Numerical Assessment of Tilted-Helical Fiber Orientation Effects on Deformation of Pneumatic Soft Actuators

Pneumatic stimulation is one of the popular types of actuations in the field of soft actuators, especially in fiber-reinforced pneumatic actuators, which could have many applications by producing different deformations such as lengthening, expansion, twisting, and bending. Fiber-reinforced tubes have been extensively studied, especially those reinforced by regular helical fibers. In this regard, several sets of fibers are needed to obtain more complex deformations such as coiling, a combination of bending, and twisting. However, an alternative fiber orientation could generate coiling with only one fiber known as the tilted helical orientation. This orientation has an extra parameter called tilt angle. Thus, this work intends to investigate the effect of tilted helical fiber orientation on the coiling behavior of the fiber-reinforced pneumatic actuator. For this purpose, through numerical analysis based on finite element simulation, the effects of pitch and tilt angle of the fiber orientation on the twist and curvature of the actuator’s deformation are studied. In addition to the numerical approach, four prototypes are fabricated and experimental data is used to evaluate the simulation results. The results obtained from the simulation are used during a series of post-simulation calculations to extract the curvature and twist. Different fiber orientations are simulated in a comprehensive range of different tilt angles and pitch values. Results are presented in several plots to demonstrate the fiber orientation effects. Next, these diagrams are summarized in two contours. Contour diagrams could be used as a map to predict the coiling behavior based on the fiber orientation parameters. Finally, by presenting a preliminary inversed design chart, a relationship between desired deformation and fiber orientation is developed based on spatial surface fitting. These results took an initial step for the design of tilted-helical fiber-reinforced actuators, with potential application to a wider class of inflatable soft actuators to program a desired coiled configuration through integrating a single tilted-helical fiber. Additionally, as a supplementary study, this work has included an appendix to demonstrate other potential applications of the numerical simulations through the introduction of a novel sunlight-driven material. Finite Element Method (FEM) analysis is employed to evaluate and explore the potential for developing actuators utilizing this innovative material.