Modeling of kinetics of curing reaction of a composite material in outer space conditions at high evaporation rates of molecules

Abstract

The paper proposes a mathematical model necessary for computational modeling of the features of the formation of mechanical properties during the transition of an epoxy resin from a viscous liquid to solid state during curing. We consider a problem in which the transition to a deformable state occurs under conditions close to those of outer space. An important role is played by the vacuum near the surface of the material and the high temperature resulting from the heating of the material under the influence of solar radiation. Computational modeling was carried out up to the moment of the transition of the medium from the state of a viscous fluid to that of a deformable body. Theoretical calculations are compared with experimental data. Within the proposed model, the formation of the material structure at the molecular level is studied and the viscosity of the medium is calculated. The material is inhomogeneous. The presence of vacuum near the boundary of the material leads to diffusion processes. The low-mass components present in the material begin to leave the material into the surrounding vacuum. The proposed model makes it possible to trace, in time and by volume of the material, the transformation of the initial low-mass components into deformable fragments formed from them and having a larger mass. The model uses parameters that have a specific physical meaning. Information about them was obtained from the analysis of available experimental data. The experiments were carried out under laboratory vacuum conditions. The temperature in the vacuum cabinet varied from 20 to 80 ℃. Numerical modeling of the technological process was carried out using the finite element method. The material was presented in the form of a semi-infinite plate. One boundary of the plate was considered to be in contact with vacuum. Through it, the low-mass components escaped into the surrounding space. The boundary conditions were derived from the assumption that the evaporation of these components only occurs when the value of the kinetic energy of diffusing molecules exceeds the amount of work necessary to overcome the energy barrier. The opposite side of the plate was considered impermeable to the material components.