Influence of Edge Geometry on the Delamination Strength of REBCO CC Tapes Using Anvil Test Method

In wet-wound epoxy impregnated coils, the whole coated conductor (CC) tape structure experiences radial/transverse tensile stress due to large Lorentz force, which might induce delamination damage and in turn affects its transport performance during operation. The characterization of the delamination strength of CC tapes is therefore necessary for such practical applications. The anvil testing method was done to characterize the mechanical properties of REBCO CC tapes considering the possible transverse tensile stress condition in CC tape windings in coil applications. The delamination strength of three different CC tape samples slit from a 12-mm-wide one was determined using two different sized upper Cu anvils. It was observed that the slitting process has resulted to different CC tape edge geometries such as burrs and filleted corners of the substrate layer. As a result, significantly lower mechanical delamination strength was exhibited by the CC tapes when their whole width was covered by the upper anvil. Using the wide upper anvil, the edge geometry such as burrs and thick stabilizing layer played an important role on the delamination damage of the CC tape. Using a statistical method, the intrinsic strength of the CC tapes was distinguished from those that were affected by poor soldering, misalignment, and other external factors during the tests. Delamination sites mainly occurred within the REBCO film and on the buffer/REBCO interface. Finally, delamination schematics were drawn based on the delaminated CC tape's morphology.