A new system for nondestructive and contact-free detection of fiber orien tation in fiber reinforced composites such as CFRP was devised using 35 GHz millimetric wave. In this system, by rotating the polarization of the wave and compensating it after passing through the sample, changes of anisotropy caused by changes in fiber orientation of unidirectional CFRP or carbon fiber prepreg can be easily and efficiently checked. Scanning detection of fiber direction and of fiber misorientation are also possible with high sensitivity. Results of measurements with successful sensitivity are shown for several kinds of unidirectional samples with artificial fiber misorientations.
