Modeling of Carbon Nanotube Reinforced Rubber Seals

The increasing demand for oil and gas has incited exploration and production of deeper wells that reach high pressure and high temperature (HPHT) reservoirs. One critical element that is required to this end is rubber seals that can withstand HPHT conditions while meeting the requirements of sealability and structural integrity. Novel nanocomposites that comprise of natural rubber (NR) reinforced by well dispersed, high-concentration carbon nanotubes (CNTs) were recently developed to achieve the desired performance and were experimentally shown to exhibit significantly higher storage modulus than the matrix material. Understanding of the underlying reinforcing mechanism of this class of nanocomposites subjected to large deformation, especially in the real application conditions, has been very limited. In this study, a multiscale modeling method is developed to understand the mechanical behavior of CNT-rubber seals installed in a groove and subjected to high pressure. A micromechanics model is first constructed to evaluate the effective stress-strain responses of a representative volume element under different loading conditions, including uniaxial tension, equal biaxial extension, and planar tension. The effective properties thus established are then inputted into an appropriate hyperelasticity model, which is then used to model a CNT-rubber O-ring installed and pressurized. Sealability and structural integrity are evaluated in terms of contact pressure and strain. The numerical results are compared with the available experimental data. A parametric study is then conducted to assess the effects of CNT concentrations.