Robust integrity of graphene in heavily stretched copper composites

The addition of graphene as a second-phase reinforcement material is expected to enhance the mechanical properties of copper (Cu) composite materials while minimizing the loss of electrical properties. However, during the processing-induced deformation of graphene/copper (Gr/Cu) composites, the interfacial couplings are commonly believed to lead to the destruction of graphene. It remains uncertain whether graphene retains its integrity and exhibits excellent performance during heavy stretching. Here, by analysing the tensile deformation behaviour of the Gr/Cu composites, we develop a “strain-slip” model and confirm that graphene initially deforms (before the critical strain of 4.0%) and then slips (beyond the critical strain) relative to the Cu substrate during stretching, thereby preserving its structural integrity. We further fabricate conductive wires using Gr/Cu composites, which exhibit a 12.9% increase in tensile strength compared to pure Cu wires, with electrical conductivity reaching 102.2% International Annealed Copper Standard (IACS) in the annealed state. Our study validates the reliability of graphene as a robust second-phase reinforcement material and provides support for the advanced deformation-sensitive applications of Gr/Cu composites.