Quantitative comparison of optical transmission scanning with conventional techniques for NDE of impact damage in GFRP composites

Robust and quantitative non-destructive evaluation (NDE) is essential for damage characterization in advanced materials, such as glass fiber reinforced polymer (GFRP) composites. Previous work demonstrated the capabilities of an optical transmission scanning (OTS) system, including an advanced image processing algorithm, for rapid and non-contact NDE of healthy and impacted GFRP samples. The number of delaminations and their contours in the test samples were accurately identified. In this paper, damage was introduced in GFRP samples by low velocity impacts of different energies, and OTS was validated by comparing the inspection results with conventional NDE techniques, including pulse-echo ultrasonic testing (UT) and UV dye penetrant testing (UV DPT). In addition, quantitative comparisons of damage severity were made for OT scans and UT C-scans by converting images to a normalized damage metric. Experimental results demonstrated that the estimated extent of impact damage agreed very well for all used techniques. Thus, OTS combines the cost-effectiveness and rapidity of qualitative techniques (e.g., UV DPT) with the more robust and comprehensive data analysis provided by quantitative methods (e.g., UT).