Fig. 4: Micro-CT analysis of internal GF-epoxy separation evolution in GRE composites before and after days of freeze–thaw (FT) cycling.
From: Freeze–thaw recycling for fiber–resin separation in retired wind blades
a, b 2D longitudinal and transverse cross-sections showing cracks and connected porosity, along with 3D volumetric reconstructions of their spatial networks. The untreated sample (a, blue box) displays few and unconnected cracks and pores, whereas the FT-treated sample (b, orange box) reveals a denser, wider and more continuous network of internal cracks and pores. c Spatial profiles of crack ratio and connected porosity along the specimen length (Z-direction), showing both end-region amplification and core-region degradation after FT treatment. d–g Quantitative bar plots comparing: (d) mean crack volume fraction, (e) mean crack volume, (f) connected porosity volume fraction, and (g) mean pore volume before and after FT treatment. Pictograms depict hypothesized interface degradation mechanisms supported by these results. The schematic below defines end regions (0–300, 7100–7400 µm) and core region (300–7100 µm) of tested GRE composite specimen.
