Study On The Life Prediction Of Composite-to-Titanium Bolted Joints

Composite materials have been widely used in aeronautic structures dueto their high specific intensity, high specific rigidity, excellentcorrosion-resistance and excellent designability. Composite bolted joints arethe most commonly used composite joining, because they can transmit highload. In order to reduce the structure weight of aircrafts, the allowable designstrength values become higher and higher, that makes the fatigue problem ofcomposite materials reveals. Consequently, the life prediction ofcomposite-to-titanium bolted joints is an important research project.A progressive damage method of predicting the fatigue life ofcomposite-to-titanium bolted joints is established in this paper, which is basedon the theory of unidirectional ply. The three-dimensional model is built inABAQUS and the stress analysis is submitted. The residual strengthdegradation model based on the degradation of stiffness of the compositelamina subjected to fatigue loadings are deduced and established by couplingthe normalized fatigue life method. The three-dimensional Hashin-Yeh failurecriteria are introduced into the method to detect damage for diverse damagemodes.An experimental study on fatigue performance of composite-to-titaniumbolted joints was performed. The fatigue life, hole elongation and failuremode are detected to analysis the fatigue performance of the structure. Finally,the fatigue life of composite-to-titanium bolted joints in two-stagetension-tension fatigue loading conditions are predicted by using fatigueprogressive damage method established in the paper and the influence ofdifferent bolt-hole clearances over the fatigue life of bolted joints is analyzed by simulation.