Microacoustical NDE of Pyrocarbon Materials for Cardiovascular Prosthetic Application

Effective, non-destructive methods of structure and mechanical property evaluation have been proposed for isotropic pyrocarbons, which are widely applied in medical prosthetic area. This study on the elastic property of low-temperature pyrolitic carbon was based on experimental analysis of sound velocity data. It has been shown that weak elastic anisotropy is inherent to pyrocarbon materials. Due to the study, pyrocarbons can be classified onto three types: isotropic, transversally isotropic and anisotropic. A full matrix of elastic constants for transversally isotropic pyrocarbon has been measured. Acoustic images of the internal pyrocarbon structure (B and C-scans) are presented in the paper. The images show that the low-temperature
pyrocarbons have a bulk microlayered structure, and that it can be the reason for material anisotropy. Different kinds of microstructural defects, which are caused by features of pyrocarbon technology, can be detected with microacoustical techniques.

Keywords: Pyrolitic Carbon, Acoustic Microscopy Measurements, Elastic Properties, microstructure