Fractal analysis of structural and mechanical characteristics of an interfacial region in epoxy polymer nanocomposites

It is shown on the basis of the micromechanical tensile strength model of a polymer composite, that the strength of an interfacial region material in polymer–high modulus filler nanocomposites decreases as its thickness increases, which contradicts the case of adhesion between two polymers, in which the thickness of an interfacial region is linearly dependent on the degree of interfacial adhesion. A fractal model of phase interactions is used to estimate the threshold values of the nanocluster volume ratio of an epoxy polymer matrix and the metal nanoparticles of a filler, with the mechanical stress transfer from the polymer matrix to the filler being weakened upon reaching these values. It is shown that exceeding a threshold value of the filler volume ratio violates the aggregate stability of the filler and reduces the values of the dimensionless parameter of the micromechanical model, which characterizes the degree of interfacial adhesion. With a further increase in the filler volume ratio, the values of this parameter become negative, while the composite strength virtually does not increase.