Development of eddy current test for the fatigue behavior in carbon/epoxy tube

The researches using the Eddy Current Test (ECT) were limited for the particle reinforced metal base composites. It had been impossible to inspect the eddy current since the carbon/epoxy tube had the low electric conductivity of resin layer. However, it has been successful for our previous research to inspect the defect using the EC. In the case of loading to carbon/epoxy tube, the researches of relationship between the failure behavior and the variation of EC signals have not been carried out. Therefore, this research focused on the comparison and the evaluation of the EC signals according to the variation of the defect depth using the unloading and the radial-loading carbon/ epoxy tube. We obtained results are as follow. Firstly, reviewing the stress distribution of carbon/ epoxy tube under the radial-loading, it was known that the defect depth did not have strongly influence on the stress distribution. Therefore, it was believed that the stress distribution was not directly related to the signals of the EC. Secondly, the EC signals similar to that of the unloading specimens could be obtained from the radial-loading specimen of 80 % defect depth. Thirdly, regardless of the unloading and the radial-loading specimens, the defect of 80 % and 100 % depths had the similar phase angles and Lissajous figures. Finally, it was guessed that the length of micro- cracks distributed at the whole specimens under the radial-loading was less than 60 % defect depth.