Numerical evaluation of the impact of introducing heterogeneous structures into the REBCO layer on fracture behavior under tensile strain

Abstract

To enhance the mechanical strength of REBCO tapes, a technique involving the creation of "heterogeneous structures" within the REBCO layer has been developed. This method entails drilling small holes in buffer layers and filling them with metal material, resulting in the formation of heterogeneous structures that effectively suppress crack propagation. What we are concerned about is the mechanism by which these heterogeneous structures affect the crack propagation subsequently impacting the mechanical performance. Therefore, by introducing the phase-field method (PFM) of fracture, we presented the propagation path of the initial crack under tension in the REBCO layer with heterogeneous structures. Additionally, we established a quantitative correlation between the fracture ratio (crack depth/tape width) and tensile strain to characterize the influence of heterogeneous structures on mechanical performance. Our findings indicated that the presence of heterogeneous structures markedly restricts crack propagation, leading to a substantial increase in the tensile strength of the REBCO tape. Furthermore, we delved into the impact of heterogeneous structure density on fracture behavior. The results revealed that higher densities of heterogeneous structures were more effective in suppressing crack propagation. Considering that the heterogeneous structure reduces the effective current-carrying area, consequently causing critical current degradation, we also explored fracture behavior under various distributions of these structures. Our results demonstrate the possibility of mitigating critical current degradation while concurrently enhancing mechanical strength by strategically adjusting the distribution of heterogeneous structures.