Koichi Mizukami

Analytical solutions to eddy current in carbon fiber-reinforced composites induced by line current

This paper presents analytical solutions to eddy current distribution in carbon fiber-reinforced plastics induced by line current. Derived solutions show that eddy current distribution in unidirectional carbon fiber composite is dependent only on electrical conductivity in the drive current direction when the drive current is directed in the fiber direction or the transverse direction. Moreover, according to the derived analytical solution, skin depth of eddy current depends not only on frequency of drive current but on lift-off and width of the drive current unlike general expression of skin depth. Finally, we discuss improvement of sensitivity of eddy current conductivity sensor using analytical solutions. It is found that analytical solutions can clearly divide effects of magnetic field from drive current and that from eddy current. Sensitivity of eddy current sensor can be improved by 10 times placing pickup coil at region where the effect of magnetic field from eddy current is large.

Evaluation of size of surface and subsurface waviness in carbon fiber composites using eddy current testing: a numerical study

An eddy current method to evaluate size of waviness in carbon fiber reinforced plastics is studied. It is shown that the shape of the waviness appears as a deformation of the magnetic field distribution. Finite element method analyses are performed to investigate relationships between the size of the waviness and that of the magnetic field deformation. The waviness length can be accurately estimated from the length of the magnetic field deformation. It is found that the amplitude of the magnetic field deformation decreases with waviness depth in a certain proportion that is independent of the waviness amplitude. Using these characteristics, the range of the waviness amplitude is obtained. The effect of waviness in multiple layers on waviness size evaluation is also investigated. It is revealed that multiple waviness causes either overestimation or underestimation of the upper limit of the waviness amplitude depending on the directions of constituent waviness.