A NEW ULTRASONIC MEASUREMENT SYSTEM FOR THE CURE MONITORING OF THERMOSETTING RESINS AND COMPOSITES

Measurements of the ultrasonic sound speed of thermosetting resins and composites can be used as an in-process cure monitoring technique. Ul trasonic measurements have an advantage over other in-process techniqu es in that ultrasonic sensors do not make contact with the part (thus leaving no imbedded sensor or witness mark) and can make true bulk mea surements of the part. A new commercially available ultrasonic cure mo nitoring system has been developed which easily enables ultrasonic mea surements to be made in compression molding, resin transfer molding, a nd autoclave processes. Advancements in ultrasonic sensor technology e nable the sensor to maintain good coupling to the part during thermal cycling to 260 degrees C. Data is presented showing the change in ultr asonic 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.