Ageing of High Strength p-Aramid Fibers Used in Body Armor

To improve the reliability and design of armor, it is imperative to understand the failure modes and the degradation rates of the materials used in armor. Despite the best efforts of manufacturers, some vulnerability of armor materials to ageing due to hydrolytic or oxidative environments is expected and may result in the degradation of material properties such as tensile strength. In this work, p-aramid yarns from two manufacturers were exposed to environmental conditions of various fixed temperature and humidity combinations. The maximum temperature and humidity condition was 70 °C and 76 % RH. Tensile tests were performed on specimens extracted at several different timepoints over the course of at least one year to determine the change in ultimate tensile strength and failure strain as a function of time, temperature, and humidity. These materials were found to be generally resistant to degradation at most conditions, showing changes of less than 10 % only at the highest temperature and humidity conditions.