TEMPERATURE AND RATE EFFECTS IN DAMAGE AND DECOHESION OF BIOLOGICAL MATERIALS

作     者：Bellino, Luca 

作者机构：XXXIV PH.D. Program in Mechanical and Management Engineering India MAT/07 - Mathematical Physics Italy 

出 版 物：《arXiv》 (arXiv)

年 卷 期：2022年

核心收录：

主　　题：Statistical mechanics 

摘      要：The incredible thermo-mechanical properties of biological materials arise from the microscopic scale due to a complex hierarchical mechanism, which is regulated by microinstabilities at the molecular level. The description of such complex structures is allowed by both the know-how introduced by the advent of single molecule force spectroscopy experiments, which gives the possibility of studying such systems in different thermal and mechanical conditions, and the possibility of correctly mimicking their behaviour at the lowest scale by introducing mathematical models based on non-convex energies. In this thesis, different classes of models are introduced to describe the important features of phase transition, decohesion and damage under different conditions of applied forces and displacement, thermal fields and rates of loading. By increasing the level of complexity of such models, different phenomena have been analyzed. For instance, by introducing a chain of bistable units to mimic the behaviour of a titin molecule undergoing unfolding, it has been described the effect of the handling device in single molecule experiments, which strongly affects the system’s mechanical response, leading to large errors in the measure of the resulting force or displacement. Temperature effects are considered within a Statistical Mechanics framework, also in the case when non local interactions are introduced. Indeed, phenomena such as the presence of a stress peak in the force-extension diagram and corresponding to the generation and nucleation of a phase is experimentally observed in tensile tests on memory shape nanowires or polymer materials and can be described as a competition between interfacial energy terms and entropic effects. The cooperativity of weak interactions, such as hydrogen bonds, has been also studied to highlight phenomena such as decohesion and fracture in biological systems. Indeed, simple amino acids are arranged in a multiscale fashion resulting in high perfo