抄録
The internal damage evolution of thin tubular specimens of CFRP was studied by means of AE (acoustic emission) measurement. The AE signals were detected first in the quasi static tests on the CFRP tubular specimens of 0°, 90° and ±45° fiber orientations, and three damage modes induced in the tests, i.e., matrix crack, delamination and fiber breakage were identified by the frequency analysis of AE signals. Then, the fatigue tests on the specimens of ±45° were performed under the particular stress ratios R=0 and R=-0.25 by detecting the AE signals for the whole process of fatigue. By use of the results of the quasi static tests, the behavior of damage development in every stage of fatigue was analyzed from the frequency analysis of AE signals. The AE signal related with matrix crack was observed in the middle of the fatigue process, and the AE signal due to fiber breakage was observed in the later stage of the fatigue. The AE signal due to delamination was mainly observed in the later period of the fatigue under stress ratio R=-0.25. The damage state in some stages of fatigue was also observed by a scanning acoustic microscope by interrupting the fatigue test, and the validity of the identification of damage modes by the frequency analysis was confirmed by comparing the results of AE analysis with those of the internal observation. These results agreed also with the results of other measurement of the macroscopic variation of elastic modulus, as well as with those of damage observation on the sliced section of the specimens.
