The objective of this study was to evaluate the effects of sex, loading rate, and age on the compressive and tensile material properties of human costal cartilage over a wide range of subject ages and sexes. Cylindrical compression samples and dog-bone shaped tension samples were tested to failure on a material testing system using target strain rates of 0.005 strain/s and 0.5 strain/s. Compression data were obtained from forty (n = 40) subjects (M = 26, F = 14) ranging in age from 11 – 69 years (Avg. = 39.1 ± 18.2 yrs.), and matched loading rate data were obtained for thirty-four (n = 34) samples. Tension data were obtained from forty-one (n = 41) subjects (M = 30, F = 11) ranging in age from 10 – 59 years (Avg. = 32.9 ± 14.9 yrs.), and matched loading rate data were obtained for seventeen (n = 17) samples. For both compression and tension, load and sample deflection data were collected and used to calculate stress and strain. For the compression data, the toe region was fit using a second-order polynomial, and the toe transition stress, toe transition strain, second-order polynomial coefficient A, and second-order polynomial coefficient B were calculated. In addition, the elastic modulus, ultimate stress, ultimate strain, and strain energy density (SED) were also calculated for each test. For the tension data, only the elastic modulus, ultimate stress, ultimate strain, and SED were calculated for each test. There were no effects of sex on the material properties for either method of loading or strain rate. Therefore, male and female data were combined for the age and loading rate analyses. For compression, toe transition stress, toe transition strain, A, elastic modulus, ultimate stress, and SED were all found to be significantly higher at 0.5 strain/s compared to 0.005 strain/s. For tension, no material properties were found to differ with respect to loading rate. Regarding the effects of age, toe transition stress, toe transition strain, A, B, ultimate stress, ultimate strain and SED were found to significantly decrease with advancing age for the 0.005 strain/s compression data. At 0.5 strain/s, toe transition stress, toe transition strain, elastic modulus, ultimate stress, ultimate strain, and SED all significantly decreased with advancing age. For tension, ultimate stress, ultimate strain, and SED were found to significantly decrease with advancing age at 0.005 strain/s and 0.5 strain/s. Comparing the two loading modes, the ultimate stress, elastic modulus, and SED were significantly higher in compression than in tension. For the compression samples, sample density and percent calcification were also obtained for each sample using physical measurements and micro-CT scans, respectively. However, since there were only a few samples with large calcifications, no meaningful trends were found. This is the first study of its kind to analyze the effects of sex, loading rate, and age on both the compressive and tensile material properties on human costal cartilage from such a wide range of subject ages. The results from this study can be used to develop more accurate finite element models of the human body, which will allow researchers to better evaluate human occupant response and injury risk in motor vehicle collisions for both young and old individuals. / Master of Science / Serious thorax injuries are often observed in motor vehicle collisions. Although a considerable amount of research has investigated the material and structural properties of rib cortical bone and whole rib sections, only a limited number of studies have focused on characterizing the material properties of costal cartilage, which comprises a substantial portion of the anterior region of the thorax. The studies that do exist include small subject pools and/or are limited to sub-failure indentation tests. Indentation tests are limited to low deflections and focal loading and are unable to obtain the failure material properties of costal cartilage. Therefore, the purpose of this study was to quantify the compressive and tensile material properties of human costal cartilage at two loading rates for a wide range of subject demographics. These properties were then evaluated with respect to sex, loading rate, and age. Cylindrical compression samples and dog-bone shaped tension samples were tested to failure on a material testing system at target strain rates of 0.005 strain/s and 0.5 strain/s. Compression data were obtained from forty (n = 40) subjects ranging in age from 11 – 69 years, and tension data were obtained from twenty-eight (n = 28) subjects ranging in age from 10 – 59 years. For both compression and tension, load and sample deflection data were collected and used to calculate stress and strain. For the compression data, the magnitude and shape of the initial loading region (i.e., the toe region), elastic modulus, ultimate stress, ultimate strain, and strain energy density (SED) were quantified for each test. For the tension data, the elastic modulus, ultimate stress, ultimate strain, and SED were calculated for each test. There were no significant effects of sex on the material properties for either method of loading or strain rate. Therefore, male and female data were combined for the age and loading rate analyses. For compression, the toe region transition point (i.e., stress and strain), toe region shape coefficient A, elastic modulus, ultimate stress, and SED were all found to be significantly higher at 0.5 strain/s compared to 0.005 strain/s. For tension, no material properties were found to differ with respect to loading rate. Regarding the effects of age, toe region transition point (i.e., stress and strain), toe region shape coefficients A and B, ultimate stress, ultimate strain, and SED were found to significantly decrease with advancing age for the 0.005 strain/s compression data. For the 0.5 strain/s compression data, toe transition stress, toe transition strain, elastic modulus, ultimate stress, ultimate strain, and SED all significantly decreased with age. For tension, ultimate stress, ultimate strain, and SED were found to significantly decrease with advancing age at 0.005 strain/s and 0.5 strain/s. The ultimate stress, elastic modulus, and SED were higher in compression than in tension. Overall, this is the first study to evaluate the effects of sex, loading rate and age on the compressive and tensile material properties of human costal cartilage from a wide range of ages. These data can be used to assess differences in the response and tolerance of the human rib cage for occupants of various age in motor vehicle collisions.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/115593 |
| Date | 08 July 2022 |
| Creators | Nowinski, Hannah Marie |
| Contributors | Department of Biomedical Engineering and Mechanics, Kemper, Andrew R., Hardy, Warren Nelson, Albert, Devon Lee, Agnew, Amanda M. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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