Cure Monitoring of Composites Using Multiple Acoustic Waveguides

In earlier [1–6] investigations the practicality of using an embedded acoustic waveguide (AWG) for cure and NDE monitoring of composites was established. More recent work has been directed toward using the acoustic wave transmission between two waveguides embedded in a parallel position for measuring cure over a larger area, and also for sensing the presence of voids during cure. In order to evaluate these concepts, Nichrome waveguides (0.5 mm diam.) were embedded 10 cm apart within graphite-epoxy (AS4/3501-6) panels of approximately 30 cm by 30 cm size. One panel had 0.16% by volume of hollow ceramic microspheres distributed between the volume enclosed by the waveguides and within the central prepreg sheets so that the concept of acoustically sensing voids formed during cure could also be evaluated