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 Spectram. 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.

This paper presents a model that can be implemented to quickly estimate the resistive heating and the resulting transient temperature response. Quantifying the energy deposited in the rails and implementing an effective thermal management system will be key elements of an effective design for a large-scale electromagnetic launcher. The total current was divided between the inside, upper/lower and outside surface based on the results of a current distribution calculation. The diffusion of the magnetic field into each surface was modeled in order to determine the current distribution and the resistive heating. Cooling between shots was taken into account by solving the one dimensional transient heat diffusion equation within each surface. Repeating these calculations for a number of discrete segments down the length of the rail enabled the prediction of the total resistive rail heating and the temperature profile along the length of the rail. Experimental tests were conducted that verify the presence of localized heating in the corners of a U-shape conductor made of 7075 Aluminum. Taking into account the localized resistive heating near the surface of the conductor will become increasingly important with large-scale guns.

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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.