Multilayer modeling framework for analyzing thermo-mechanical properties and responses of twisted and coiled polymer actuators

Abstract The twisted and coiled polymer actuator (TCPA) has a complex multi-scale structure consisting of crystalline micro-fibrils and an amorphous matrix at the micro-scale, which are organized into a macro-scale fiber. When the polymer fiber undergoes twisting and coiling, its mechanical and thermal properties become variable. In this study, we developed a multi-layer modeling framework capable of accurately predicting the effective mechanical and thermal properties, as well as the thermo-mechanical responses of the TCPA. Our numerical results demonstrate that the effective mechanical and thermal properties of the TCPA are influenced by the radius and twisting angle of the polymer fiber. By analyzing the precise mechanical and thermal properties, the numerical calculated driving responses exhibit good agreement with experimental data. We also examined the influence of initial helical radius, helical pitch and fiber radius on the driving responses of the TCPA. The proposed numerical model can be further utilized to optimize the driving responses of the TCPA by adjusting geometric parameters and the twisting angle of the polymer fiber.