Technologies


Improving Impact Resistance in Polymers via Controlled Free Volume

Reference#: P03472


Current ballistic-resistant products on the market are mostly made by laminating polymeric material between different pieces of glass or transparent ceramics. The structure can be designed to be resistant to various ballistic threats. During impact, a bullet that hits the glass will pierce the outside layer, but the polymeric materials will absorb the energy and stop the bullet before it exits the back layer. The density and weight of these ballistic-resistant glasses are extremely high. The issues with the current ballistic laminate structure are heavy part weight, optical distortion (because of thicker parts), and high manufacturing cost.

Researchers at The Johns Hopkins University Applied Physics Laboratory have created technologies that offer more effective ballistic resistance and are greatly reduced in weight by as much as 30%, while still maintaining resistance to the current threat level. After much research, advanced armor laminate structures as well as improving the impact resistance in polymers through controlled free volume have created a more effective high-impact dissipation and a high-ballistic-resistance product with a greatly reduced density.

Advanced armor laminate is a multilayered transparent armor with alternating polymer chain orientations that are designed to further improve the ballistic-energy-dissipation and threat-arresting capabilities. Controlled molecular orientation achieved through a controlled simple shear process enables the manufacture of highly ballistic-resistant polymeric (absorber) layers for use in the armor system, which can lead to a reduction in the mass and cost of the armor system. Through tailored molecular orientation of adjacent absorber layers, the overall mass of the armor laminate can be reduced by as much as 20%; alternatively, for the same overall mass, the overall ballistic-mitigation performance can be improved. This technology uses controlled molecular orientation in adjacent layers to effectively deflect the bullet and reduce its speed. Improving the impact resistance in polymers through controlled molecular free space (MFS) improves the quasi-static and high-strain impact-fracture toughness in polymers. In the liquid state, the free volume of the polymer is large enough for the polymer chains to move easily. The chains are also able to change in conformation states. As the temperature drops below the glass transition temperature (Tg), the MFS shrinks, limiting the long-range cooperative micro-Brownian motions. The MFS below Tg is smaller than that above Tg. At temperatures greater than Tg, the MFS increases at a much faster pace than at T < Tg. High MFS allows the polymer chains to be able to compensate for large amounts of impact deformation without causing any damage to the material, thus resulting in improved ballistic resistance.

These new technologies have been fabricated and tested with the goal of producing a ballistic-resistant material that is greatly reduced in both weight and density but offers increased protection and visual acuity.

CONTACT:
Mr. K. Chao
Phone: (443) 778-7927
ott-techmanager6@jhuapl.edu