Session: VIB-13-01: Dynamics of Biological, Bio-Inspired and Biomimetic Systems

Paper Number: 118109

118109 - Effect of Waterloss on the Modal Frequencies and Damping Ratios of Clamped Hydrogel Disks 

Hydrogels have a wide range of applications in several areas like biomedical, robotics and food. Characterizing hydrogels is significantly challenging, where the mechanical properties depend on temperature, humidity and osmolarity. For instance, most common hydrogels experience continuous water loss under ambient conditions which leads to varying polymer fraction. This results in varying material properties as well as internal stresses in constrained hydrogels. Those changes in fluid phase present significant challenges with mechanical characterization. In this work, we propose a vibration-based characterization technique to tackle those challenges. We perform forced vibration tests under ambient conditions on a clamped gelatin disk. The frequencies and damping ratios of the first two axisymmetric modes are identified from the frequency sweep tests. In between vibration tests, the samples are subjected to accelerated dehydration. Samples with varying levels of water losses are re-tested and changes in the frequencies and damping ratios are recorded. We further performed supplemental experiments to monitor the changes in thickness and Young’s modulus with water loss. Through a theoretical model, we study the increasing internal stresses and Young’s modulus during dehydration and explain the dependence of modal frequencies on the water loss. The methodology can find utility in industrial settings by enabling quick, efficient, and in-situ monitoring of material properties, relaxation mechanisms and internal stresses in multiphasic soft materials via vibrations.

Presenting Author: Karthik Yerrapragada University of Wisconsin-Madison

Presenting Author Biography: Karthik Yerrapragada is a postdoctoral research associate in the Department of Mechanical Engineering at the University of Wisconsin-Madison. His research interests are in the areas of vibrations, dynamics, wave propagation and fracture mechanics of a wide range of materials like metals, hydrogels, and biological materials. He also peer-reviewed journal and conference articles in the areas of vibrations, dynamics, and controls. He received his PhD in Mechanical Engineering from University of Waterloo, Canada.

Authors:

Karthik Yerrapragada University of Wisconsin-Madison
Haocheng Yang University of Wisconsin-Madison
Melih Eriten University of Wisconsin-Madison