Fatigue Strength of Metal / FRP Adhesive Joints Under Low Temperature

Abstract

Abstract Fiber reinforced plastics (FRP) have the excellent thermal isolation characteristics, and are used for for cryogenic structures such as super conducting magnets. Generally these FRP materials are connected with metal structures using adhesive joint, as these FRP materials loose strength by the existence of bolt holes. In this metal/FRP adhesive joints high thermal residual stresses occur under cryogenic temperatures as the thermal expansion coefficients of both materials differ large. So, improvement of strength evaluation method of these bi-material adhesive joints under low temperature become indispensable to develop high-reliability super conducting magnet systems such as form Magnetic Levitation Liner Motor Car. In this paper we present a new fatigue strength evaluation method under high thermal residual stresses using following two stress singularity parameters K and λ at bonding edges. τ ( r ) = K / rλ Heat τ(r) is stress (MPa), r is the distance (mm) from the singular point (bonding edge), K is the intensity of stress singularity and λ is the order of stress singularity. And this evaluation method is applied to Stainless-steel/Al2O3 FRP adhesive joint models.