Electromechanical characterization of a single active structural fiber lamina for multifunctional composites

Piezoelectric fiber composites (PFCs) are a new group of materials recently developed in order to overcome the fragile nature of monolithic piezoceramics. However, there are some practical limitations associated with these types of materials, namely the generally separate electrode makes them difficult to embed into composites and when imbedded the low tensile properties of the material and the abnormal geometry in comparison with traditional reinforcements lead to stress concentrations reducing the material's strength. To resolve the inadequacies of current PFCs, a novel active structural fiber (ASF) was developed that can be embedded in a composite material to perform sensing and actuation, in addition to providing load bearing functionality. The ASF combines the advantages of the high tensile modulus and strength of the traditional composite reinforcements as well as the sensing and actuation properties of piezoceramic materials. A micromechanics model based on the double inclusion approach and a finite element model were been developed to study the effective piezoelectric coupling coefficient of the ASF as well as the ASF lamina. In order to evaluate the performance of the ASF when embedded in a polymer matrix and validate the model's accuracy, single fiber lamina have been fabricated and characterized through testing with an atomic force microscope. The results of our testing demonstrate the accuracy of the model and show that ASF composites could lead to load bearing composites with electromechanical coupling greater than most pure piezoelectric materials.