Abstract
The authors developed an active ultrasonic propagation system using fiber Bragg grating (FBG) sensors as ultrasonic receivers for structural health monitoring. Then the function of the system was extended to detect large strain waves caused by impact loads. In the large strain case, however, the relation between the Bragg waveljpnth and outputs of arrayed waveguide gratings (AWG) filter becomes nonlinear. In order to compensate the nonlinearity, an inverse calculation method had been developed. However that method has a problem that discontinuity points appear in the reconstructed waveform. Hence we improved the inverse calculation method. As a result, we succeeded in reconstruction of the impact strain waves precisely and full-automatically. Furthermore, this method could be applied to multiplexed three FBG sensors bonded on the surface of a carbon fiber reinforced plastic (CFRP) quasi-isotropic laminate on which an impact load was applied. In near future, therefore, we will attempt to identify the impact location using wavelet transform for the received waves.
