Temperature and rate effects in damage and decohesion of biological materials

Abstract

The incredible thermo-mechanical properties of biological materials arise from the microscopic scale due to a complex hierarchical mechanism, 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 SMFS experiments and the possibility of correctly mimicking their behaviour at the lowest scales. In this thesis, different classes of models with non convex-energies 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. Moreover, within a Statistical Mechanics framework, temperature effects are considered also including the rate of loading. Different phenomena have been analyzed such as the effect of the handling device in protein unfolding, the nucleation and generation of phase interfaces in nanowires or the cooperativity of weak interactions in double stranded chains, as in the case of the DNA or the bundles of microtubules and tau proteins inside the neuronal axons. The results obtained in the thesis are compared to pieces of evidence from an extensive literature review and to the experimental behaviours of the systems described.