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Analytical Modeling for Stress Distribution around Composite Interference Fit Joints with Elastic Pins

TAO WU, KAIFU ZHANG, HUI CHENG, PING LIU, YI LIANG and YUAN LI

Abstract


Interference fit joints can bring benefits for composite structures such as fatigue life improvement. In these structures, as fasteners are oversized, plates have already deformed before loading, and residual stress exists around holes. As a result of composite anisotropic property and contact relationships between fasteners and plates, the residual stress is uneven around the hole and depends on several factors. All of these make the problem quiet complex, and bring difficulties in estimating the loading situation of joints. An analytical method considering pin elastic deformation was proposed to analyze the residual stress around composite interference fit joints in this paper. The method was based on the Lekhnitskii complex variable approach. Stress functions which satisfied the load condition of interference fit pinned plates were built. Unknown coefficients in stress functions were determined according to displacement boundary expressions. By this method, stress components could be obtained if elastic constants and interference value were known. 3D finite element models were built to verify the validity of the analytical method, and results were in good agreement. The effects of material properties and interference value were discussed: (1) Material properties had obvious effects on stress distribution. Radial and circumferential stress distributed like circle on quasi isotropic plates, while like figure eight on zero dominated plates. Rigid pins obtained apparently higher stress level than elastic pins; (2) Larger interference value led to higher stress level. But the shape of stress curve would not change when interference value varied.

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