In-situ experimental study on the damage evolution and toughening mechanism of 3D printed YBCO superconductor impregnated with epoxy resin

Compared with YBa₂Cu₃O_7-x (YBCO) bulk fabricated by traditional methods, 3D printed YBCO superconductors have the advantages of light weight, controllable structure and short manufacturing cycle, allowing for broader promotion and use in emerging fields requiring complex geometries, such as aerospace gyroscopes. Nevertheless, the structural complexity introduced by 3D printing, combined with the inherent brittleness of YBCO ceramics, makes it challenging to clearly understand the evolution of internal damage and fracture mechanisms under stress. In this work, in-situ compression experiments were performed using micro X-ray computed tomography (μCT) to investigate the internal damage evolution of unimpregnated and epoxy-impregnated 3D printed YBCO bulk. The experimental results show that cracks in 3D printed YBCO superconducting bulk originate from pores left by ice crystals during the freeze-drying process. More importantly, the aggregated epoxy resin effectively inhibits crack propagation, a toughening mechanism found in 3D printed YBCO composite. Meanwhile, a phase-field computational model was established based on the CT characteristics, validating the experimental results and analyzing the toughening mechanism of the epoxy resin. The results indicate that adding the number, reducing the spacing, increasing the widening and raising the Young's modulus of the epoxy resin can blunt the direct extension of crack or cause crack deflection due to the redistribution of the local stress field. These findings are expected to provide new strategies for the optimized design and further toughening of 3D printed YBCO superconducting composites.