OS0702 CFRP構造の損傷検知へのTFDRの適用

Abstract

Carbon fiber reinforced polymer (CFRP) composites have higher specific strength and specific stiffness than conventional metallic materials. The CFRP structures, however, are easily damaged by impact loading. It is quite difficult to detect internal damages caused by impacts by visual inspection. In the present paper, self-sensing time-frequency-domain reflectometry (TFDR) is proposed as a damage detection method for large CFRP structures. In the TFDR a set of high-frequency burst signals is applied to a structure and damage location is calculated from difference in time of arrival between an input signal and reflected signal from the structure end. By using several signals with different frequencies, other information such as dimensions of damage can be obtained. This is one of the great advantages to using the frequency domain reflectometry. The TFDR uses both methods; one estimates damage location and the other identifies its dimensions. The purpose of this study is to verify the applicability of the TFDR to CFRP structures. In the TFDR, after experiment for damage detection using the time domain reflectometry (TDR) with electromagnetic waves flowing in a long UD CFRP (1980 mm×120 mm) in the transverse direction, the frequency characteristics of the wave in the CFRP structure are investigated by the finite difference time domain (FDTD) analysis. As a result, the experiment indicated that the TDR could detect a notch in the CFRP using waves flowing in the transverse direction. The electromagnetic analyses showed that the TFDR was able to detect damage and identify its location and dimensions of CFRP structures.