Understanding Kevlar Deformation During Ballistic Impact Using an Integrated FBG Sensor

Abstract

Soft body armor works by dispersing impact energy across woven fibers. This dispersed impact energy is translated though the armor to the wearer, which can cause behind armor blunt trauma (BABT). Impacts from high caliber rounds can cause complex pressure states in the body, resulting in internal injury and death [1]. Current testing methods rely on using clay-backing materials to determine peak back face deformation (BFD). However, clay testing can provide only the max deformation depth and volume. There is no information on how we get to that state, how quickly the event occurs. Understanding the live dynamics of BFD formation will aid in improving both armor evaluation and the prevention of blunt force trauma. To improve soft body armor testing methods, non-invasive sensors were developed to track the back face deformation experienced during an impact event. The sensing layer developed features an imbedded Fiber Bragg grating which is used to capture strain measurements during testing. Theses strain measurements can then be used to reconstruct the peak deformation depth as it forms during impact. Testing has shown that the silicone mat and optical fiber are able to survive impacts behind armor consistently and the transient history of the BFD can be collected during impact. The maximum deformation found while testing theses sensors correlates well with independent clay indentation measurements