NEGATIVE POISSON RATIOS AND STRAIN-DEPENDENT MECHANICAL-PROPERTIES INARTERIAL PROSTHESES

The elastic properties of two artificial arterial prostheses have been measured. One is a fibrillar polyurethane (PU) material, the other is an expanded polytetrafluoroethylene (ex-PTFE). It is shown that the c onventional assumption of incompressibility is invalid for both materi als and that changes in the thickness of the prosthetic artery wail mu st be measured directly. The ex-PTFE shows highly strain-dependent pro perties, the most significant being that of large negative through-thi ckness Poisson ratios, up to -11. These results have important consequ ences for matching the properties of prostheses to natural materials.