The role of local material properties in modeling fracture tolerance of the human thorax

This dissertation presents the results of dynamic material tests and computational modeling exploring the effects of regional rib mechanical properties on thoracic fracture patterns. Test coupon modeling was used to verify the test setup. These material properties were incorporated into a human body computational model. The data from the material tests for all subjects indicate a statistically significant increase in the average stiffness and average ultimate stress for the cortical bone specimens located in the lateral portion of the ribs (11.9 GPa modulus, 153.5 MPa ultimate stress) versus the anterior (7.51 GPa, 116.7 MPa) and posterior (10.7 GPa, 127.7 MPa) rib locations. The results from computational modeling for both frontal and lateral impacts illustrate that the location and number of rib fractures are altered by the inclusion of rib material properties that vary by region. A sensitivity analysis of the effects of altering the failure strain criteria on the number of rib fractures predicted is performed revealing improved sensitivity of the modified THUMS model versus the original THUMS model for failure strains from 0.8 to 1.8%. The results from the small specimen tests are compared to results obtained for three-point bending of whole human rib sections.