Previous work on transverse impact of single textile fibers is reviewed and extended to model orthogonal weaves in which fiber crossovers are simplified as pin. joints. A dynamic finite-element computer technique previously developed for single fibers is extended to model the woven panel, and this method is shown to produce results which are in sub stantial agreement with experimental observations of ballistic nylon panels. Impact of a woven textile panel is shown to exhibit substantial differences compared to the equivalent impact of a single fiber, primarily in that the propagating strain waves experience pervasive and complex interactions due to the influence of the fiber crossovers. The vast majority of ballistic energy is seen to be deposited in the orthogonal fibers passing through the impact point, while the other fibers are essentially ineffective, which suggests possible improvements in the design of textile structures intended for dynamic impact applications.

A number of investigators have reported on the high degree of piezoelectricity manifested by oriented films of poly(vinylidene fluoride) (PVF2). To develop applications for this piezoelectric effect, our laboratory is involved in a systematic investigation of the factors responsible for this remarkable behavior of PVF2. In a unique high‐speed process, commercial PVF2 film was uniaxially stretched to a series of draw ratios ranging up to 7/1. The resulting films were characterized by techniques involving infrared spectroscopy, density, birefringence, sonic modulus, X‐ray diffraction, and dynamic mechanical response. The films were then poled at various electric field strengths, temperatures, and times. Correlations have been made between draw ratio, physical properties, poling conditions, and piezoelectric activity of the films. It was found that the piezoelectric activity increased to limiting values with draw ratio, poling voltage, poling temperature, and poling time. It was evident that for PVF2 film a significant amount of oriented phase I crystalline material is required for high degrees of piezoelectric activity. The Appendix gives the apparent rate dependence observed for the piezoelectric effect when signal is measured with a voltage sensor of relatively low input impedance.

Single layers of nylon fabric have been subjected to high-speed missile impact at velocities ranging from 116 to 537 m/sec. The transient responses of the fabric and missile have been observed by high-speed photography. The photo graphs have shown that fabric deformation was pyramidal before penetration and more conical after penetration. The photographs have permitted measurements of the missile exit velocity from the fabric, the missile energy loss due to interaction with the fabric, the time required to penetrate the fabric, and the size and growth rate of the resultant fabric deformation cones. These results, together with a simplified mechanical model, have indicated that the broken orthogonal yarns within the deformation cone could account for 50 100% of the observed missile energy loss. In addition, during penetration of the fabric, the measured average cone-radial velocities in the fabric ranged from 50 to 80% of the values derived from fiber impact theory.

Previous experimental determinations of the E° of formation of fused metal halides have depended largely on the equilibrium cell method rather than the simpler, but less precise, decomposition potential method. This report describes a modification of the latter method, the electronic commutator method, which provides some improvements. This technique, with its simple cell and electrodes, was used to evaluate E° of formation for fused normalAgCl in the temperature range 500°–907°C in direct comparison with the equilibrium cell method. The results agree well with equilibrium cell values obtained both in this study and by other investigators.

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.