Application of THz radiation to polyethylene composite materials

We report on the terahertz analysis of the internal structure of ultra-high molecular weight polyethylene composite materials. The visualisation of interfaces between the perpendicularly arranged plies and the identification of stacking faults is possible because the THz refractive index depends on the orientation of fibres in the plies. Thicknesses of all plies in a composite material were determined. Moreover, the images of a delamination are presented.