Acknowledgent:
The paper was first published at the Conference on NDE applied to Composite Fabrication,
organized by NTIAC and McDonnell Douglas Aerospace and took place in St. Louis Missouri in Oct '94.
See also all 54 NDE Abstracts of the '94 and '96 Conference Proceedings.

ABSTRACT

Measurements of the ultrasonic sound speed of thermosetting resins and composites can be used as an in-process cure monitoring technique. Ultrasonic measurements have an advantage over other in-process techniques in that ultrasonic sensors do not make contact with the part (thus leaving no imbedded sensor or witness mark) and can make true bulk measurements of the part. A new commercially available ultrasonic cure monitoring system has been developed which easily enables ultrasonic measurements to be made in compression molding, resin transfer molding, and autoclave processes. Advancements in ultrasonic sensor technology enable the self-contained ultrasonic sensor to easily installed in a mold and maintain good coupling to the part during thermal cycling to 260 C. Data is presented showing the change in ultrasonic sound speed during the compression molding of a graphite-epoxy prepreg. The data shows a good relationship to the ionic conductivity and resistivity data collected via dielectric cure monitoring.

TABLE OF CONTENTS Full Text



1. INTRODUCTION
2. ULTRASONIC MEASUREMENT TECHNIQUE
3. ULTRASONIC MEASUREMENT SYSTEM
4. EXPERIMENTAL RESULTS
5. FUTURE WORK
6. CONCLUSIONS
7. REFERENCES