Piezoelectric PVDF smart fibre for composite applications

This research project aims to use the braiding manufacturing technique to produce a Polyvinylidene Fluoride (PVDF) 'smart fibre'. The smart fibre is a piezoelectric co-axial cable comprised of a conductive core electrode, piezoelectric PVDF-braided yarns, and a conductive wire outer electrode. A custom-design poling apparatus has been fabricated to induce a permanent piezoelectric effect into the PVDF yarns-using, whilst no inner core electrode, based on utilising the Simultaneous Stretching and Corona Poling (SSPC) technique. This method is advantageous in terms of avoiding the challenges associated with the use of in-line poling techniques, which are commonly used for the manufacturing of fibre-based piezoelectric PVDF sensors/energy harvesters via conventional hot-melt extrusion methods. A secondary method of poling was also investigated through incorporating a 0.4 mm copper wire core electrode with eight braided strands of a 0.1mm copper wire outer electrode, which are connected to a source of high-voltage DC potential to create a high electric field on the PVDF-braided structure in-between. In addition, a series of tensile tests were carried out on the PVDF-braided conductive core wires including: Zylone 1 /Copper-coated, Vectran 2 /Copper-coated, and Polyamide 66 (PA66)/Silver-coated wires; where it was observed that the piezo element sensitivity to the external mechanical stimuli could be improved when using a stiffer core electrode material. A CAD and FE model of a 100 mm gauge-length of the smart fibre with associated inner and outer electrodes, were also developed using Solidworks and COMSOL Multiphysics 5.2 software, respectively