A ballistic laboratory was designed and built to accommodate the impact of . Kevlar® woven fabric of varying ply levels, while manipulating the geometrical shape, weight, and impact velocity of the projectile. A chronograph system was used to measure the striking and residual velocities of the missile. Empirical relations were determined between the experimental data and the quantity 1/√L, where L is the ogive length of the projectile. This quantity was found to be useful in characterizing projectile geometrical effects on the impact performance of woven fabric systems. The effects of projectile shape on the number of fabric plies, velocity loss data, and thus V50 values are characterized by the empirical relations.

In this paper we consider the wide-angle x-ray diffraction patterns of several nylon 66-polyethylene glycol (PEG) blend fibers before and after aqueous extraction. Antistatic additives such as PEG are frequently found in polyamide fibers. The patent literature indicates, however, that fiber blend systems of this type must be extracted in order to function effectively as antistatic fibers.'**The fibers examined in this study were prepared by an industrial laboratory by melt spinning mixtures of PEG and nylon 66 polymer chip. The samples ranged in composition from 0-20% PEG by weight in increments of 5%. The PEG had a molecular weight of ca. 20,000 (Union Carbide Corporation's polyethylene glycol compound 20M). After melt spinning, each blend was drawn to the same draw ratio of approximately 5X. Samples of each blend were extracted in an aqueous solution containing 10 ghiter of Oryus-AB detergent (Proctor and Gamble) for 3 hr at 7OoC and then dried in hot air at 7OoC for 2 hr. All samples containing PEG additive show a significant increase in electrical cond~ctivity.~The wide-angle pattern of the 100% unextracted nylon 66 fiber sample is shown in Figure 1. This structure has been completely analyzed by Bunn and Gardner.' The x-ray pattern of extracted samples of nylon 66 is practically unchanged except the major reflection peaks on the equator are somewhat sharper. The extraction process induces changes approximately equivalent to an annealing treatment of 200OC for 1 min.

A single measurement of twist is insufficient to typify open-end yarns because the twist (tpi) of the fibers comprising the yarn core is different from those comprising the outer sheath, and both are usually lower than the machine value. The differences may be expressed in terms of a twist gradient which is a function of machine design, operating conditions, and fiber characteristics. In these experiments the differences were particularly marked with high polyester blends.

A review of the literature and extensive field interviews have been conducted on the subject of needle heating in high-speed sewing. As a result of this investigation, a survey of the current state of the art and knowledge available in the field has been completed and is presented in the following categories: (1) the nature of the problem and the difficulties which arise in commercial operations; (2) quantitative methods of measuring needle temperatures; (3) the influence of machine factors such as sewing speed, length of sewing time, and needle design on the heat generated during sewing; (4) the influence of material factors such as fabric structure and finish, layers of fabric, and sewing thread on needle heating; (5) techniques for alleviating needle heating problems; and (6) the mechanism of generation and dissipation of heat in the sewing process. Some heretofore unpublished data are presented.

The nature of the forces involved when a sewing needle penetrates a fabric have been studied on an Instron in an attempt to identify some of the factors which influence the needle-fabric interaction leading to heat generation. The measurements were made at velocities three to four orders of magnitude lower than actual sewing velocities. Four major variables considered were needle velocity, needle diameter, needle surface finish, and number of fabric layers. The influence of these factors on the maximum penetration force and on the energy required to drive the needle into and out of fabric has been studied. All these factors and their interactions (except needle velocity in some cases) affect the maxi mum penetration force of the needle and the energy of penetration. The effect of needle velocity over the range covered, even when significant, was minor (of the order of about 10%). The needle diameter affects the maximum penetration force and energy of penetration to a much greater extent. They are found to increase at a greater than linear rate with in creasing needle diameter. In one fabric, these parameters increased with the third or fourth power of the diameter. Whereas certain special high-emissivity needle-surface finishes have been found to reduce temperatures of needles during sewing, more energy is expended when these needles pass through fabrics than is expended with regular-finished needles. In a series of exploratory experiments, no differences in behavior were observed for a variety of needle-point shapes (twist point, diamond point, and standard ball point) or for tests using sewing threads compared with tests made without sewing threads. The bulged eye needle was effective in reducing energy buildup, compared with ball-point needles. The maximum penetration force and energy of penetration were found to increase linearly with increasing numbers of fabric layers. Wherever feasible, attempts are made to relate observed penetration energy measurements with expected needle heating characteristics and with results reported in the literature.