Mechanical and critical current characteristics of high-strength Bi 2 Sr 2 Ca 2 Cu 3 O 10 + δ multi-filamentary tapes reinforced with thicker Ni-alloy laminations with various pre-tensions

We investigated the stress-strain relation and the applied strain dependence of the critical current I c ( ϵ a p p ) of high-strength Bi₂Sr₂Ca₂Cu₃O 10 + δ (Bi2223) R&D tapes reinforced by ∼ 100 μ m thick Ni-based alloy sheets with various pre-tensions F p r e applied during the lamination process. We confirmed that the thickening of Ni-alloy laminations is useful for enhancing Young’s modulus compared with commercial tapes ( ≃ 30 μ m thick laminations). I c ( ϵ a p p ) decreases gradually and reversibly with applied strains ϵ a p p and then degrades irreversibly with larger tensile and compressive strains. The reversible strain regime tends to shift toward the tensile side with larger F p r e , indicating that application of large F p r e is effective in improving the reversible tensile strain limit. The observed I c ( ϵ a p p ) can be reproduced well by model considering ϵ a p p -linear critical current density, cross-sectional strain distribution, and Weibull-type distribution of filament damage. We clarified that different irreversible I c ( ϵ a p p ) degradations with large tensile and compressive strains can be understood by differences in the dimensions and number of cracks and ruptures (tensile strains) and bucklings (compressive strains).