Modeling Mechanical Behavior of Polytetrafluoroethylene Tubes

Polytetrafluoroethylene (PTFE) is used extensively as the inner tube material in various Aerospace and Industrial hose constructs. The fluoropolymer exhibits various unique mechanical properties from other fluoropolymers including chemical inertness, non-adhesiveness and low friction coefficient making it an attractive solution for hose applications. PTFE material can be modeled using various material modeling approaches including linear-elastic, hyperelastic and viscoplastic depending on the level of accuracy required in predicting material response. Fluoropolymers, like PTFE, are considered viscoelastic-viscoplastic materials. In other words, the material exhibits both viscous and elastic characteristics when undergoing deformation but also possesses behavior in which the deformation of the material also depends on the rate by which loads are applied. As such, discrete material modeling techniques are required to accurately model the complex polymer behaviors as well as its temperature dependent loading history. From both uniaxial tension testing as well as cyclic testing of PTFE tube at various operating temperatures, the Bergstrom-Boyce-Mullins (BBM) model was selected, as this approach provides the best correlation with test data. This paper documents the methodology utilized for developing a high fidelity temperature dependent material model for PTFE tube to ultimately predict the mechanical response of Eaton’s hose assemblies with PTFE core tubes.