Nylon coil actuator operating temperature range and stiffness

Components in automotive and aerospace applications require a wide temperature range of operation. Newly

discovered thermally active Baughman muscle potentially provides affordable and viable solutions for driving

mechanical devices by heating them from room temperature, but little is known about their operation below

room temperature. We study the mechanical behavior of nylon coil actuators by testing elastic modulus and by

investigating tensile stroke as a function of temperature. Loads that range from 35 MPa to 155 MPa were

applied. For the nylon used and the coiling conditions, active thermal contraction totals 19.5 % when the

temperature is raised from -40 oC to 160 oC. The thermal contraction observed from -40 oC to 20 oC is only ~2

%, whereas between 100 and 160 oC the contraction is 10 %. A marked increase in thermal contraction is occurs

in the vicinity of the glass transition temperature (~ 45 oC). The elastic modulus drops as temperature increases,

from ~155 MPa at – 40 oC to 35 MPa at 200 oC. Interestingly the drop in active contraction with increasing load

is small and much less than might be expected given the temperature dependence of modulus.