveal the important influence of tensile fatigue load on the sealing performance of the structure. The tensile fatigue loads lead to two orders of magnitude increase in leakage rate, and the reason is that the repeated stretching and compression process lead to an increase in interfacial cracks between the adhesive layer and the hole wall, thereby accentuating the defects within the adhesive layer.