Attenuation of Ultrasound by Hollow Ceramic Spheres Embedded Within a Curing Resin

The basic technology of using embedded acoustic waveguides (AWG) for cure and NDE monitoring of resins and composite materials has evolved[1–11] over the last forty years. A recent paper[11] describes new applications of AWG in which acoustic wave transmissions between two embedded waveguides allows cure monitoring of large areas of a composite panel and also, in principle, the sensing of voids occurring during curing (simulated by burying hollow ceramic spheres within a composite panel). A surprising result was the system sensitivity, as the presence of only 0.16% by volume of hollow ceramic spheres could be detected. This result prompted the more detailed study reported here of ultrasound attenuation by voids (hollow ceramic spheres) embedded within a curing resin