Some Mechanical Properties of Kevlar and Other Heat Resistant, Nonflammable Fibers, Yarns and Fabrics

The results of the first year's work under this contract are reported in full in AFML-TR-74-65, Parts I and II, and are only summarized herein. Results of the second year's work are described in full. The tensile properties of wet Kevlar yarns were measured at 70 and 190 F, as well as the response of Kevlar 29 yarn to low speed tensile strain cycling at 70 and 400 F. Torsional stress-strain behavior of Kevlar fibers and yarns was studied extensively, including the effect of elevated temperature exposure on this behavior. The bending recovery of Kevlar filaments was measured for different imposed curvatures and different times under strain. The effect of exposure to elevated temperature or bending recovery was investigated, and some deductions made concerning the behavior of these fibers in compression, particularly in respect to the existence of compressive yield. Preliminary measurements of the tensile properties of Durette and HT-4 fabrics under radiant heat flux were made, and the value of such measurements discussed. Finally, the morphology of Kevlar 49 fibers subjected to various types of mechanical working was examined using a scanning electron microscope.
See also report dated May 1974, ADB002047.