Polymer foams serve an important role in the assessment and certification of stab resistant body armor for both US and UK standards. A composite of neoprene and polyethylene foam is used behind the armor during testing. The foam mimics stab dynamics by shaping the force-displacement curve at impact. In addition, polyethylene foam is used as a damping material in the drop mass. The foam properties, thickness, density, hardness, are specified by the stab standards. However, foam suppliers have changed since the original selection of the foam composite materials and this has posed supply challenges for certification laboratories. It has been difficult to obtain foam that meets both the density and thickness criteria specified in the standard; therefore testing laboratories must rely on a resilience test to qualify new foam materials. The resilience test may not have sufficient resolution to determine the effect of structural differences on impact response. In this research, the deformation behavior of four different individual foam layers and two stab packs was measured by uniaxial compression. Foam energy absorption was quantified using efficiency and ideality parameters that were calculated from stress-strain curves at low strain rates. These parameters highlighted differences between foams as a function of physical properties and compressive stress. Efficiency curves were related to the three levels of impact energy specified in the stab standards. Efficiency and ideality highlighted the serial deformation behavior of stab packs subjected to uniaxial compression. This energy absorption methodology has the potential to improve current foam certification methods to provide standard foam materials for armor certification.
Proceedings Title: PASS 2010 Proceedings
Conference Dates: September 13-17, 2010
Conference Location: Quebec City, -1
Conference Title: Personal Armour Systems Symposium
Pub Type: Conferences
foam, energy absorption, stab testing