Delamination Characteristics in Wide REBCO Coated Conductor Tapes Under Transverse Loading

Abstract

Superior characteristics and great potential of coated conductor (CC) tapes are some of the promises in pursuit of energy efficient application in electrical field. However, in electric device applications, the coefficient of thermal expansion (CTE) mismatch of each constituent layer, screening current, excessive radial tensile stresses during operation, and other coil fabrication related reasons might cause delamination damage in CC tapes. It was reported that the delamination among its constituent layers resulted to the degradation of its electromechanical properties on coil application. Therefore, the investigation on its delamination behavior is necessary for device application design. In this study, using the anvil test method, the delamination behaviors in 12-mm-wide Cu stabilized and brass laminated GdBa 2 Cu 3 O y CC tapes with stainless steel substrate were investigated. The mechanical delamination strength of the CC tapes for differently assembled upper anvil and CC tape configurations about widthwise direction was investigated by using a 4 mm × 8 mm size upper anvil. Mechanical delamination strength of the CC tape was not enhanced by the addition of brass laminate and showed no significant difference depending on the superconducting side or the substrate side. Furthermore, both CC tapes exhibited similar delamination mechanisms and sites but showed different fracture morphologies.

Structural Finite Element Analysis of REBCO Tape Delamination with Solid-Shell Element under Various Loads

“…Experiments measuring the transverse tensile strength have determined that the delamination usually occurs either in the REBCO layer or at the interface between the REBCO and buffer layers, but can also happen at the buffer/substrate or REBCO/silver interfaces [3]. Critical current degradation tends to occur before mechanical delamination, and does so either abruptly or gradually depending on where the delamination occurred [3,4]. The danger of delamination caused by transverse tensile stresses during thermal cooldown (particularly in epoxy-impregnated coils), thermal quenches, and Lorentz forces is well documented in literatures [5,6].…”

Review of progress in electromechanical properties of REBCO coated conductors for electric device applications

“…Recently, our groups have reported the delamination behavior in GdBCO CC tapes [64][65][66][67]. A loading fixture has been designed to achieve a good alignment during transverse tensile test as shown in Fig.…”

“…Brass lamination did not bring any enhancement of the delamination strength. Wide GdBCO CC tapes with stainless steel substrate exhibited interlaminar or mixed delamination sites [67].…”

National round robin test (RRT) for delamination strength testing YBCO HTS wires at room temperature (RT) and 77K

“…In these works, effects of the cutting edges of the CCs was found to reduce the measured values of MDS [17][18][19]. Anvil configurations [20,21], loading speeds [22] and thickness of the silver layer [23] on the MDS measurement had little influence. Since the CC delamination is intimately related to the fracture and damage of ceramic, the threeparameter Weibull distribution based on the weakest link model often provide a proper statistics analysis [24,25].…”