Characterisation of piezoelectric PVDF monofilaments

The piezoelectric effect of poly( vinylidene fluoride) is demonstrated in monofilaments. These fibres produce electrical signal upon mechanical deformation. The structure of the monofilaments is analysed by wide angle X-ray diffraction and differential scanning calorimetry, whereas the crystalline fraction mainly consists of the piezoelectric beta phase. For polarisation and electromechanical characterisation, poly(vinylidene fluoride)-epoxy composites are manufactured, whereas all the filaments are aligned parallel to the composite structure. The electric signal is two magnitudes of order larger for the polarised samples compared to the unpolarised ones. Furthermore, there is a clear anisotropy, allowing the direction dependent measurement of stress and strain. Mechanical stress in the fibre direction produces a much larger signal compared to the same stress in the perpendicular direction.