Structural Influence on the Mechanical Response of Adolescent Gottingen Porcine Cranial Bone
Technical Report,01 Apr 2015,01 May 2016
Weapons and Materials Research Directorate, US Army Research Laboratory Aberdeen Proving Ground United States
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Bone specimens were dissected from the crania of adolescent Gttingen minipigs. These specimens were small cubes that contained the entire thickness of the skull. The microstructure of these skull specimens was quantified at the micron-length scale using micro-computed tomography CT. The skull microstructure demonstrated a clear porosity dependence on location along the skull thickness the skull was highly porous near the skin-side surface and became less porous as location approached the brain-side surface. The skull specimens were then loaded in quasi-static compression to measure their mechanical response. The surface strain distribution on the specimen face was measured during loading using digital image correlation DIC. The 2-D strain field formed a gradient of iso-strain bands along the thickness depth dimension from the skin-most to brain-most sides of the skull. The specimen was modeled by discretizing the depth dimension into a series of layers. The DIC measurements were then used to derive the stress-strain response of each layer. The initial portion of this response was used to calculate depth-dependent moduli for each layer. These localized mechanical properties were related with structural parameters calculated from the high-resolution images. The model enabled the prediction of local moduli based on morphological parameters measured with CT and provided an estimation of the tissue modulus of the cranial bone.