Ballistic impact resistance of graphite composites with superelastic SMA and Spectra hybrid components

Abstract

The effect of adding small amounts of high strain hybrid components on the impact resistance of graphite epoxy composites subjected to projectiles traveling at ballistic velocities (greater than 900 ft/sec) has been studied. The hybrid components tested include superelastic shape memory alloy (SMA) and a high performance extended chain polyethylene (ECPE) known as Spectra™. From testing 1.2% volume fraction superelastic SMA fiber layers embedded on the specimens front, middle, and backface, it was concluded that the backface was the most suitable location for a high strain hybrid component since the hybrid component is not restricted from straining by surrounding graphite material. However, no significant increases in energy absorption were found when two perpendicular SMA layers were tested on the backface. In all cases, the embedded SMA fibers were pulled through the graphite without straining to their full potential. It is believed that this is due to high strain rate effects coupled with a strain mismatch between the tough SMA and the brittle epoxy resin. However, a significant increase in energy absorption was found by adding ECPE and ECPE/SMA layers to the backface of the composite. With a 12% increase in total composite mass, a 99% increase in energy absorption was observed.