THIN FILM SAW DEVICES FOR IN SITU MONITORING OF COMPOSITE PROCESSES

The use of fibrous composites has greatly increased in the Navy. These composites have introduced challenging problem in process manufacturing of these materials. Dielectric sensors as well as ultrasonic embedded wave guides have been successful in cure monitoring; however, they have two severe handicaps: 1. Placement is limited to trimmings since the inclusions weaken the material; 2. The region monitored by the sensors is very small compared to the size of typical parts, requiring an impractical number of sensors. Thin film sensors,capable of covering the entire part, would solve both these problems. The proposed research, drawing on the well-developed technologies of thin film deposition and acoustic devices, would advance and adopt the surface acoustic wave (SAW) device technique to develop thin film/foil distributed sensor surfaces. Thus the proven technique of ultrasonic cure monitoring can be made noninvasive and effective over the entire surface of tools used in production. Phase I efforts will etch surface wave (Rayleigh & L-cr) devices on the tools and construct piezoelectric sensor foils that can be attached to the surface tools or placed in the lining of vacuum bags. Testing will be done on small composite plates. Phase II efforts will advance to life-size samples.