Enhancing Helmet Capabilities Against Ballistic Threats via Physics-Based Injury Prediction
Abstract
Approved for Public Release-Protecting a warfighter s head from injury is critical to survivability. Conventionally, combat helmets have been-used to protect against ballistic threats and shrapnel, thereby reducing head injury and fatalities. However, the-relation of the helmet shell material, in concert with the helmet liner material, to brain injury risk assessment-remains largely unknown. Head injury from projectiles that do not penetrate the helmet is commonly labeled Behind-Helmet Blunt Trauma (BHBT). It is often attributed to the deformation of the inner face of the helmet, called-backface deformation (BFD). At the same time, BFD requirements for ballistic testing and its relation to BHBT are-not well understood, nor is BFD a universally accepted metric for helmet performance. Consequently, there is an-urgent demand for research that will direct the design and testing of head protection systems to prevent-ballistic helmet penetration and deformation injuries.-Traditionally, the ballistic performance of a material is described by its ballistic limit, defined as a specific-projectile velocity that penetrates the material approximately 50% of the time. Additionally, when a bullet-impacts a helmet, a cone is formed on the helmet s back face. The depth of this conical budge, known as a-backface signature, should not exceed a critical value. It is assumed that when that critical value is reached,-the helmet shell can strike the skull causing BHBT. Notably, neither of these metrics (ballistic limit nor-conical budge) gets directly at the underlying deformation and failure mechanisms that cause helmet material-damage and dictate energy absorption. Thus, they are challenging to use as the basis for next-generation helmet-design when changing materials and geometries.-Over the years, attempts have been made to improve the effectiveness of combat helmets. Specifically, composite-shells replaced heavy metallic shells, offering better strength-to-weight ratios. However, despite increased-penetration resistance, the occurrence of large deformations of the composite shells increases the probability of-BHBT. The work in this proposal will explore the role of ballistic helmet shell and liner materials both-experimentally and computationally to understand the coupling of four factors on the ballistic performance of the-helmet: helmet to head standoff distance, foam liner plateau stress, shell material and helmet testing methods-via surrogate head models. Additionally, this work will take the results from the helmet investigations and link-them to risk of injury risk through a high fidelity computational head model. Overall, the proposal consists of 4-aims:-1. Characterize and model helmet shell composites-a. Through FEA simulation, the response of a helmet-shell/liner assembly under ballistic loadings will be-simulated and assessed, providing a digital helmet design tool that can reduce the time of the iterative design,-build, test cycle.-b. Experiments will characterize relevant dynamic deformation and failure behavior of helmet shell composites-to provide predictive input parameters for the model-2. Create a ballistic helmet deformation test that is connected to injury and survivability we will give-helmet designers and standards developers a framework to evaluate how well a ballistic helmet performs in-preventing injury and death-3. Conduct simulation-based parametric studies to assess shell material, standoff and liner (pad) material.-Understanding the coupling and interplay between key parameters in helmet design will ensure that protection is-optimized for preventing injuries.-4. Quantify human injury risk under ballistic impact to the helmet. This study will extend the functionality-of our FE injury models to include the assessment of head injury risk from ballistic threats.--This proposal does not include any human or animal use.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 08, 2024
- Source ID
- N000142412118
Entities
People
- Christian Franck
Organizations
- Office of Naval Research
- United States Navy
- University of Wisconsin System