Abstract
This paper presents impedance response to alternating current in a CFRP unidirectional (UD) laminate. Firstly, impedance and its phase angle for frequency ranging from 1 kHz to 1 MHz were measured for the specimens with various off-axis angles. Secondly, change in impedance during tensile loading was measured for the above specimens. Finally, a simple model was proposed to express impedance properties of a UD laminate using an equivalent electric circuit. The norm of impedance is almost independent of frequency for all off-axis angles. The phase angle is kept to be constant for the off-axis angle below 45°while it becomes negative at high frequency for the off-axis angle larger than 60°. This behavior is expressed by an equivalent circuit model introducing a capacitance element. Impedance response to mechanical strain is almost linear for all the off-axis angles. Piezoresistance behavior at low strain was characterized on the basis of the above model.
