Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Engineering Science

Program

Mechanical and Materials Engineering

Supervisor

Liying Jiang

Abstract

Elastomers are polymeric materials that consist of highly mobile long-molecule chains jointed together through crosslinking. The behavior of elastomers is commonly manifested by hyperelasticity and viscosity due to their molecular structure. Any variation of the material microstructure may have an impact on the macroscopic properties of elastomers. Therefore, characterizing the material properties of elastomers with appropriate constitutive models is essential to facilitating their potential applications. Although various constitutive models have been developed to describe the hyperelastic and viscoelastic behaviors of elastomers, it is still challenging to quantify the material properties of elastomers since there exist restrictions and limitations of the constitutive models. This thesis work attempts to develop a material property characterization package that consists of a constitutive model database and the corresponding selection strategy. The constitutive model database is established by adopting various constitutive models to the continuum mechanics framework with the incorporation of nonlinear material viscosity based on polymer dynamics. The feasibility and capability of the material property characterization package is validated by the commonly used filled and unfilled elastomers under different loading conditions, demonstrating a good agreement between the theoretical predictions of the material response and the experimental data. The developed framework is expected to work as a general platform for material property characterization of elastomeric materials.

Summary for Lay Audience

Elastomers are widely used in many areas, including automobiles, aerospace, consumer products, industrial products, medical products, etc. Due to their molecular structure, elastomers are characterized by the capability of sustaining large deformation, which enables their potential applications in the cutting-edge fields of actuation, soft robotics, biomimetics, and energy harvesting in addition to daily uses. The advancement of various applications is contingent on a better understanding of the hyperelastic and viscoelastic behaviors of elastomers, which have gained extensive attention from the research community.

In the literature, various constitutive models have been proposed to characterize the hyperelastic and viscoelastic behaviors of elastomers under different loading conditions. As these constitutive models are developed based on different hypotheses, they may have certain limitations in capturing the material responses of elastomers. It is also found that any variation of the material microstructure, such as chemical composition, degree of polymerization, extensibility of polymer chains, molecular weight of polymer chains, cross-linking density, and amount of chain entanglement, may have an essential impact on the overall properties of elastomers. To facilitate the full potential applications of elastomers, it is essential to find appropriate constitutive models to quantify the material responses. It is therefore the objective of this thesis to develop a material property characterization package for constitutive model selection and material properties identification. Validated by three commonly used elastomers, the developed material property characterization package is expected to establish a general platform for the material property characterization of new elastomeric materials.

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