Characterization of clay nanoparticle-containing poly(vinylidene fluoride-trifluoroethylene) copolymer for piezoelectric sensors

Organically modified montmorillonite (OMMT) was added to a poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE) copolymer at different concentrations (0-3 wt%) to increase its piezoelectric and mechanical properties. Additionally, three different treatments of heating-cooling, electrical poling, and pressing were used to enhance the β-phase fraction in P(VDF-TrFE)/OMMT (PVTO) composite films. Furthermore, various experimental tests (tensile, creep, and electromechanical) were carried out to assess the feasibility of PVTO film sensors for health monitoring of composite structures. From the results, it was proved that the effect of OMMT on the formation of β-phase in P(VDF-TrFE) was caused mainly by the ion-dipole interactions between P(VDF-TrFE) and OMMT. The sequential process of “heating-cooling-pressing-electrical poling” (heating: 140 °C for 24 h, cooling: −10 °C, pressing: 30 MPa for 15 min, electrical poling: 80 MV/m for 30 min) was the most effective way to maximize the β fraction in PVTO. PVTO sensors successfully survived in a carbon/epoxy laminate, generating electrical signals of 1.6, 1.8, 2, and 4 V for PVTO with an OMMT content of 0, 1, 2, and 3 wt%, respectively, under a periodic compressive force of 177 kPa.