Nonlinear mechanics of multimaterial thermoviscoelastic architected materials with snap-through instabilities

Abstract

Architected materials have unusual and interesting properties that are typically unachievable using conventional materials. Many researchers have previously focused on the design and analysis of architected materials with snap-through instabilities. This thesis aims to investigate the influence of geometric parameters, temperature and time on the snap-through buckling of one-dimensional (1D) thermoviscoelastic architected materials for applications as reconfigurable architected materials. Rigorous theoretical models of a unit cell with snap-through instabilities are first developed for both the cases of elastic and thermoviscoelastic constitutive models. These theoretical models are utilized to analyze the influence of geometric design, temperature and strain rate on the mechanics of the unit cell. With the understanding of the nonlinear mechanics of the unit cells, strategies (such as introducing small geometric variations in the unit cell design or varying the temperature) are proposed and implemented to tune the snapping sequences of architected materials made of unit cells with snap-through instabilities. With the help of the theoretical model, FEA simulations and experiments, temperature is utilized to tune the snapping sequence of these multimaterial architected materials after their fabrication. Furthermore, it is shown that a time-dependent snapping behavior can be observed in a viscoelastic architected material that has snap-through instabilities. The influence of geometric parameters and temperature on this time-dependent snapping is analyzed. The results provide fundamental understandings of interesting mechanical response that depends on time and temperature, which could help to design and develop reconfigurable and programmable architected materials with tunable properties.