The objective of this study was to develop a skull model with representative features for the skull that can be scaled or morphed, based on population-based data sets for both sexes. The model was to be integrated into the VIVA+ Open Source HBM that is uniquely defined by statistical shape models to facilitate studies of population diversity. 

The model was developed in 4 steps: 1) existing literature was used to identify material modelling parameters 2) validation of the bone material models 3) head geometry for a 50%ile female head was created from a population based statistical mode. 4) simulations based on previous post-mortem human subject testing were undertaken to confirm the impact response for the head. 

The resulting head model was developed using a shell-solid-shell element configuration for the skull bones. The inner and outer cortical bone material was modelled with shell elements using LS-Dyna material model *MAT 24 (non-linear plasticity), consistent with other bones in the VIVA+ model. The trabecular core in the bone was modelled by *MAT 63 (crushable foam). A shell layer for the scalp was produced by radially extrapolating the skull geometry. Likewise, a radially inward extrapolated brain surface was created and brain tissue was modelled using solid elements. The validated model has a mass of 3.69 kg and consists of 19344 shell elements and 40434 solid elements. 

Simulations with the isolated head model to corresponding PMHS tests yielded satisfactory results depending on the area of impact and the presence of fracture. Limitations in exactly modelling the specimen and experimental conditions made exact duplication of the experimental results difficult. When local bone thickness was similar for the model and the experimental specimen, the model captured the force-time response to the point of fracture. Material failure was not included in the model and resulted in overprediction of forces and accelerations when fracture was observed in the physical specimens. 

The resulting head model for the VIVA+ HBM family provides robust and acceptable response for impact loading needed for evaluating vehicle safety systems. Its unique geometrical foundation facilitates scaling and morphing to address diversity in the population. The model has been successfully integrated in the VIVA+ model family and is available for download with the validation library.