This thesis reports for the first time the fabrication and characterisation of novel electroactive ceramic/polymer composite films of calcium modified lead titanate (PTCa) and poly (ether ketone ketone). Composite sensors with different concentrations of ceramic were fabricated using a hot pressing technique. The PTCa ceramic was treated using titanate coupling agent in order to improve sample quality. Dielectric measurements have been performed to study sample characteristics. Piezoelectric and pyroelectric properties of the composites have been measured and the mixed connectivity cube model used to detennine the relative amounts of 0-3 and 1-3 connectivity. The advantages and limitations of the model have been discussed. Additionally, some mechanical properties of the composites have been assessed to study their potential ability to detect acoustic emission (AE) in carbon fibre reinforced composites (CFRC). The composite sensors were placed on and inserted into different panels in order to compare their ability to detect AE in both surface mounted and embedded modes. The composite sensors have been shown to have less sensitivity than the low profile lead zirconium titanate (PZT) ceramic and the porous polypropylene (PP) polymer sensors, but they were found to have more suitable mechanical and thermal properties than the ceramic and polymer respectively for embeddeding in CFRC panels. PTCa/PEKK 60/40% sensors embedded in a CFRC panel have been shown to be capable of detecting the two components of the plate waves, namely, extensional and flexural mode. In addition, it has been shown that the surface mounted PTCa/PEKK composites with 60% volume of ceramic loading can locate simulated AE with high accuracy using triangulation techniques. Finally, it has been shown that the sensors can detect real AE from fibre delamination in a CFRC beam.