High-temperature effect on the mechanical performance of screwed CFRPI–TC4 alloy joints repaired with metal inserts

Abstract

This paper seeks to study high-temperature effect on mechanical performance of screwed single-lap carbon fiber-reinforced polyimide–TC4 titanium alloy joints repaired with metal inserts. Quasi-static tension tests were conducted at room temperature (RT) and 250℃ to determine the joint strength and stiffness of repaired joints with metal inserts. Based on the experimental results, high-temperature effect on joint strength and stiffness and insert repair efficiency were analyzed and discussed. A new analytical model was established to evaluate the effect of high temperature on joint stiffness. It is concluded that (1) joint strength and stiffness for all configurations are lower at 250℃ than that at RT, showing the expected detrimental effect of high temperature on joint strength and stiffness. The reductions in joint strength and stiffness depend on the joint configuration; (2) the repair efficiencies of embedded conical nut for joint strengths of protruding and countersunk head screw joints decrease, but those for joint stiffness increase at 250℃ as against at RT. Unlike the repair efficiencies of embedded conical nut, the repair efficiency of bushing for joint strength is slightly greater, but that for joint stiffness is less at 250℃ than at RT; and (3) the developed analytical model is capable of predicting the displacement of screwed single-lap carbon fiber-reinforced polyimide–TC4 joints at RT and high temperature, and there is good agreement between the experimental data and the predicted curves.

Progressive damage characteristics of screwed single-lap CFRPI-metal joint subjected to tensile loading at RT and 350°C

“…This is in accordance with findings in literatures. 2,5,6 Significant results that emerged from Figure 3 are summarized as follows: (i) in no-slip stage, load transfer between jointed plates takes place due to static friction, resulting in elastic deformation of plates; (ii) in slip stage, the existence of relative slip between plates increases an additional displacement, causing a near-zero joint stiffness; (iii) in linear stiffness stage from about 0.25 kN, the interface between the screw and fastener hole becomes in full-contact, leading to the load transfer between plates to induce the bearing force between the screw and fastener hole; (iv) in slower rising stage, obvious bearing damage initiates around the hole, and then propagates with the increase in the external load, activating a progressive reduction in joint strength and stiffness; (v) in final failure stage, bearing failure on composite plate emerges, and thus the load capacity of the joint declines.…”

“…A major issue with the current screwed CFRPI-metal joints is the vulnerability to the shear loads, that is, the interaction between screw threads and hole walls of composite members usually cause an intense thread embedment. [3][4][5][6] Therefore, mechanical characteristics and failure mechanism of screwed CFRPI-metal joints are crucial in the design and repair of aero-engine structures.…”

Mechanical performance of adhesively bonded carbon fiber reinforced boron‐modified phenolic resin plastic‐titanium single‐lap joints at high temperature

“…Titanium alloys have been widely used in the manufacturing of structural components for high-speed aircraft, rockets, and missiles due to the excellent mechanical properties and heat resistance. 32,33 The mechanical properties of TC4 titanium alloy at different temperatures are shown in Table 3. 34…”