CYCLIC ACTUATOR BEHAVIOR OF FERROGELS

摘要

Ferrogels are low modulus polymer materials with embedded magnetic powder filler giving them the capability to strain in a magnetic field. The large strains, high energy densities, and fast response that have been reported make these materials attractive for actuator applications, however, a full understanding of the dynamic behavior is lacking. In this work the following behaviors are characterized: (1) the effect of gravity is determined by comparing behavior in two configurations, (2) the effect of compositions is investigated for 9 samples of different matrix and filler compositions, (3) the effect of frequency is determined for sinusoidal inputs between 0.1 and 80 Hz and, (4) the instantaneous and long-term strain behavior is discussed based on the ferrogel response to step inputs of magnitudes up to 2200 Gauss. It was found that the highest strains are achieved for the most flexible samples with the highest amount of magnetic filler tested in a configuration in which gravity acts in opposition to the magnetic attraction. Lower frequencies allow for larger strains because more time is allowed for visco-elastic motion. Finally, the step response shows that the strain occurs in two types. First, is an instantaneous strain; second, is a visco-elastic deformation that takes place over an extended period of time.