2000 年 49 巻 4 号 p. 401-405
The termite bites and chews the wood and this causes microfractures in the wood. The authors have detected the acoustic emission (AE) generated by the microfractures and confirmed the feasibility of AE monitoring as a non-destructive inspection method to detect termite attack in wooden houses. In this study, the feasibility of piezoelectric polymer, PVDF (polyvinylidene fluoride) as an AE sensor was investigated. Flexible PVDF film of 40μm inserted between the jointing surfaces of wooden posts of 105mm by 45mm in square could detect the artificial AEs generated by the breaking of pencil lead and the AEs generated by termite attack. AE amplitude increased in accordance with the pressure applied to posts up to about 1MPa. Due to the anisotropy of the AE attenuation in the wood, the monitoring area of a PVDF film inserted between the end-end surfaces of the posts was larger the film between the end-side surfaces. The higher AE amplitude was obtained by sandwiching the PVDF film by a pair of elastic Teflon sheet of 0.5mm thick to get an intimate contact among the film and the posts. The sensitivity of the one of the three-layered PVDF film about two times larger than the PVDF film of 40μm.