Investigation of glass–fibre reinforced polymers by polarisation-sensitive, ultra-high resolution optical coherence tomography: Internal structures, defects and stress

In this paper, we report on optical coherence tomography (OCT) for the investigation of glass–fibre reinforced polymer (GFRP) materials. OCT, a contactless and non-destructive imaging technique, provides depth-resolved information on internal structures within semi-transparent materials. In our study, we apply a highly advanced OCT technique: we use a transversal scanning, ultra-high resolution, polarisation-sensitive (UHR-PS)-OCT for the analysis of various GFRP samples. UHR-imaging with resolution in the micron range is shown to provide information on the scale of single fibres. PS-OCT, an extension of classical OCT, is sensitive to birefringence and consequently to anisotropies and stress within a material. Our system is therefore applied to the investigation of defects located within the fibre layers of loaded and damaged GFRP samples. Imaging of matrix fracture, cracks, and internal stress, demonstrates the high potential of UHR-PS-OCT for the investigation of damage in GFRP materials, with special emphasis on detecting the early stages of defect formation.