A body armor panel consisting of twelve identical layers of 2 X 2 basket weave nylon fabric was investigated after impact by a fragment simulator .22-caliber steel missile in the range of 330-420 m. sec. (1100-1400 ft. sec.) striking velocities. The kinetic energy of the projectile was either slightly higher or lower than that the panel could absorb (706,000 g.-cm.).Completely and partially penetrated holes were investigated. The area surrounding the bullet holes was studied to learn about the various types of deformations and damages in each layer. The microscopic observations were obtained at various magnifications (5, 10, and 200 X) from cross sections of the panel and from individual layers removed from the panel.Cross sections at various levels were made in three directions, either perpendicular or parallel to the panel surface. In these sections the distortion of the fabric pattern, alignment of extended, unravelted. and broken yarns into the direction of bullet movement, compression of yarns, softening, heat relaxation, fusion, decomposition, and fibrillation of nylon filaments were observed. It was recognized that the permanent damage was localized to a small area close to the path of the fast-moving missile.After separating the panel into individual layers, the stoppage of the projectile was studied. A slight dissipation of the stress was observed in those layers which were exposed to the bullet after it was stowed down. Some damages to nylon filaments were caused by the transient and localized heat generated during the impact of the missile.Fibrillation indicates the vigorous movements of filaments which took place in the panel during penetration. The restriction of permanent deformations and defects to small regions was explained by the presence of cross yarns. They prevent the propagation oi the stress from the impacted spot to any considerable length along the yarns.

The recovery data available on textile materials are scarce and difficult to compare. Very few data on fibers have been presented in which differentiation is made between immediate and delayed recovery. Until the present, no adequate method except the pulse-propagation technique has been known to separate these strain components. Using the Instron tensile tester, a cycling method was developed to measure directly the total elongation and permanent set and to permit also determination of the immediate and delayed recovery. The conditions of the tests were standardized. Some studies were made on the effect of deviations from the standardized conditions.The recovery behavior of 25 samples representing 16 different textile fibers was measured under the standardized conditions. Their recovery behavior is presented by tabular data and by two series of rectangular graphs. The values of immediate and delayed recovery and of permanent set as obtained describe the recovery behavior of fibers with adequate accuracy from the initial application of stress to the breaking point.

In the presence of gelatine, sucrose crystallizes after a relatively short time (minutes, hours) when exposed to the radiation of an x-ray tube with copper target, or of a medical microwave unit. The formation of sucrose spherulites, visible with the naked eye, was observed.

The x-ray powder pattern is used for the identification of organic dyestuffs by comparison with standard samples. A discussion is given of the difficulties arising from polymorphism and the sensitivity and limitation of the method. Application of this technique to various dyestuffs and to difficult problems of dyestuff chemistry is described. The x-ray analysis is compared with methods such as chemical identification, dye tests, and heated specimen microscopy.

The inherent abrasion behavior of 14 different textile materials in the form of yarns was investigated. Abrasion was expressed by the abrasion damage, which is the opposite of abra sion resistance. Abrasion damage was measured quantitatively by the fiber fineness (grex) destroyed in flexing around a steel bar under standardized conditions using the Stoll-Quarter master abrasion tester. The abrasion damages were evaluated relative to that of high-tenacity nylon multifilaments. Great differences exist in the abrasion behavior of various textile fibers. The damage of multifilaments increases from nylon to Dacron polyester fiber, viscose, Fortisan, Orlon acrylic fiber, Saran, silk, acetate, and casein, while that of staple yarns increases from nylon to Dacron polyester fiber, cotton, Fibravyl, Dynel, Kuralon, Thermovyl, wool, Orlon acrylic fiber, viscose, and acetate. Staple yarns were always more abraded than corresponding multifilaments. Although high elastic energy of fibers is the main factor preventing inherent abrasion damage, extensibility, yarn surface, and friction must also be taken into account in interpreting the abrasion behavior of various textile fibers.