Using graphene oxide to strengthen the bond between PE fiber and matrix to improve the strain hardening behavior of SHCC

This study develops a novel graphene oxide (GO) coated polyethylene (PE) fiber (GO/PE fiber) by simply mixing PE fibers in GO aqueous solution at a certain temperature. The experimental results indicate that due to the different thermal expansion behavior, the shrinkage of GO at a higher temperature facilitates the formation of a 3D cover around the surface of PE fiber. This would increase the surface wettability, roughness and chemical reactivity of PE fiber, making it much easier for GO/PE fiber to physically and chemically interact with cement hydrates. Compared with the control strain-hardening cementitious composites (SHCC) with pristine PE fiber (2.0 vol%), the use of GO/PE fiber can improve the tensile strength and strain capacity of SHCC by 46.3% and 70.4%, without compromising the compressive strength, and the average crack opening width can be reduced from 138 μm to 58 μm. The remarkable enhancement in the mechanical properties of SHCC is due to the strengthened PE fiber/matrix bond by adding GO, which is further confirmed by results from the aligned single fiber pull out test, showing the increase of interfacial friction from 2.33 MPa to 3.99 MPa. Finally, a micromechanical model is adopted to explain the mechanism behind the improvement of the strain hardening behavior. In conclusion, the research findings provide an effective strategy to functionalize the surface properties of PE fiber by GO coating and to achieve a stronger bond at the fiber/matrix interface, leading to the development of a novel high strength SHCC with tensile strain capacity up to 6%.