Description
- Abstract:
- Elastomeric foams are widely used for impact protection due to their ability to undergo large, reversible deformations and absorb large amounts of energy. A predictive model of their time-dependent, large-deformation mechanical behavior is needed for use in design. This thesis addresses several problems related to the constitutive modeling of elastomeric foams: • At quasi-static strain rates, the material response in simple compression/tension is highly nonlinear and shows substantial asymmetry between tension and compression. The response in compression is particularly complex. The response is initially linear, but as the axial strain magnitude increases, the response gradually transitions into a “plateau” in which both the axial stress and the lateral strain vary minimally as the axial strain magnitude increases. We propose a phenomenological, isotropic, finitedeformation, hyperelastic constitutive model based on invariants of the logarithmic, Hencky strain that is able to capture the material response. A systematic procedure for material parameter estimation is provided. • At higher strain rates, due to the viscoelasticity of the matrix, many elastomeric foams display a highly dissipative, time-dependent mechanical response, manifesting in rate-dependence and hysteresis under reversed loading. We propose a viscoelastic model based on a multi-mechanism, multiplicative-decomposition based strategy. The model consists of a time-independent, hyperelastic contribution and several timedependent, viscoelastic contributions that employ the multiplicative decomposition of the deformation gradient into non-equilibrium elastic and viscous parts. • Different foam materials exhibit different rate-dependent behavior due to their porous structures and matrix material types. The phenomenological modeling framework proposed in this thesis is able to accommodate this by utilizing a flexible flow rule and a flexible non-equilibrium free energy density function for the viscoelastic contributions. We show that the model framework may be applied to both open-cell and closed-cell elastomeric foams and validate the predictive capability of the calibrated model for several materials in multiple cases that involve inhomogeneous deformation.
- Notes:
- Thesis (Ph. D.)--Brown University, 2021
Citation
Li, Xiuqi,
"Large-deformation, viscoelastic constitutive modeling of elastomeric foams"
(2021).
Mechanics of Solids Theses and Dissertations.
Brown Digital Repository. Brown University Library.
https://repository.library.brown.edu/studio/item/bdr:n58ashmz/
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Mechanics of Solids Theses and Dissertations
Theses and Dissertations for the Mechanics of Solids department....