Innovative Fatigue Method in Single-Lapped Mixed Composite Joints

Abstract

The aim of the work is to systematically investigate the mechanical properties of single-lapped mixed, i.e., bolted and bonded and riveted and bonded, composite joints subjected to tension-tension (T-T) cyclic loading by using the new model grips in comparison with that by conventional MTS grips. A system of devices to measure clamping force is disclosed. The U.S. patent new model grips are introduced and manufactured to conduct cyclic tests and generate empirical results, highlighted as follows. Through the parametric study we find that the obtained fatigue strength and life of the mixed joint by MTS grips are larger than that by new model grips, i.e., the real values are over-estimated by MTS grips. Our data by new model grips are correct. The bolted and bonded joint is found stronger than the riveted and bonded joint mainly attributed to the features of respective mechanical fastening. The mixed joint of cross-ply adherend is more resistant to cyclic loading than that of quasi-isotropic adherend. Additionally, the overlap length and clamping force are two dominant factors in fatigue strength and life. The increase in overlap length of a mixed joint will increase the fatigue strength and life until an asymptotical value is approached. Similarly, the increase of clamping force will result in a rigid joint to possess more resistance to cyclic loading.

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