A characteristic curve-based numerical framework for predicting strength of multi-bolted composite joints subjected to hygrothermal condition

Many works have been made for predicting the failure of composite joints. However, there is still lack of method for multi-bolted composite joints subjected to the hygrothermal environment. In this work, a characteristic curve-based numerical framework is proposed, which includes two main steps and shows low computational cost. Firstly, a 3D finite element model considering hygrothermal effects is established to analyze the bolt-load distribution of multi-bolted joints. Secondly, a new characteristic curve considering the hygrothermal influence is used to obtain the failure pattern and strength of composite joints. The two-, three- and four-bolted composite joints with –55 ℃/dry (CTD), 23 ℃/dry (RTD) and 70 ℃/wet (ETW) conditions are investigated. The test outcomes present good agreement with predicted results, which illustrates the effectiveness and applicability of the proposed method. Meanwhile, it is shown that the environmental condition affects the bolt-load ratio slightly, but does not change the location of the key loaded hole. Furthermore, deviations of the strengths in CTD and ETW conditions are about 5% and –16% from that in the RTD condition, respectively. The environmental condition does not affect the failure modes of two- and three-bolted joints, whereas changes the failure mode of the four-bolted joint. The proposed method is efficient, reliable and needs only linear elastic FE analysis, making it applicable for engineering practice.