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Characterizing the behavior of nylon actuators and exploring methods for manufacturing them to get the highest amount of output Rafie Ravandi, Ali

Abstract

Coiled nylon thermal actuators are polymer based artificial muscles introduced in 2014. Although there are many applications that can benefit from nylon actuators, there has not been much work on the methods of producing the actuators. To maximize the output of the actuators, various factors can be altered during the production phase. These factors are pre-anneal stretch, coiling tensile stress and annealing temperature. Results show that with a pre-anneal stretch of 70% and a coiling stress of 48 MPa, the highest amount of force generated can be reached without substantial failures. Also, it is found that the annealing temperature should be in the range of 170°C to 180°C. Annealing temperature needs to be in this range since the actuator should be above Brill transition temperature. Upon annealing in this temperature range, the actuator is fixed in its configuration, and it will not uncoil after it has been annealed. Additionally, the creep of the actuators and its effect on the output, has been studied. A model for the creep is proposed. The model consists of a Kelvin and a Maxwell model. The proposed model for the creep includes two damper elements, which account for the short term and long-term creep. The model fits the observed response well for the short-term creep, but for the long-term creep the goodness of fit decreases. Additionally, a model for active deformation of the actuator behavior as the result of changes in tensile stress is proposed. In particular, shape memory effects are added to account for load history dependence of the response. The active deformation model and the creep model are essential for developing a control system for using the actuators. The findings of this work can be used by researchers and device designers to bring the nylon actuators to real life applications.

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Attribution-NonCommercial-NoDerivatives 4.0 International

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