Fibrillar organic phases and their roles in rigid biological composites.

This study focused on determining the presence of organic phases in the siliceous components of rigid marine composites ("glass" sponge spicules), and thereby clarifying how such composites dissipate significant mechanical energy. Through the use of imaging by helium ion microscopy in the examination of the spicules, the organic phase that is present between the layers of hydrated silica was also detected within the silica cylinders of the composite, indicating the existence therein of a network, scaffolding, or other pattern that has not yet been determined. It was concluded that the presence of an interpenetrating network of some kind, and tenacious fibrillar interfaces are responsible for large energy dissipation in these siliceous composites by viscoelastic and other mechanical deformation processes. This discovery means that future mechanics analyses of large deformation behavior of such natural rigid composites (that may also include teeth and bones) should be based on the presence of interpenetrating phases.