Delamination Properties of YBCO Tapes Under Shear Stress Along the Width Direction

In YBCO coils, the increased transport current density and magnetic field will induce larger electromagnetic force, and YBCO coated conductors (CCs) may suffer interlayer delamination by shear forces, which may give rise to performance degradation of the conductor. The delamination characteristics of YBCO CCs under shear stress should be well understood for better application of YBCO tapes to high-temperature superconducting equipment. This paper describes the experimental results for different delamination strength and critical current I-c degradation behaviors of the YBCO CCs under shear stress at the unslit edge, center, and slit edge of the conductor. The results show that the average delaminated shear strengths of 4.9, 5.9, and 3.7 MPa are recorded for the unslit edge, center, and slit edge at room temperature, whereas 6.8, 7.2, and 5.1 MPa are recorded for the unslit edge, center, and slit edge at liquid nitrogen. The different degradation behaviors of I-c under shear stress are related to the location where delamination occurs in the sample. According to the finite-element method analysis for the stress distribution of the conductor under shear stress, stress concentration leads to initial delamination of the conductor. The decrease of moment arm is suggested to reduce the effect of moment on the delamination test.