Relevant factors in the design of composite ballistic helmets

Abstract

In this paper, the design methodology of composite ballistic helmets has been enhanced considering biomechanical requirements by means of finite element analysis. Modern combat helmets lead to a new type of non-penetrating injury, the Behind Helmet Blunt Trauma (BHBT), generated by the deformation of the inner face of the helmet, the so-called backface deformation (BFD). Current standard testing methodologies use BFD as the main measure in ballistic testing. Nonetheless, this work discusses the relationship between this mechanical parameter and the head trauma (BHBT) by studying different head injury criteria. A numerical model consisting of a helmet and a human head is developed and validated with experimental data from literature. The consequences of non-penetrating high-speed ballistic impacts upon the human head protected by an aramid combat helmet are analysed, concluding that the existing testing methodologies fail to predict many types of head injuries. The influence of other parameters like bullet velocity or head dimensions is analysed. Usually, a single-sized helmet shell is manufactured and the different sizes are adjusted by varying the foam pad thickness. However, one of the conclusions of this work is that pad thickness is critical to avoid BHBT and must be considered in the design process.

Effect of different helmet shell configurations on the protection against head trauma

“…A human head numerical model developed from the segmentation of computed tomography (CT) images from a man belonging to the 50th percentile was employed in this work. This model was validated in previous works by Lozano-Mínguez et al 17 against low- to middle-velocity impact tests from the literature 18,19 and against ballistic experimental tests 20 on protected postmortem human surrogate (PMHS) heads. 8 The model comprises six of the main living tissues of the head: cranium (divided into the two compact bone tables and the diplöe core), facial bones, brain, cerebrospinal fluid (CSF) and scalp.…”

“…Therefore, double Figure 1. Numerical head model from Lozano-Mínguez et al 17 and Palomar et al 20 employed for ballistic simulations. precision was required both for the preprocessor and for the processor.…”

Evaluation of Combat Helmet Behavior under Blunt Impact

“…The shell is the most external part of the helmet assembly and constitutes the principal protective structure of the combat helmet. It is made of composite aramid fibers with a phenolic matrix, which is widely used in lightweight personal protection manufacturing [10,[28][29][30][31][32][33] due to its high ballistic performance and good resistance and low weight ratio. The shell areal density is 8.86 kg/cm 2 .…”

Numerical Modelling of Ballistic Impact Response at Low Velocity in Aramid Fabrics

“…The study of the physical mechanisms by which impact pressure waves reach the chest and cause injury are continuously under study in the research community. It is a goal to determine how the impact pressure waves are transmitted to the thorax or the brain in order to implement effective preventive measures and reduce the exposure risks [43,44].…”