Nonequilibrium Statistical Theory Of Damage And Fracture For Glassy Polymer

The damage and fracture of glassy polymer is a complex multi-scale and multi-stage process. It starts from the failure of molecular chain entangled network on microscale, which arouse nucleation, growth and rupture of craze on mesoscale and further initiate the formation and propagation of microcracks, finally generating a major crack and then leading to macro-fracture of material. The fracture of material is a dynamic process which has a strong dependence on defect distribution in material and evolves with time in a manner of high nonlinearity. To understand the whole process comprehensively, one needs to know not only the mechanism of damage and fracture occurred in material on microstructure and mesostructure level but also their kinetics. These are the main tasks of polymer physics and material science, respectively. On the other hand, from macroscopic point of view material could be considered as a continuum. One investigates the mechanic response of materials under outside excitement, and then construct a frame to describe it phenomenologically with Mathematics. Continuum Mechanics has already gained a great deal success in this field. Furthermore, it is the work of Statistical Physics to form a link among microscale, mesoscale and macroscale of material structure and puts up a bridge across the discipline of Polymer Physics, Material Science and Continuum Mechanics. It is also one of the most important pillar to mold a new borderline subject, that is, Polymer Mesodamage Statistical Mechanics.Until now, in the field of Polymer Material Science, people have done many research works on mechanism and dynamics of craze nucleation, growth and rupture. Although some useful clues have been uncovered, it still confines in the observation and induction for the damage and fracture behavior of materials on mesoscale. Moreover, it stays in a stage of qualitatively explaining material macromechanical properties based on the knowledge of local micro- or meso- damage and fracture in materials. However, in the frame of Continuum Mechanics material macromechanical properties can be quantitatively described in principle. Because it is too general to have any micro- or meso-physical meaning, we can hardly see the feature of damage and fracture in different materials as well as the relationship between them and mesostruture and mechanism of meso- damage and fracture of material. Therefore, it is imperative to induce numerous achievements in scientific research on the mechanism of damage in polymer, from which to abstract dynamically physical model of mesodamage in polymer. From this model, the mesodamage statistical constitute equation and the statistical distribution of fracture strength could be derived by means of Nonequilibrium Statistic Physics. Thus the purpose of this dissertation is to establish a new Nonequilibrium Statistical Theory of Damage and Fracture for Glassy Polymers to reveal the physical nature of microdamage in macro-damaged polymer, to form a link between micro- and macro- mechanical properties of materials, and to give a micro-physical meaning of macro-mechanical properties.The dissertation could be divided into six chapters:First of all, an extensive review has been given in chapter 1 on the topic "Statistical Mechanics of Meso- Damage and Fracture for Glassy Polymers". This chapter comprehensively describes recent developments on criteria, mechanism, kinetics and statistical model for nucleation, growth and rupture of craze in glassy polymers. Then we have briefly discussed mesodamage statistical description recently developed from the field of metal materials. At the end of chapter 1 we propose our views on the current state about the field of polymer meso- damage and fracture, and then point out the direction of further research.