The strain effect on critical current (Ic) in REBCO coated conductors has been intensively investigated owing to its importance for practical applications. The change in Ic with applied strain can be divided into two phenomena; namely reversible variation within elastic deformation for superconducting film, and irreversible degradation related to brittle fracture. REBCO coated conductor is the first material among various high temperature superconductors in which the non-linear reversible change in Ic with uniaxial strain is markedly observed. High stress (strain) tolerance in coated conductors is one of the advantages compared with other superconducting composites, and there are high expectations for application to high-field magnets based on such superior mechanical properties. In this review article, recent research results on the mechanical properties of REBCO coated conductors are summarized, including the stress-strain characteristic for substrate materials, the strain effect on Ic and the experimental techniques for evaluating these properties. Delamination has been recognized as one of the most critical issues for coil applications. Several evaluation methods for delamination strength and interlaminar fracture toughness were introduced.
