Mechanical energy dissipation modeling of exfoliated graphite based on interfacial friction theory

Mechanical energy dissipation is important for vibration damping and sound absorption. This paper provides an analytical model for the interfacial-friction-based viscous behavior of exfoliated graphite, thereby establishing a methodology that may be applied to such behavior of materials in general. This model is in contrast to the conventional bulk viscous deformation model. It can be used to predict the viscous behavior (e.g., loss modulus) from the material properties. A dimensionless deformation factor is introduced to describe the off-axis dimensional change upon viscous deformation. The interfacial-friction-based energy loss is calculated from the equivalent friction force and equivalent sliding displacement, which are in phase during dynamic sinusoidal flexural loading. Each cell in exfoliated graphite is modeled as a pore bounded by Voigt-element-based cell walls, which have merged in order to form the cellular structure. The viscous behavior stems primarily from the sliding between the merged cell walls. The contribution of sliding between graphite layers within a cell wall is negligible. The greater is the solid content, the smaller is the displacement, the higher is the friction force, the less is the energy loss and the lower is the degree of viscous character. Excellent agreement is obtained between the modeling and experimental results.