A Macro-Damaged Viscoelastoplastic Model for Thermomechanical and Rate-Dependent Behavior of Glassy Polymers

Abstract

Macromolecular Materials and Engineeringare also widely applied in medical and electronic areas. As known to all, polymethylmethacrylate (PMMA) and polycarbonate (PC), as the most representative members in glassy polymers family, generally undergo complex loading conditions when they are on practical service. Particularly, polymer materials are used to performing strong sensitivity to strain rate, temperature, and pressure. Therefore, it is necessary to conduct experiments to study the mechanical behavior of PC and PMMA under different loading modes over a wide range of temperatures and strain rates. Additionally, a thermomechanical and rate-dependent constitutive model should be proposed to catch characteristics of these kind of glassy polymers for better understanding their property for improvement their design for safer engineering application.Enormous documented efforts have been made on above investigations. On the aspects of experiment, Dar et al. [ 1 ] obtained true compressive stress-strain curves varying from 10 −3 to 10 3 s −1 and 213 to 393 K and summarized the normal trend of yield and fl ow stress and initial modulus following with the strain rate and temperature. Cao et al. [ 2 ] employed the developed split Hopkinson tension The primary objective of this paper is to develop a macro-damaged viscoelastoplastic constitutive model to describe large deformation mechanical behavior for glassy polymers at various kinds of experimental conditions. First of all, quasi-static and dynamic tension and compression tests were carried out to obtain stress-strain responses over wide range of rates and temperatures for two glassy polymeric materials, polymethylmethacrylate and polycarbonate. Then a phenomenological macroscopic damage model, covering effects of strain rates, temperatures, and effective strain, is incorporated into the constitutive model in the previous work. Furthermore, two distinct criteria are applied to predict the damage evolution affected by strain rate and temperature at elastic phase and plastic phase, respectively. The validations of the novel developed damaged model are made by the better matches with the testing data compared with the original undamaged model, and excellent agreements with the experimental result in all cases.

Cryogenic Fracture Proliferation from Boreholes under Stresses

“…From manufacturers except the surface energy [24] and fracture toughness [25]. (b) At low temperatures [26][27][28][29][30]. (c) At 20 • C and 1 atm.…”

Propagation of Cryogenic Thermal Fractures from Unconfined PMMA Boreholes

“…Table 1 summarizes the mechanical and thermal properties of PMMA at both room temperature and cryogenic temperature as it exhibits temperaturedependent properties. The compressive strength, tensile strength, and elastic modulus of PMMA increase as the temperature decreases [34][35][36]. On the other hand, thermal conductivity, specific heat, and the coefficient of thermal expansion decrease at cryogenic temperature [37,38].…”