Measurement of partition of stress between mineral and collagen phases in bone using X-ray diffraction techniques

The aim of this study was to present clear evidence of a stress concentration in bone as a two-phase composite of a collagen matrix reinforced by hydroxyapatite (HAP) mineral particles. X-ray diffractometry was performed on cortical bone from a bovine femur in order to measure strain in HAP along the c-axis as a response to a macroscopically applied force. From the obtained strain of HAP, the stress applied to HAP particles was determined by using Youngʹs modulus value of HAP in the literature. Dividing the stress of HAP by that macroscopically applied to a bone specimen, the stress concentration coefficient, χH, was estimated. Using the Hirsch equation with the estimated χH value, mineral content of bone was estimated, which accords with the mineral content values of bone in the literature.