Fatigue behavior of a pyrolytic carbon.

The test method introduced here enables the fatigue test of a brittle material at a stress level that is as high as its ultimate fracture strength. The procedural design of the test eliminates uncertainties that often make interpretation of the results difficult. The results, using a statistical analysis, demonstrate that isotropic pyrolytic carbons are fatigue-free in physiologically relevant stress regimes encountered in contemporary bi-leaflet artificial heart-valve designs. Verification tests show that the material can withstand cyclic stress of 10(9) cycles at a strain level that equals that of the mean static strength.