UC San Diego

This thesis explores the structure, composition, and mechanical properties of the porcupine fish spine for the first time. The spine was found to be composed of nanocrystalline hydroxyapatite and protein that is most likely mainly type I collagen using X-ray diffraction, energy-dispersive X-ray spectroscopy, and thermogravimetric analysis. Microstructure that includes mineralized fiber sheets in the longitudinal direction and radial orientation of the sheets in the transverse direction were observed using light microscopy and electron microscopy. Mechanical properties were calculated using nanoindentation and a cantilever beam test. Finally a tapered cantilever beam model was developed and compared to that of a uniform cantilever beam. The tapered beam model showed that while the stresses experienced were similar, the location of the maximums stress in the beam is near the tip of the beam rather than the base.