Tomographic imaging of material property variations in polymers

The use of tomographic imaging to map out material property variations in polymeric media is explored. A set of target samples was prepared with known variations in cure state. Ultrasonic transit times for multiple ray paths were measured and, from these data, tomographic images were created using a modified algebraic reconstruction technique (ART) algorithm. These data were compared with simulated data in order to evaluate the spatial-resolution capability of the approach. Qualitative agreement between the actual sample image and that computed using the ART algorithm is good. However, image smoothing at the boundary between the core region and the sample exterior precludes a sharp transition. This effect tends to make it difficult to identify anomalies in material properties when the property difference is small (<3%)