Figure 6: Indentation induced damage and fracture behavior in the spike
cuticle. (A-B) SE-SEM images of cracks produced by high-load indentation
at 1000 µN in the striated region which are stopped at the outer
helicoidal region as seen both at low (A, scale bar: 20µm) and high (B,
scale bar: 5µm) high magnification. (C-D) BSE-SEM images of cracks
produced by high-load indentation at 200 µN in the highly mineralized
region observed at low (C, scale bar: 20µm) and high (D, scale bar: 5µm)
magnification. (E-F) SE-SEM images of the interface between the highly
mineralized region and the outer helicoidal region in a fractured sample
showing the deviation of the fracture plane in correspondence of the
outer helicoidal region (E, scale bar: 10µm). (F) The presence of
vertical chitin-protein fibers belonging to pore canals (arrow heads)
and bridging horizontal fibers beds is highlighted (scale bar: 5µm).
HMR: highly mineralized region; OHR: outer helicoidal region; STR:
striated region; TR: transition region. |