Elimination of Necking and Aspect Ratio Dependence in Uniaxial Actuators by Continuous Fiber Reinforcement

This work presents a novel type of carbon fiber reinforcement that allows the fabrication of dielectric elastomer actuators (DEAs) whose properties are independent of their aspect ratio. The reinforcement consists of stiff carbon fibers continuously distributed in a soft matrix material. This composite layer imparts a high degree of mechanical anisotropy to the dielectric elastomer (DE), blocking deformation in fiber direction. It is shown that the reinforcement leads to a uniform strain state along the entire length of the actuator, with constant initial electroactive force and stretch dependence over several aspect ratios. This simplifies the modeling and design of strip actuators because the length of the actuator no longer affects the electromechanical properties, and there is no need to optimize fiber spacing. While the reinforcement increases the stiffness of the DEA by 30% compared to an ideal strain state of pure shear, the actuators are still able to achieve close to 8% of actuation strain under constant load. Long‐term stability evaluations have been conducted and demonstrate the reliability of the composite and its suitability for various soft robotics applications. The presented reinforcement has the potential to simplify the manufacturing of long and slender actuator geometries mimicking natural muscle.