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

✍ Scribed by Ritchie, R. O. ;Dauskardt, R. H. ;Pennisi, F. J.

• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 545 KB
• Volume: 26
• Category: Article
• ISSN: 0021-9304
• DOI: 10.1002/jbm.820260107

✦ Synopsis

A scanning electron microscopy study is reported of the nature and morphology of fracture surfaces in pyrocarbons commonly u s e d for t h e m a n u f a c t u r e of mechanical heart-valve prostheses. Specifically, silicon-alloyed low-temperaturei s o t r o p i c (LT1)-pyrolytic c a r b o n 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 e n v i r o n m e n t of 37°C Ringer's solution. It is found that, in con-trast 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 t o 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.