TY - JOUR
T1 - Characterization of visco-hyperelastic behavior of open cell polyurethane foam through transient shear testing
AU - Dalisay, Jon Dewitt E.
AU - Liu, Lejie
AU - Eriten, Melih
AU - Bergman, Lawrence A.
AU - Vakakis, Alexander F.
N1 - This work was supported in part by the National Science Foundation Grants CMMI-CAREER 1554146 and CMMI-17-1727761. The support by the Faculty Development Scholarship, Engineering Research and Development for Technology Program, Department of Science and Technology, Government of the Philippines (PH-DOST) is gratefully acknowledged. Any opinion, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of PH-DOST. Also, the financial support of the Department of Mechanical Science and Engineering, University of Illinois, Urbana – Champaign is gratefully acknowledged.
PY - 2022/4/1
Y1 - 2022/4/1
N2 - Soft materials find ever-growing use in load-bearing applications, and hence, there is an imminent need for accurate testing and modeling of their mechanical properties. Nonlinearities and rate-dependence are inherent in the mechanical response of such materials, thanks to their multiphasic flexible constituents. Fragility of soft materials and rapid changes in their constituents depending on the environment add further challenges in mechanical characterization. This study introduces an efficient methodology to measure nonlinear viscoelastic properties of soft materials from transient shear response and validates the methodology experimentally on flexible polyurethane foams. Direct estimation of friction forces due to the Poynting effect and independent uniaxial compression tests of the same foam are also documented, validating the characterization framework. Both methods deliver comparable results with the transient-shear-based framework. Simple sample preparation and installation further complements the reliable and quick estimation capability, and thus offers a suitable characterization methodology for fragile and time-sensitive samples such as biological tissues. While validating the proposed framework on foams, fast relaxations and sensitivity to peak strains and strain rates are observed. Buckling and failure of the foam in the vicinity of the inertial plate could be possible explanations of those observations. Besides estimating the visco-hyperelastic properties of the foams, the tester dissipation stemming from material and frictional damping is also estimated in the framework. Increases in frictional dissipation due to compromised lubrication in guide rails over a period of three days are observed to shorten transients. Proper lubrication and control of friction before each test suppresses stochastic dry friction and improves repeatability and accuracy of the material characterization methodology.
AB - Soft materials find ever-growing use in load-bearing applications, and hence, there is an imminent need for accurate testing and modeling of their mechanical properties. Nonlinearities and rate-dependence are inherent in the mechanical response of such materials, thanks to their multiphasic flexible constituents. Fragility of soft materials and rapid changes in their constituents depending on the environment add further challenges in mechanical characterization. This study introduces an efficient methodology to measure nonlinear viscoelastic properties of soft materials from transient shear response and validates the methodology experimentally on flexible polyurethane foams. Direct estimation of friction forces due to the Poynting effect and independent uniaxial compression tests of the same foam are also documented, validating the characterization framework. Both methods deliver comparable results with the transient-shear-based framework. Simple sample preparation and installation further complements the reliable and quick estimation capability, and thus offers a suitable characterization methodology for fragile and time-sensitive samples such as biological tissues. While validating the proposed framework on foams, fast relaxations and sensitivity to peak strains and strain rates are observed. Buckling and failure of the foam in the vicinity of the inertial plate could be possible explanations of those observations. Besides estimating the visco-hyperelastic properties of the foams, the tester dissipation stemming from material and frictional damping is also estimated in the framework. Increases in frictional dissipation due to compromised lubrication in guide rails over a period of three days are observed to shorten transients. Proper lubrication and control of friction before each test suppresses stochastic dry friction and improves repeatability and accuracy of the material characterization methodology.
KW - Friction
KW - Nonlinear elasticity
KW - Simple shear
KW - Transient vibrations
KW - Viscoelasticity
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U2 - 10.1016/j.ijsolstr.2022.111482
DO - 10.1016/j.ijsolstr.2022.111482
M3 - Article
AN - SCOPUS:85124397623
SN - 0020-7683
VL - 241
JO - International Journal of Solids and Structures
JF - International Journal of Solids and Structures
M1 - 111482
ER -