| 초록 |
Polyvinylidene fluoride (PVDF) film can be used as a polymer sensor and has high flexibility and mechanical toughness, whereas lead-zirconate-titanate (PZT) is brittle due to ceramic nature. Nondestructive damage sensitivity and source location of single-basalt fiber/epoxy composites with PZT, PVDF and poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE) sensors were investigated using micromechanical test and acoustic emissions (AE). Polymeric sensor was damaged with various temperature ranges and then sensitivity was compared to each other. Sensitivity of two polymeric sensor for fiber fracture was rather lower with small error range compared to PZT sensor, whereas sensitivity decreased significantly at high thermal damage temperature. For PZT and PVDF sensors, waveforms of epoxy resin were analyzed for different impact directions, air bubble and surface damage with vertical, longitudinal and diagonal scratches. In cases of surface damage or air bubble, the signals were much smaller than those of no damage case. For top impact, flexural wave appeared dominantly, whereas for side impact extensional wave was observed obviously. Arrival time with increasing damage density such as surface scratch and internal air bubble was longer due to their damping effect. Acknowledgement: This study was supported by NRL program, MOST through KRISS, via ReCAPT, GNU. |
