| Popis: |
Polyurea is a microphase-separated block copolymer that exhibits unique properties as a result of its phase-separated morphology. Experimental results suggest and computational simulations support that judicious arrangement of steel and polyurea can enhance shock mitigation. Schlieren imaging techniques can be used to qualitatively investigate the behavior of shock waves. The properties and performance of polyurea can be significantly modified by the integration of additives, and micromechanical modeling can aid in the design of such composites with specific properties. For polymers and their composites, temperature, pressure, and strain rate usually affect the mechanical properties of the material at the same time. However, direct measurements of the mechanical properties for the high-rate loadings are often difficult to perform. Thus, alternative methods are used to predict and estimate the mechanical properties. Full-scale head–neck manikins were fabricated in order to assess comparative intracranial pressure and acceleration from explosive blast. A range of standoffs to the explosive were used. Three helmet variations were examined: the standard advanced combat helmet (ACH), an ACH helmet with a polymer coating, and a standard World War II, M1 helmet. Use of a helmet decreased the pressure at different locations within the brain. All of the helmets resulted in similar peak pressure and resultant acceleration values. However, the ACH helmet with a polymer coating decreased the time of pressure application significantly, lowering the applied impulse at the closest standoffs. The lower impulse would also contribute to a decrease in applied power density in these portions of the brain. Use of a polymer coating provides a basis to explore other helmet variations to provide protection from traumatic brain injury. |
