Session: SYMP 2-1: Magneto-Responsive Materials Modeling, Optimization, and Performance

Paper Number: 139154

139154 - Characterization of Tunable Rebound Properties of Micro-Structured Magnetoactive Elastomers 

We present a novel method for controlling the rebound behavior of small mm-sized solid balls by employing magnetoactive elastomers with micro-structured surfaces.

The magnetoactive elastomer was made of a custom addition-curing polydimethylsiloxane (PDMS) matrix filled with micrometer-sized carbonyl iron particles. The samples contained 75 wt% of iron. This composite material is known to respond to an applied magnetic field with increased stiffness (magnetorheological effect) and plasticity. These two physical properties can affect the rebound behavior, but the adhesiveness of the MAE surface prevents an effective rebound.

To allow for a detachment from the surface and thus an effective rebound, the top layer of the MAE material was additionally modified by micromachining lamellar structures with different dimensions on the 100 µm scale via laser-ablation. Due to the resulting high aspect ratio, these surface structures were sensitive to the magnetic field direction.  The lamellas could stand up straight or lay down flat. These arrangements are denoted as edge-on and face-on configurations, respectively. The resulting change in the surface topography seems to be the major effect that influences the rebound behavior of the small solid balls.

The rebound behavior was evaluated by using a custom build apparatus that facilitates dropping of the balls in a precise and repeatable manner. An automated high-speed video capture enabled precise timings and reliable data that could be conveniently evaluated automatically. The balls were dropped from different heights to investigate the dependence of the rebound characteristics on the impact velocity. While falling, the balls crossed a narrow laser beam. This event triggered the capture of the video footage containing the ball impact. The video was processed using a custom software written in Python.

The vertical position of the ball over time was extracted by creating a so-called streak image from the video. An edge detection algorithm with sub-pixel resolution was employed to extract the time dependency of the vertical position of the ball. First and second derivatives were calculated numerically to obtain time dependencies of the ball velocity and acceleration. Several parameters were calculated further from these dependencies, such as the coefficient of restitution, the penetration depth, and the maximum ball deceleration. This data can be useful to evaluate energy loss, material elasticity, and surface adhesion. The experimental procedure and data processing algorithms are presented in detail. The results for the samples with different geometrical dimensions are provided as examples.

It is made evident that the magnetic field significantly influences the rebound properties of small non-magnetic balls from micro-structured MAE surfaces. The change in surface topography is an effective way to control the ball rebound. The fabrication flexibility in geometrical dimensions of surface microstructures opens a convenient way to tune the desired response to magnetic fields.

Presenting Author: Raphael Kriegl Ostbayerische Technische Hochschule Regensburg

Presenting Author Biography: Raphael Kriegl has studied Electrical Engineering and Information Technology at the OTH Regensburg in Germany and is currently a doctoral student at the same institute researching surface effects of magnetoactive elastomers under the supervision of Prof. Mikhail Shamonin.

Authors:

Raphael Kriegl
Matija Jezeršek
Gaia Kravanja
Luka Hribar
Gasper Kokot
Irena Drevenšek-Olenik
Mikhail Shamonin