Mathematical modeling of thermodynamic processes of failure and deformation of materials

The results of testing of carbon fiber specimens under monotonous loading with different rates and under variable loads of various types are analyzed. The analysis is carried out on the basis of a thermodynamic approach both in the case of general material flow (creep) and in the case of local flow processes in materials associated with fatigue failure. The failure and deformation of the material under variable loads, causing both of these processes simultaneously, is described by mathematical models linking plastic strains with the accumulation of damage in it. Since the fracture of carbon fiber under the predominance of compressive loads is similar to the fracture of metal alloys under tensile loads, the same methodology for predicting its durability is used. Thermal activation analysis of experimental data and mathematical modeling of internal processes in the material reveal the cause of failure in each case of variable loading, depending on the level of mean stresses, process dispersion and temperature.