Figure 4.

(a) 3D AFM topographic image of a fully degraded fibre, located at the extreme edge of the sample; (b) face C investigated through AFM-PF-QNM; black and red circles indicate the fibres selected for AFM measurements; (c–e) are AFM topographic images of edge, middle and core areas, respectively, and (f–h) the corresponding indentation modulus maps. (i) shows the indentation modulus distribution for each investigated region, indicated in white dotted lines in (f–h). In (f), no data were recorded in the hatched area.