Tensile fatigue properties of composite/metal bolted joints with 3-pin and sleeves

Abstract

Countersunk bolt joints with sleeves have been used in composite connection structures, and their fatigue performances need to be studied. Based on the experimental investigation conducted on the single lap CFRP/titanium alloy bolted joint with 3-countersunk head bolt and sleeves, the fatigue models of composite laminates and metal structures were established to analyze the fatigue performances of the structure, and finite element analysis on joints without sleeves was also carried out to study the influences of the sleeves on fatigue performance of the joint. The results show that the use of sleeves can more effectively improve the fatigue performance of the joint compared to that only using interference fit. The fatigue life of laminate is increased by about 3.6 times, the titanium alloy plate increased by about 2.7 times, and the bolts are increased by about 14 times. Only the titanium alloy plate of the joint fails, but not the fastener. Combined with analysis on the experimental results, it is found that the fatigue failure mode of bolted joints structure will change with different load levels due to the different fatigue properties between composite materials and metal materials; and the metal structure is prone to be damaged under a certain load level.

Keywords

• composite/metal joint
• bolted joint
• countersunk bolt with sleeve
• tensile fatigue perfor-mance
• progressive damage model