Abstract:

High-temperature superconducting (HTS) rare-earth Ba₂Cu₃O_7-x (REBCO) coated conductors (CCs) have significant potential in high-current and high-field applications. However, owing to the weak interface strength of the laminated composite REBCO CCs, the damage induced by the thermal mismatch stress under a combination of epoxy impregnation, cooling, and quenching can cause premature degradation of the critical current. In this study, a three-dimensional (3D) electromagnetic-thermal-mechanical model based on the H-formulation and cohesive zone model (CZM) is developed to study the critical current degradation characteristics in an epoxy-impregnated REBCO CC caused by the damage during a quench. The temperature variation, critical current degradation of the REBCO CC, and its degradation onset temperature calculated by the numerical model are in agreement with the experimental data taken from the literature. The delamination of the REBCO CC predicted by the numerical model is consistent with the experimental result. The numerical results also indicate that the shear stress is the main contributor to the damage propagation inside the REBCO CC. The premature degradation of the critical current during a quench is closely related to the interface shear strength inside the REBCO CC. Finally, the effects of the coefficient of thermal expansion (CTE) of the epoxy resin, thickness of the substrate, and substrate material on the critical current degradation characteristics of the epoxy-impregnated REBCO CC during a quench are also discussed. These results help us understand the relationship between the current-carrying degradation and damage in the HTS applications.

Key words: epoxy-impregnated rare-earth Ba₂Cu₃O_7-x (REBCO) coated conductor (CC), quench, damage, critical current degradation, shear stress