Phenomenological Kinetic Equation of the Conversion for a Binder of Composite Materials Based on Isothermal Tests

Abstract

In the problems of technological mechanics: the manufacture of structures from composites, packaging and deployment of products from prepreg for space purposes, and others, it becomes necessary to calculate the current mechanical properties of a composite material with an incompletely cured binder. Such properties are determined primarily by the binder state, which may be described by the conversion kinetic equation. The parameters of the kinetic equation depend on many factors: temperature, diffusion, the presence of a catalytic system, modifiers, reagents, the formation of by-products of kinetic reactions, the evaporation of reagents, the effect of radiation, etc. Reliable consideration of the influence of each factor in the kinetic equation turns out to be practically impossible. Therefore, most authors use the phenomenological conversion equation based on experimental data, since these data reflect all the features of the kinetic process. We consider the first order conversion equation, which takes into account auto-acceleration and auto-deceleration. The equation parameters are determined on the basis of isothermal experimental data by the following method. The equation for the conversion rate is integrated, the integral is used to construct a system of equations containing experimental data and the desired approximation parameters, which are determined by standard mathematical methods. The dependence of the kinetic equation parameters on temperature is also constructed by approximation. Examples of constructing conversion equations for a two-component and industrial multicomponent Barnes mixture are given. It is shown that the parameters of the kinetic equation in both cases significantly depend on temperature, and for a multicomponent mixture this dependence is more complicated due to the simultaneous implementation of several reactions. Examples of using the obtained kinetic equation to calculate the curing degree of samples under a given temperature loading are given.