Experimental and numerical studies on the twisted-bending mechanical performance of stacked REBCO tapes in twist stacked-tape cable

Abstract Twisted stacked-tape cable in conduit conductor (TSTC-CICC) structures are highly promising due to their ease of fabrication, flexibility, and high current density. In practical applications, the tapes within the conductor experience a combination of torsion and bending, which directly influence their mechanical integrity and electrical performance. This study investigates the mechanical behavior of stacked REBCO tapes in a 6-slot TSTC-CICC, focusing on stress and strain responses under varying twist pitches and bending radii. A shell element-based REBCO tape composite model was developed, and both experimental tests and finite element analyses were conducted to evaluate the mechanical response of the tapes under torsional and bending loads. In the experimental phase, conductor samples with twist pitches of 200 mm and 300 mm were fabricated to examine the onset of mechanical degradation under torsion-bending conditions. The sample with a 200 mm twist pitch showed critical current degradation at a bending radius of 700 mm, while the sample with a 300 mm twist pitch exhibited similar degradation at 900 mm. A finite element analysis method was developed to simulate 3D stacked REBCO tapes under torsion-bending conditions. For computational efficiency, the tapes were simplified into a shell structure. The simulation results revealed that axial strain distribution at critical current degradation points was consistent across different twist pitches and bending radii, closely aligning with experimental findings. The simulation and experimental results suggest that relative sliding between tapes plays a key role in mitigating stress concentration, potentially improving the longevity and performance of the TSTC-CICC in practical applications.