Nondestructive damage detection and interfacial evaluation of single-fibers/epoxy composites using PZT, PVDF and P(VDF-TrFE) copolymer sensors

Damage sensing and interfacial evaluation of single-glass or basalt fibers/epoxy composites were performed by micromechanical technique and acoustic emission (AE). Piezoelectric lead–zirconate–titanate (PZT), polyvinylidene fluoride (PVDF) and poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymer were used as AE sensor, respectively. In single-fiber composite, the damage sensing and interfacial properties with different sensor types were compared with each other. Piezoelectric PVDF polymer sensor was attached or embedded in the composite, whereas PZT sensor was only attached on the surface of specimen. For glass fiber/epoxy composite, the fiber fracture, matrix crack and possible interfacial debonding signals were detected by PZT sensor, whereas the fiber fracture signals were detected mainly by PVDF sensor because the sensitivity of PZT sensor was higher than that of PVDF sensor. The sensitivity of P(VDF-TrFE) copolymer sensor was rather higher compared with conventional PVDF sensor case. In case of embedded polymer sensors, responding sensitivity was higher than that of the attached case. It can be due to fully constraint inside specimen to transfer elastic wave coming from micro-deformation well.