Mechanical Analysis of Thermally Activated Muscle-Like Actuator Made of Twisted and Coiled Fishing Line

In this study, 8 samples of thermally activated muscle-like actuators were designed and fabricated by twisting and coiling fishing lines made from nylon threads with diameters of 0.5 and 0.8 mm. In the first step, the empirical relation of the actuators final length with their initial yarn length was investigated. Then, to release the residual stresses stored during the twisting procedure, the twisted and coiled actuators were annealed at 120°C for 3 hours. Then the mechanical behavior of prepared actuators was studied via a tensile test. Results showed the stiffness of 41.74468 and 163.73126 (N/m) for yarns with diameters of 0.5 mm and 0.8 mm respectively. The thermomechanical behavior of the actuators was also investigated with hot water at 40, 50, 60, 70, and 80°C. A roughly linear relation with R2 of 0.9878 was found between strain rate percentage and test temperature for the actuator with the diameter of 0.5 and a roughly linear relation with R2 of 0.99 was found between strain rate percentage and test temperature for the actuator with the diameter of 0.8 mm while the actuators were stretched with a load with a weight of 0.145 kg and the maximum strain rate percentage were 2.0253 and 6.1403 at 80°C for actuators with diameters of 0.5 and 0.8 mm respectively.