Piezoelectric composites, consisting of a ferroelectric ceramic powder of calcium‐modified lead titanate dispersed in two different polymer matrices, viz. from vinylidene fluoride trifluoroethylene and an epoxy, have been fabricated. The composites show a mixed connectivity structure, and the results of electromechanical characterization are given. Thin films of these materials have been incorporated into surface mounted acoustic emission sensors and their frequency response and ability to detect plate waves, generated by a simulated acoustic emission source, has been examined. In situ transducers embedded into glass‐reinforced laminate plates have also been examined and have been shown suitable for acoustic emission sensors.

Composites of ferroelectric ceramic in polymer matrix have been developed and characterized for their ability to be employed as embedded sensors for the health monitoring of olymer composite structures. In this paper results illustrating the response of embedded composite sensors to dynamic loads are presented and discussed. Furthermore, the ability of the composite sensors to act as actuators, generating diagnostic waves in composite structures, has been investigated.

Aberdeen Proving Ground, Maryland 21 005-5069Mixed connectivity composites consisting of a ferroelectric ceramic powder of calcium modified lead titanate dispersed in a polymer matrix have been fabricated into piezoelectric bimorph sensors. The piezoelectric, dielectric and electromechanical coupling coefficients of these sensors have been measured and a full characterization of the electromechanical properties are reported. The suitability of these bimorph transducers as in-situ acoustic emission sensors, embedded into glassepoxy laminate plate like structures, has been investigated. A comparison of the performance of these sensors to those of previously investigated monomorph sensors fabricated from the same material has been made. SCIENCE, MARCH 1999, V d . 39, No. 3 508 POLYMER ENGINEERING AND

Two different mixed connectivity composites, consisting of a ferroelectric ceramic powder of calcium modified lead titanate ( m a ) dispersed in a polymer matrix, have been fabricated and their ferroelectric properties have been investigated. Hysteresis measurements have been conducted on composites of FTCa with a polar polymer of polyvinylidene trifluoroethylene (P(VDF-TrFE)) and PTCa with a thermosetting epoxy resin to determine the coercive fields and remanent polarization of the two different composites. The composites show noticeable differences in their behavior during poling along with the values of their piezoelectric coefficients, with the composite of €TCa/P(VDF-'IYFE) showing enhanced piezoelectric activity over that of FTCa/epoxy. This paper reports on the polarkation properties and the microstructural nature of the composites.

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