THEORETICAL REPRESENTATIONS OF THE THERMOKINETICS OF THERMAL DESTRUCTION OF POLYMERS

A generalized theory of the thermokinetics of the process of thermal destruction of polymer materials has been developed in the context of the kinetic thermofl uctuating concept based on unifi cation of a number of independent approaches, namely, structurally kinetic (for describing elementary acts of the destruction process), mechanical (for describing the local stress at the crack tip), thermodynamic (for calculating the value of safe stress). The developed model concepts are based on experimental data relating to accumulation of disturbances in loaded samples; on force disturbances and ruptures of bonds in the vicinity of the crack tip; on submicroscopic cracks and their characteristics; fractographic investigations of the rupture face; and on the kinetic of growth of a main crack. A generalized formula of the rate of crack growth is given, the tensor of stresses at the crack tip in the conditions of mechanical and thermal loadings is calculated, the main parameters and limiting characteristics on mechanical and thermal loading of a polymer sample are calculated, a theoretical relation of the time dependence of strength in the case of a purely thermal loading in the full interval of thermal loadings from a safe to a critical one and at the stage of athermal growth of the crack has been suggested. Numerical experiments are presented.
   
Author:  É. M. Kartashov
Keywords:  time dependence of strength, longevity curve, full interval of thermal loadings; safe, critical, and limiting characteristics, parameters of the process of thermal destruction
Page:  1476