On the fractography of overload, stress corrosion, and cyclic fatigue failures in pyrolytic-carbon materials used in prosthetic heart-valve devices

A scanning electron microscopy study is reported of the nature and morphology of fracture surfaces in pyrocarbons commonly used for the manufacture of mechanical heart‐valve prostheses. Specifically, silicon‐alloyed low‐temperature‐isotropic (LT1)‐pyrolytic carbon is examined, both as a coating on g...

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Bibliographic Details
Published in:Journal of biomedical materials research 1992-01, Vol.26 (1), p.69-76
Main Authors: Ritchie, R. O., Dauskardt, R. H., Pennisi, F. J.
Format: Article
Language:English
Subjects:
Biocompatible Materials
Biological and medical sciences
Carbon
Corrosion
Graphite
Heart Valve Prosthesis
Materials Testing
Medical sciences
Microscopy, Electron, Scanning
Prosthesis Failure
Stress, Mechanical
Surgery (general aspects). Transplantations, organ and tissue grafts. Graft diseases
Surgery of the heart
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Summary:A scanning electron microscopy study is reported of the nature and morphology of fracture surfaces in pyrocarbons commonly used for the manufacture of mechanical heart‐valve prostheses. Specifically, silicon‐alloyed low‐temperature‐isotropic (LT1)‐pyrolytic carbon is examined, both as a coating on graphite and as a monolithic material, following overload, stress corrosion (static fatigue), and cyclic fatigue failures in a simulated physiological environment of 37°C Ringer's solution. It is found that, in contrast to most metallic materials yet in keeping with many ceramics, there are no distinct fracture morphologies in pyrocarbons which are characteristic of a specific mode of loading; fracture surfaces appear to be identical for both catastrophic and subcritical crack growth under either sustained or cyclic loading. We conclude that caution should be used in assigning the likely cause of failure of pyrolytic carbon heart‐valve components using fractographic examination.
ISSN:0021-9304
1097-4636
DOI:10.1002/jbm.820260107