Nonlinearly elastic and anisotropic constitutive model for ePTFE vascular graft based on tensile and inflation experiments

Abstract

The long-term success of interventions in cardiovascular medicine can be enhanced by the computer-assisted planning of these procedures. However, the reliability of all computational simulations depends significantly on the input parameters. One of the most important is the constitutive model for the biological tissue and for the implant material. While the last few decades have brought great advances in modeling the mechanical properties of the arterial wall, synthetic grafts have not received as much attention. The primary goal of our research is to contribute to filling this gap. Our study is focused on determining a constitutive model for ePTFE vascular grafts. Uniaxial tensile experiments with strips cut from tubular vascular grafts SA1802 (Gore-Tex Stretch Vascular Graft - Large diameter) in the circumferential and longitudinal direction, and pressurization experiments with intact graft tubes V06010L (Gore-Tex Vascular Graft - Standard-walled) were carried out. A nonlinearly elastic anisotropic model was used to describe the mechanical response observed in these experiments. The four-fiber hyperelastic model based on the exponential function combined with the neo-Hookean term was able to fit the data observed in both the uniaxial tensile and inflation-extension experiments with one single set of parameters. Thus, the resulting model is suitable to be used in numerical simulations studying surgical procedures involving ePTFE vascular grafts in the mechanical states of uniaxial as well as multiaxial stress.