Fatigue Characteristics of Pressurized Artificial Muscles

Abstract

Pressurized artificial muscles show promise in both standard aircraft actuation operations and in morphing structures as an alternative to currently used actuation systems due to their high power-to-weight ratio. Pressurized artificial muscles have already demonstrated the necessary force production to be utilized as an alternative actuation mechanism. In order to better understand the feasibility of using pressurized artificial muscles as a standard actuation mechanism it is necessary to determine the life cycle of pressurized artificial muscles under high pressures, loads, and strains, and how muscle geometry and materials effect the life cycle of the artificial muscle.

This thesis presents a study to determine the fatigue characteristics of pressurized artificial muscles to address the issues noted above. The life cycle of the pressurized artificial muscle is examined at high internal pressures and high strains. The materials composing the pressurized artificial muscle, and the artificial muscle geometry are changed throughout the study to determine their effect on the life cycle of a pressurized artificial muscle. Finally a morphing aileron utilizing pressurized artificial muscles as the actuation mechanism is fatigue tested.

Fatigue testing results show that pressurized artificial muscle fatigue life is dependent on both actuator materials and geometry. Latex rubber bladders were shown to perform better than bladders of other materials. Increasing the wall thickness of the latex bladder increased the life cycle of the pressurized artificial muscles. Additionally, casting the pressurized artificial muscle in a cylindrical polyurethane resin matrix increased the life cycle of the actuator, and increasing the diameter of this resin matrix further increased the life cycle of the actuator.