Determination of mechanical properties of human skull with modal analysis

Traumatic brain injury (TBI) may happen due to loads at high rates. Due to the limitations in experimental approaches, computational methods can simulate and quantify mechanical properties. The experiments show that the human skull has nonlinear mechanical behavior and is significantly strain rate dependent. In this study, we implement Mooney-Rivlin nonlinear hyper and linear-elastic constitutive models to the experimental tensile data at different strain rates; 0.005, 0.1, 10, and 150 1/sec. A dried human skull including frontal, parietal, and occipital bones, was modeled by the 3D laser scanner and discretized by HyperMesh software to perform modal analysis using LS-Dyna finite element software. Using a roving hammer experimental modal analysis scheme, the frequency response function (FRF) and the first three natural frequencies of the skull will be measured. We found these natural frequencies are 496.9 Hz, 560.9 HZ, and 1246 Hz. Performing numerical modal analysis on the skull with pre-assumed linear elastic properties at high strain rate showed close natural frequencies as obtained by experiments. This study provides a new insight into a better understanding of the nonlinearity dynamical behavior of the human skull.