Compact actuation that is integrated into a structure's material system has the potential to provide rapid structural
reconfiguration while reducing weight. The effect of scale (diameter, overall length and segment length) on the
performance of cylindrical fiber-reinforced McKibben-like Rubber Muscle Actuators (RMA) was investigated. An
"activation" pressure was observed for all actuators at a value that depended upon the actuation construction. Upon
pressurization past the activation threshold, the overall force, stroke, and work capacity increased with increasing
actuation length and diameter. The actuation force per unit RMA cross-sectional area was predicted, and experimentally
observed, to be roughly constant after activation. By segmenting a longer actuator, a larger contraction and lower
actuation force could be achieved. Though actuation forces decreased as actuator diameter and length decreased, the
force per unit actuator volume was shown to increase with decreasing diameter including a roughly 4-fold increase in
force/volume between the 0.5" and 0.05" actuators. However, due to the small amount of total contraction for the smaller
diameter actuators, the relative work per actuation volume was decreased by roughly 35% in comparing those same
actuators. Thus, small diameter RMAs have great potential to provide needed linear actuation force within adaptive
material systems.
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