Fabrication of piezoelectric fiber composites by the double cutting–filling method and properties characterisation

Abstract

Fine-scaled piezoelectric fiber composites (PFCs) were successfully fabricated by the so-called double cutting–filling method developed in this research. The fabricated PFCs consisted of interdigitated electrodes, epoxy resin and piezoelectric fibers. The microstructure, piezoelectric properties, mechanical properties, free strain and sensing properties of the fabricated PFCs were characterized. It has been found that the fabricated PFCs with an active area of 50 × 30 mm² exhibited good coupling between the electrodes and fibers, which is highly required. The relative dielectric constant (ε_r) and dielectric loss (tan δ) of the fabricated PFCs were 1961 and 0.054, respectively. The tensile strength reached 49.28 MPa and 36.18 MPa in the longitudinal and transverse directions, respectively, indicating that high and comparable tensile strength was achieved in both directions. The longitudinal free strain of the PFCs reached about 1400 με and the transverse free strain 680 με at a 2 kV peak-to-peak sinusoidal alternating voltage, suggesting that the PFCs exhibited good orthotropic properties, as desired. The longitudinal piezoelectric coefficient (d₃₃) of the PFCs reached 518 pC N⁻¹. The fabricated PFCs also exhibited desirable anisotropic sensing properties which can be utilized to quantify the origin of excitation in damage detection of composites. The PFCs developed in this study featured excellent piezoelectric and mechanical properties, high free strain, desirable orthotropic mechanical properties and excellent anisotropic sensing properties, which helps to extend their applications in self-diagnosis and adaptive smart structures.