A strategy to fabricate strength-ductility enhanced braze filler reinforced by 3-dimensional graphene sponge for joining C/C composites

Abstract To address the brittle compounds formation issue in the brazed seam, an innovative 3-dimensional (3D) graphene sponge (GS) was selected to integrate with a single AgCuTi braze, forming a composite braze filler to achieve an Ag Cu eutectic dominated brazed seam with almost no brittle compounds. Interfacial microstructure of the C/C-C/C (C/C: carbon fiber reinforced carbon composites) joints brazed with and without the 3D GS reinforced braze filler were put into comparison. In particular, the braze filler/GS interface was in-depth discussed using a transmission electron microscope (TEM) combined with a high resolution transmission electron microscopy (HRTEM). Results show that a 53% increase in shear strength happened for the joints after using a 3D GS reinforced braze filler. The mechanical performance of the braze filler with and without the 3D GS reinforcement was characterized and discussed. Results show that the 3D GS reinforced braze filler is both mechanically stronger and more ductile compared with the original braze filler.