Breaking energies of a nylon series subjected to high‐speed transverse impact

Abstract

In a study of the transient behavior of a series of nylon 6/6 yarns differing systematically in mechanical properties, the effects of high‐speed, transverse missile impact upon yarn specimens were observed by high‐speed photography. The loss in missile kinetic energy was determined directly from the reduction in missile velocity and was studied as a function of yarn tenacity and missile impact velocity. The shape of the missile energy loss curves was due to the partition of missile energy into yarn kinetic energy and yarn strain energy. The missile energy losses and yarn dynamic breaking strains were compared to static breaking energies and breaking strains for these yarns. The observed trends are discussed in terms of the differing yarn tenacities and test rates.

Effect of projectile nose geometry on the critical velocity and failure of yarn subjected to transverse impact

“…Wilde et al. 23,24 elucidated the energy loss of a projectile due to the retarding force acting on the projectile when impacting single yarns. When subjected to various levels of longitudinal pre-stress, Field and Sun 25 measured transverse wave speeds from both Kevlar® and Spectra®, which agreed with theory quite remarkably.…”

Exploration of Wave Development during Yarn Transverse Impact

“…As previously stated, there is clearly a coupled effect of increasing either the long-range failure stress or failure strain of the impacted yarn material, assuming a linear elastic response. The described plot contains iso-velocity lines for a filament material possessing a density of 1.45 g/cm 3 . Overlaid on said plot can be seen an example failure stress/strain solution of a yarn exhibiting a critical velocity of 500 m/s.…”

“…Although a rather uncommon experiment, transverse impact into single yarns has been historically used to determine baseline yarn mechanical properties, specifically to determine yarn stiffness in the longitudinal direction and the yarn critical velocity, wherein the material fails "instantly" upon projectile-yarn contact [1][2][3][4][5][6][7][8][9][10]. Such an understanding of stiffness and critical velocity is used to assess the efficacy of implementing a specific yarn material into a full body armor system; an efficacy analysis is most reasonably performed by determining the Cunniff parameter (Ω 1/3 ) [11], which is described in Equation (1),…”