Discipline: Technology and Engineering
Subcategory: Materials Science
Paula-Marie Mensah - Southern University Agricultural and Mechanical College
Artificial muscles made from polyethylene copolymer and other polymers are commonly developed by researchers for testing new composite materials. Current techniques for coiling and programming these muscles are limited to producing smaller lengths of muscles in the range of 70mm to 180mm. New techniques should be investigated to increase the length of these muscles to exceed 500mm for novel applications including stitch stiffening of self-healing laminate composites. The hypothesis is that coiling the fishing line at 200 rpm under constant tension, then inserting mandrel after the fiber is coiled will result in faster fabrication. The muscle can then be heated quickly with a heat gun for 10 seconds at 95°C instead of 90 minute incubation in an oven. A 0.57mm diameter polyethylene copolymer line was cut to a length of 49 cm. Paperclips were tied at each end for attaching to the coiling apparatus. The fiber was hung vertically from a hook mounted to an electrical rotor with a fixed rotational speed. The bottom end was fixed into a static angular position but was allowed to float vertically as the muscle coiled. A mass of 360 g was also hung on the bottom of the fiber to provide constant tension throughout the coiling process. The muscle was coiled at a rate of 200 rpm in the clockwise direction and was rotated for 150 seconds until the coil began to form naturally. The coiled line was allowed to relax along its axis by allowing the tension load to spin in the opposite direction. The coil was threaded onto a .72mm steel mandrel and the coil was twisted in the clockwise direction to tighten the coil until it grips the steel mandrel without spinning. The resultant coil and mandrel combination maintain a consistent diameter of 1.98mm and is heated with a heat gun to 95°C for 10 seconds. The 2.00mm diameter coil is allowed to cool for 20 seconds before the mandrel is spun counterclockwise with a rotor out of the coil. The coil is then confirmed to be a muscle by stretching with the original load of 360g before removing the load and replacing with a 100g load for testing. The coil is heated with a heat gun and returns the 100g load to the original resting length of the coil. 100% muscle activation was achieved. The method was confirmed as effective and will be used in subsequent studies on stitched laminate composites.
Funder Acknowledgement(s): I would like to thank Dr. Ibekwe and Mark Gabriel for helping me with this research project. Funding was provided by NSF NEXTGENC3 CREST and NASA EPSCoR.
Faculty Advisor: Samuel Ibekwe,