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The purpose of this study was to develop material properties of human rib cortical bone using dynamic tension coupon testing. This study presents 117 human rib cortical bone coupon tests from six cadavers, three male and three female, ranging in age from 18 to 67 years old. The rib sections were taken from the anterior, lateral, and posterior regions on ribs 1 through 12 of each cadaver's rib cage. The cortical bone was isolated from each rib section with a low speed diamond saw, and milled into dog bone shaped tension coupons using a small computer numerical control machine. A high-rate servo-hydraulic Material Testing System equipped with a custom slack adaptor, to provide constant strain rates, was used to apply tension loads to failure at an average rate of 0.5 strains/sec. The elastic modulus, yield stress, yield strain, ultimate stress, ultimate strain, and strain energy density were determined from the resulting stress versus strain curves. The overall average of all cadaver data gives an elastic modulus of 13.9 GPa, a yield stress of 93.9 MPa, a yield strain of 0.883 %, an ultimate stress of 124.2 MPa, an ultimate strain of 2.7 %, and a strain energy density of 250.1 MPa-strain. For all cadavers, the plastic region of the stress versus strain curves was substantial and contributed approximately 60 strain % to the overall response and over 80 strain % in the tests with the 18 year old cadaver. The rib cortical bone becomes more brittle with increasing age, shown by an increase in the modulus (p < 0.01) and a decrease in peak strain (p < 0.01). In contrast to

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Laboratory tests in which dummy headforms are used to evaluate helmet performance must be representative of real-world conditions to ensure helmets perform well in the field. The objective of this study was to quantify shape differences that may affect helmet fit between two dummy headforms commonly used for football helmet testing. Point-cloud models of a 50th percentile male Hybrid III headform and a medium NOCSAE headform were generated using a coordinate measuring machine. The headforms were optimally aligned and shape comparisons were made in the mid-sagittal plane, three coronal planes, and 3D. Planar and 3D differences were quantified by comparing maximum (MRD) and root-mean-square (RMSD) radial deviations. Minor differences were observed in the upper skull contours of all planar cross-sections, where MRDs were less than 3.5 mm and RMSDs were less than 1.7 mm. Larger deviations were observed in other regions including the jaw in the anterior coronal plane, where the MRD was 6.6 mm and the RMSD deviation was 4.5 mm. Substantial differences were noted between the Hybrid III and NOCSAE at the base of the skull, cheeks, jaw and chin. The headforms were also compared to a head model based on medical imaging of a human subject, which the NOCSAE matched more closely than the Hybrid III. The data presented in this study show that the Hybrid III and NOCSAE headforms have substantial shape differences in several regions that are important for helmet fit, possibly making the NOCSAE a better option for realistic helmet fit.

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