Fracturing of Solids as a Thermodynamic Process

Abstract

Instead of a number of different approaches or a formal description of experimental data, a unified approach is proposed to consider failure and deformation as thermodynamic processes. Mathematical modeling of the processes is carried out using rheological models of the material. Parametric identification of structural models is carried out using minimal necessary experiments. Based on results of these experiments, the scope of applicability conditions for this material and test modes necessary for parametric identification of models are selected. One fracture criterion is used that formally corresponds to the achievement of a threshold concentration of micro-damage in any volume of the material. Calculations of durability under conditions of varying temperature and variable loads are based on the relationship of plastic flow and failure processes distributed over the volume of the material. They are performed numerically over time steps depending on the ratio of the rate of change of temperature and stresses.

Strength Characteristics of Carbon Fiber Reinforced Plastic in Shear and Cyclic Extension-Compression after 7 Years of Climate Exposure

“…In this way, the problem of predicting the durability of a material under arbitrary changes in temperature and stress is solved. The failure time is a single characteristic of strength under all types of loading [26,33].…”

“…In case of fatigue failure of materials, it is impossible to conduct a thermal activation analysis, since local failure processes are distributed over the volume of the material. In this case, it is necessary to proceed to the mathematical modeling of the set of processes distributed in the volume of the material [33]. In this paper, only the failure processes associated with the creep of the binder are considered.…”

“…The results obtained show that the continuous presence of carbon fiber under the influence of climatic factors gives a different effect than moisture saturation-freezing, which simulates the real operating conditions of aircraft structures and reduces its strength characteristics [12,18]. But in both cases, the approach used based on the kinetic concept of fracture, considering the failure process as a set of internal thermodynamic processes, provides new information about the properties of the material [33]. This makes it possible to predict the durability of various materials under arbitrary temperature-force and temperature-time conditions.…”