Multi-spectral near infrared NDE of polymer composites

Near infrared signals have been used to generate images of the internal structure of fibre-reinforced polymer and foam-filled honeycomb samples. Several different measurement configurations have been investigated, including the use of both modulated light-emitting diodes at discrete wavelengths and broad bandwidth illumination for spectroscopic measurements. It is shown that transmission through the samples is wavelength-dependent, and that artificial defects can be detected within polymer composite materials. In addition, wavelength-dependent properties have been used to detect changes due to water ingress into both composite materials and a solar panel structure as a non-contact NDE technique.