Widthwise Bending-Induced Response of Critical Current in REBCO Tapes

This study investigates the effect of widthwise bending on the critical current (
I
_c
) degradation of 2nd generation high-temperature superconducting (RE)Ba
₂
Cu
₃
O
_7−x
coated conductor (CC) tapes. The multi-layer stacked geometry of these tapes makes their superconducting properties highly anisotropic to stresses and strains in different directions. To apply these tapes in high-field magnets, coils, and cables, it is essential to understand their electromechanical properties, particularly the stress/strain effect on
I
_c
. In this study, limits to the allowed bending-induced deformation and strain along the widthwise direction of the CC tape before permanent
I
_c
degradation occurred were investigated. Sample holders were used to measure
I
_c
at multiple locations on CC tapes with 12 mm widths subjected to widthwise bending at 77 K and self-field. Results showed that widthwise bending can greatly influence
I
_c
degradation behaviors and cause considerable
I
_c
drops in the bent sections, particularly under tension bending. Additionally, irreversible permanent tape deformation was observed at smaller bending radii, damaging the superconducting layer under tension bending. Scanning electron microscopy observations of the (RE)Ba
₂
Cu
₃
O
_7−x
film after widthwise bending test were used to analyze the tape deformations at multiple locations and the corresponding
I
_c
degradations.