Fatigue Strength Of FRP/metal Adhesive Joints Under Low Temperature
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Fatigue strength of FRP/metal adhesive joints under low temperature T. Hattori Department of Mechanical and System Engineering, Gifu University, 1-1, Yanagido, Gifu, Japan Abstract In this paper we developed the fatigue strength and fatigue life evaluation methods of FRP/Metal adhesive joints under low temperatures. Firstly we present fatigue strength and delamination propagation rate evaluation methods using two stress singularity parameters H and λ which express stress distributions at bonding edge or delamination edges as follows. τ(r) = H/rλ Here τ(r) is stress (MPa), r is the distance (mm) from the singular point (bonding edge or delamination edge), H is the intensity of stress singularity, and λ is the order of stress singularity. Then the delamination propagation rates of the double lap joints under mechanical cyclic loadings at room temperature were measured. Using the relationship between the measured delamination propagation rates and the analyzed range of stress singularity intensity values we estimated the fatigue strength of embedded adhesive joints. We can confirm that these estimated results coincided well with the experimental results. Then we performed fatigue tests under LN2 temperatures, and we present thermal effect evaluation methods of fatigue strength and delamination propagation rate by separating the residual stress effect and pure temperature effect independently. Keywords: adhesive joints, FRP, fatigue strength, stress singularity parameters, thermal stress, delamination propagation rate. 1 Introduction Fiber reinforced plastics (FRP) have high strength, high rigidity and excellent thermal isolation characteristics so they are used for cryogenic structures such as superconducting magnets. In these cases the FRP structures are ordinary adhesively jointed with metal structures. In these FRP/Metal adhesive joints high
adhesive joints, FRP, fatigue strength, stress singularity parameters, thermal stress, delamination propagation rate.