EFFECTIVENESS OF THE HOMOGENEOUS SKULL MODEL UNDER BLAST WAVES

To study the mechanism of blast induced traumatic brain injury (bTBI) and design an effective protecting armor (helmet), blast responses of human head have been widely investigated via numerical studies based upon finite element modeling (FEM). In these studies, heterogeneous sandwich-like skull structure is typically simplified as a homogeneous structure, and the associated model parameter is typically obtained using three-point bending tests. In the present work, it is found that in the case of blast response of the shell-core structure, the results of the equivalent homogeneous shell with the equivalent elastic modulus extracted from three-point bending tests are greatly different from those of the heterogeneous sandwich-like shell, including the shell displacement and the core pressure of the core-shell structure: Compared with the latter, the former has a lower displacement (19%) of the front part of shell but a higher displacement (21%) of the back part of shell; the former has a lower core pressure ( ~ 15%) in the front part but a higher core pressure ( ~ 30%) in the back part. The transmission effect of stress waves propagating in the layered structure and the curvature effect of the shell might account for the aforementioned difference. Due to the similarity between the skull/brain assembly and the spherical core-shell structure (consider the skull as the outer spherical shell and the brain as the inner core), the results obtained from the spherical core-shell structure can be extended to the skull/brain assembly. Therefore, the existing homogeneous skull model constructed from three-point bending tests cannot effectively describe the blast response of the skull/brain assembly; instead, the heterogeneous sandwich-like skull model should be used in the computational model of the skull/brain assembly.