Stress/strain dependence of critical current in Cu-Ag externally reinforced Ag-Zr/Bi-2212 superconducting tapes

The effects of external reinforcement on the mechanical property and the axial tensile stress/strain dependence of the critical current I_c in Bi(2212) superconducting tapes were evaluated at a temperature of 4.2 K and a magnetic field of 14 T. The monocore and 19-core superconducting tapes with three kinds of sheath - Ag, Ag-Zr and Ag-Zr/Ag double layer - were incorporated with a reinforcing Cu-Ag tape. As a result of this reinforcement, the 0.2% proof stress of superconducting tapes increased markedly without significant degradation of the I_c. The tolerance limit in strain for I_c degradation in the tapes was slightly improved and those of stress were markedly improved. The improvement in the tolerance limit in strain or stress for the degradation was more evident in the tapes with the Ag-Zr sheath, compared with those with a pure Ag sheath.