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Published July 2022 | public
Journal Article

Particle-Assisted Laser-Induced Inertial Cavitation for High Strain-Rate Soft Material Characterization

  • 1. ROR icon California Institute of Technology

Abstract

Background

While there are few reliable techniques for characterizing highly compliant and viscoelastic materials under large deformations, laser-induced Inertial Microcavitaton Rheometry (IMR) was recently developed to fill this void and to characterize soft materials at high to ultra-high strain rates (O(10³)∼O(10⁸) s⁻¹). Yet, one of the current limitations in IMR has been the dependence of the cavitation nucleation physics on the intrinsic material properties often generating extreme deformation levels and thus complicating material characterization procedures.

Objective

The objective of this study was to develop an experimental approach for modulating laser-induced cavitation (LIC) bubble amplitudes and their resulting maximum material deformations. Lowering the material stretch ratios during inertial cavitation will provide an experimental platform of broad applicability to a large class of polymeric materials and environmental conditions.

Methods

Experimental methods include using three types of micron-sized nucleation seed particles and varying laser energies in polyacrylamide hydrogels of known concentration. Using a Quadratic law Kelvin-Voigt material model, we implemented ensemble-based data assimilation (DA) techniques to robustly quantify the nonlinear constitutive material parameters, up through the first, second, and third bubble collapse cycles. Fitted values were then used to simulate bubble dynamics to compute critical bubble collapse Mach numbers, and to assess time-varying uncertainties of the full cavitation dynamics with respect to the current state-of-the art theoretical model featured in the IMR model.

Results

While varying laser energy modulated bubble amplitude, seed particles successfully expanded (more than doubled) the finite deformation regime (i.e., maximum material stretch, λₘₐₓ ≈ 4 - 9). Comparing experimental data to IMR simulations, we found that fitting beyond the first bubble collapse, as well as increasing laser energy, increased the bubble radius fit error, and larger λₘₐₓ values exhibited increasingly violent bubble behavior (marked by increasing collapse Mach numbers greater than 0.08). Additionally, time-varying analysis showed the greatest model uncertainty during initial bubble collapse, where bubbles nucleated at lower laser energies and resulting λₘₐₓ had less uncertainty at collapse compared to higher laser energy and λₘₐₓ cases.

Conclusions

This study indicates IMR’s current theoretical framework might be lacking important additional cavitation and/or material physics. However, expanding the finite deformation regime of soft materials to attain lower stretch regimes enables broader applicability to a larger class of soft polymeric materials and will enable future, systematic development and incorporation of more complex physics and constitutive models including damage and failure mechanisms into the theoretical framework of IMR.

Additional Information

© Society for Experimental Mechanics 2022. Received 27 October 2021; Accepted 19 April 2022; Published 17 May 2022. The authors thank Harry C. Cramer III, Dr. Mauro Rodriguez, and Dr. Spencer Bryngelson for fruitful discussions regarding the cavitation dynamics. We gratefully thank Alice Lux Fawzi for her involvement in organizing this project. We also thank Richard Knoll at the Nanoscale Imaging and Analysis Center (University of Wisconsin - Madison) for assistance in Scanning Electron Microscopy, and Todd Rumbagh at Hadland Imaging for assistance with high-speed imaging. Funding was provided by Dr. Timothy Bentley at the Office of Naval Research through grants N00014-20-1-2408 and N00014-17-1-2058. The authors declare that they have no conflict of interest.

Additional details

Created:
August 22, 2023
Modified:
January 23, 2024