# Evaluation of Combat Helmet Behavior under Blunt Impact
## 5 Conclusions  
In summary, the current study examined how changes in the head model could lead to differences in traumatic brain injury (TBI) under blunt impact conditions. Two head models were used, i.e., a standardized head surrogate by the ECE R22.05 standard and a realistic human head model. To observe the influence of the impact zone on the degree of injury induced to the wearer, drop impacts were carried out at the following four locations: front, top, rear, and side. Peak linear acceleration, HIC, and AIS scale level were used to analyze the TBI.  
The differences in the results between the human head and head surrogate configurations may be due to various reasons, for example, head mass and geometry. In this study, the human head model used was obtained for a real person; however, the head surrogate was imposed by motorcycle helmet standards. For these reasons, the human head results are slightly higher than the experimental and head surrogate results.  
Regarding compliance with regulations, complying with the limits established by the ECE R22/05 standard does not exempt the user from suffering injuries from low impact velocity, such as falls or blows, which are not severe but are harmful and cause TBI.  
Figure 13: PLA at different frontal impact velocities for the human head.  
Followed by analyzing the peak linear acceleration and HIC (this last one according to the ECE R22/05 standard and the NHTSA regulation), the restrictions imposed by the regulations are satisfied in practically all cases for the head surrogate model. However, for the human head model, it complies with the criteria imposed by European Regulations regarding acceleration and HIC (\(<\)2400), but not in the case of the NHTSA standard, because it is higher in all impact locations than HIC 1000. With regard to anvil geometry, a change in the morphology of the impact surface does not generate large variations in TBI.  
Therefore, the current configuration of a combat helmet does not provide high drop performance. The standards applied are especially designed for motorbike helmets. Consequently, to improve the impact performance of current combat helmets, their configuration should be modified. Foam pads may have an important role to play in future research for reducing brain injury rates.  
Conceptualization, J.A.L., A.O., and M.R.M.; methodology, C.M.-G., M.R.M., and I.R.; simulations, C.M.-G. and J.A.-M.; experimental data, A.O; investigation, J.A.-M., C.M.-G., and M.R.M.; writing--review and editing J.A.-M., J.A.L., A.O., C.M.-G., I.R., and M.R.M.; supervision, J.A.L, M.R.M. and J.A.-M.; funding acquisition, M.R.M. All authors have read and agreed to the published version of the manuscript.  
This work has been carried out within the framework of the research project DPI2017-88166-R of the FEDER program financed by the Ministerio de Economia, Industria y Competitividad and the Spanish Ministry of Education, Culture and Sports for the professor's mobility program [PERSON]'s 2018 grant (CAS18/00292).  
The authors acknowledge the Ministry of Economy and Competitiveness of Spain and the FEDER program under the Project DPI2017-88166-R for their financial support of this work and the Spanish Ministry of Education, Culture, and Sports for the professor's mobility program [PERSON]'s 2018 grant (CAS18/00292). The authors also acknowledge the FECSA for the experimental data. The authors declare no conflict of interest.