Experimental Study On Delamination Strength Of REBCO Coated Conductor Tapes

REBCO high temperature superconducting(HTS)coated conductor tapes(CCs)have been widely used in many high-tech application fields due to their outstanding advantages such as high critical temperature and high critical current.Due to the brittleness of HTS materials,however,they are often made into the tape with multilayer composite structure.The thickness of each constituent layer is different and the bonding strength between adjacent layers is not uniform,which leads to delamination or even interfacial cracking.This thesis mainly studies the delamination strength of REBCO HTS CCs,and proposes a simple method for fixing,loading and testing delaminated strength of REBCO HTS CCs.A novel experimental test method for transverse tensile delamination strength and longitudinal shear delamination strength of REBCO HTS CCs is implemented by solidifying the samples of REBCO HTS CCs in epoxy resin,using 3D printing technology to process the former and fix the sample,and using the electron scanning microscope to observe the delamination characteristics.Some basic properties and experimental results related to the interface mechanics of REBCO HTS CCs are obtained.As for the transverse tensile delamination of CCs,it shows that the overall distribution of the delaminated strength is from 2.19 MPa to 2.51 MPa with the mean value of 2.34 MPa,the maximum relative error with the mean value is 9.09%,which has small dispersion.The delamination is mainly located at the interface between the REBCO superconducting layer and the buffer layer,and is less distributed inside the superconducting layer and at the interface between the REBCO superconducting layer and the silver layer.The further discussions based upon numerical calculations indicate that the tape is more likely to delaminate because of the defects,and the adhesion between the tape and epoxy resin enhances the resistance of the tape to delaminate resulting in a larger test data than real results,composite multilayer strips are sensitive to mechanical damage and defects.Therefore,errors in the sample or test method will result in the dispersion of test results.The experimental results of the shear delaminated strength of REBCO CCs show that the result ranges from 10.30 MPa to 11.98 MPa.Compared with the average value of 11.27 MPa,the maximum relative error is 8.64%.The delaminated interface is mainly inside the superconducting layer,and is less distributed at the interface between the superconducting layer and the buffer layer.This study may provide some theoretical and engineering guidance for the mechanical characterizations,basic parameters tests and delaminated failure evaluation in the applications of REBCO HTS CCs.