Impact Properties of Yarns Made from Different Fibers

Abstract

Yarns ranging from low tenacity and high elongation to high tenacity and low elongation were broken by impact loading and by static loading. The energy required to break each yarn under impact loading, "impact energy," and under static loading, "static energy" ; the elonga tion at break; and the tenacity were measured or calculated. The results show that the impact energy to rupture can, in general, be estimated from the static energy. The impact energy greatly exceeded the static value for yarns of low elonga tion. For yarns breaking above an elongation of about 50%, the impact energy was about equal to the static energy, except for two yarns having an elongation of over 500%, where it was less than the static value. Yarns having a very high elongation when tested at 70°F and 65% relative humidity had greatly reduced elongation when dried for 120 hrs. at 190°F and tested immediately. The elongation was still further reduced when the dried yarns were cooled for 1 hr. at — 40°F and tested immediately. These findings have a bearing on the selection of yarns for the construction of safety belts, safety ropes, and certain aeronautical textiles which may be subjected to impact loading over a wide range of temperatures.