Delamination analysis of high-temperature superconducting tapes based on a random defect model

Abstract

Random microscopic defects have been found in the fabrication of rare-earth-barium-copper-oxide (REBCO) high-temperature superconducting (HTS) tapes. Interlaminar failure of the tape is more likely when the interfacial bonding strength is reduced as a result of defects, which seriously jeopardizes the dependability of large magnet systems. In this paper, a three-dimensional finite element model (FEM) of the tape with random defects is developed using the Weibull distribution function to evaluate the effect of defects on the delamination of the tape. The delamination behavior under two loading scenarios were conducted (Case-I: out-of-plane tensile and Case-II: axial compression). The result show that the interfacial bonding strength is significantly affected by the defect fraction. The random characteristics of defects and their impact levels can be traced through different parameters. For case-I, the theoretical results of the effective interfacial bonding strength are in good agreement with the numerical results. During the delamination process, the occurrence of defects leads to stress oscillations in the constituent layers. Under axial compression loading (Case-II), the defect dramatically reduces the critical capacity of the tape. With increasing defect fraction, the rate of delamination propagation grows noticeably.