Effect of Nanoparticles and Their Anisometry on Adhesion and Strength in Hybrid Carbon-Fiber-Reinforced Epoxy Nanocomposites

Abstract

Carbon-fiber-reinforced plastics are composite materials with record-high specific strength, which depends on the efficiency of stress redistribution between the reinforcing fibers by the polymer matrix. The problem is the accurate assessment of adhesion in the carbon fiber–polymer matrix system since it affects the overall strength of the composite. This paper provides a novel electrochemical method for determining adhesion by estimating the critical length of carbon fibers that protrude above the fracture surface of the fiber-reinforced composite using their electrical conductivity and insulating properties of the polymer matrix. The method has been successfully applied to evaluate adhesion in carbon plastics having an epoxy matrix filled with nanoparticles of different anisometry: carbon nanotubes, organomodified montmorillonite, or detonation nanodiamonds. In addition to adhesion measurements, the effect of nanoparticles on the viscosity of epoxy binder, its impregnation efficiency of carbon fibers, curing, glass transition, and tensile strength of fiber-reinforced composites was estimated. Nanodiamonds at a mass fraction of 0.1% proved to be the most effective for improving the quality of epoxy carbon plastics, increasing fiber–matrix adhesion by 2.5 times, tensile strength by 17%, and not decreasing the glass transition temperature.