Ultrasonic cure monitoring of advanced composites

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 for the cure monitoring of thermosetting resins and composites has been developed. Advancements in ultrasonic sensor technology enable the self‐contained ultrasonic sensor to be easily installed in a mold and maintain good coupling to the part during thermal cycling to 260°C. Data are presented showing the change in ultrasonic sound speed during the compression molding of epoxy prepregs. The data show a good relationship to the electrical resistivity data collected via dielectric cure monitoring. The ultrasonic technique is also applicable to phenolic based materials.