Study on the Residual Stress Relieving Mechanism of C/C Composite-Nb Brazed Joint by Employing a Structurally Optimized Graphene Reinforced Cu Foam Interlayer

• Main Authors: Hongliang Li, Zeyu Wang, Hassaan Ahmad Butt, Maocheng Ye, Hao Chen, Tianmo Zhao, Manni Li, Qiang Ma, Yucheng Lei
• Format: Article
• Language: English
• Published: Frontiers Media S.A. 2021-09-01
• Series: Frontiers in Materials
• Subjects: Cu foam; interlayer; residual stress; C/C composite; brazing; structurally intact
• Online Access: https://www.frontiersin.org/articles/10.3389/fmats.2021.761088/full

Cu foam has previously been investigated and verified to be an excellent interlayer candidate for relieving high residual stress within C/C composite-Nb brazed joints. However, the optimized geometric structure of Cu foam for brazing has never been properly investigated since it was always employed as a reactant for acquiring homogeneous distribution of the interfacial structures in the brazed joints. In this work, graphene reinforced Cu foam composite (G-Cuf) interlayers were used for brazing C/C composite and Nb. Through the protection effect of graphene on the Cu foam substrate, the impact of porosity and thickness of a structurally intact Cu foam on the joint structure and properties were investigated by finite elemental analysis as well as through experimental studies. By introducing a G-Cuf interlayer with an optimized porosity of 90% and thickness of 0.15 mm, the shear strength of the C/C composite-Nb brazed joint reached 45 MPa, which is 3.5 times higher than that of the joint brazed directly without an interlayer. The strain energy of the brazed joint assisted by G-Cuf interlayer reduced from as high as 10.98 × 10–6 J to 6.90 × 10–6 J, suggesting that the residual stress was effectively mitigated.