Improvement Mechanism and Bending Strain Tolerance for Reinforced Bi2223 Superconducting Tapes

Comprehensive mechanical characterisation of stainless steel reinforced Bi2223 superconducting tapes was conducted using purpose built rigs. This included the effect of axial (tensile and compressive) and bending strain on the critical current (Ic) of reinforced Bi2223 tape. In addition, the axial tensile and transverse compressive stress properties of the tape were measured and evaluated. It was found that the Ic bending strain characteristic of the tape was improved as a result of sheath reinforcement, compared to an identical tape without reinforcement. A mechanism for this improvement based on the homogenising effect of the reinforcement on strain is purposed. To avoid Ic degradation, the maximum axial stress on the reinforced tape should not exceed 350 MPa, or the tensile strain should be less than 0.65 percent. Furthermore, no Ic degradation was observed for transverse compressive stresses up to 100 MPa, while an axial compressive strain of about 0.3 percent causes about 10 percent drop in the critical current.