Flexural deformation and fracture behaviors of the sandwich turtle rib bones with hierarchical woven fibers

Abstract

Turtle rib is a kind of bio-composites with excellent fracture resistance and toughness, whose composition and structure were characterized by X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM), which indicated that the turtle rib has woven hierarchical fibrous and sandwich structure. With the aid of acoustic emission (AE), bi-spectrum estimation analysis and Wavelet, the damage behaviors during the flexural fracture process of the ribs can be summarized as three categories: breakage of the mineralized collagen fibers, collagen fiber debonding and organic matrix failure. Sandwich specimens have higher proportions of fiber debonding AE signals, which is consistent with the hierarchical fracture morphology. The AE signal distributions implied that the fracture dynamics of turtle rib bones drive the materials into a self-organized criticality (SOC). The woven hierarchical fibrous and sandwich structure can delay the damage avalanches, certainly making a contribution to the ribs' fracture toughness.