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Abstract. This paper addresses the modeling of certain rate-dependent mechanisms which contribute to hysteresis inherent to piezoelectric materials operating at low frequencies. While quasistatic models are suitable for initial material characterization in some applications, the reduction in coercive field and polarization values which occur as frequencies increase must be accommodated to achieve the full capabilities of the materials. The model employed here quantifies the hysteresis in two steps. In the first, anhysteretic polarization switching is modeled through the application of Boltzmann principles to balance the electrostatic and thermal energy. Hysteresis is then incorporated through the quantification of energy required to translate and bend domain walls pinned at inclusions inherent to the materials. The performance of the model is illustrated through a fit to low frequency data (0.1 Hz -1 Hz) from a PZT5A wafer.

We investigated the chemical, mechanical and geometrical properties of basalt fibers from three different commercial manufacturers and compared the results with those from an industry standard glass fiber. The chemical composition of the fibers was investigated by X-ray fluorescence spectrometry, which showed that basalt and glass fibers have a similar elemental composition, with the main difference being variations in the concentrations of primary elements. A significant correlation between the ceramic content of basalt and its tensile properties was demonstrated, with a primary dependence on the Al2O3 content. Single fiber tensile tests at various lengths and two-way ANOVA revealed that the tensile strength and modulus were highly dependent on fiber length, with a minor dependence on the manufacturer. The results showed that basalt has a higher tensile strength, but a comparable modulus, to E-Glass. Considerable improvements in the quality of manufacturing basalt fibers over a three-year period were demonstrated through geometrical analysis, showing a reduction in the standard deviation of the fiber diameter from 1.33 to 0.61, comparable with that of glass fibers at 0.67. Testing of single basalt fibers with diameters of 13 and 17 µm indicated that the tensile strength and modulus were independent of diameter after an improvement in the consistency of fiber diameter, in line with that of glass fibers.

Typical soft armor systems are constructed of multiple layers of a single fabric type. This empirical research sought to begin optimization of these systems through hybridization, sequencing dissimilar armor fabrics to maximize their ballistic protective performance, by first investigating single plies with a spectrum of properties to determine their behavior and response to impact. Eight individual plain weave fabrics with varying yarns and thread counts were manufactured from para-aramid and ultra-high molecular weight polyethylene (UHMWPE) yarns and physical and ballistic characterizations were conducted. The ballistic impact tests established the specific energy absorption (SEA) of each fabric across a range of impact velocities (340–620 m·s–1) and the transverse displacement wave velocity across the rear of the fabric was found using digital image correlation. Low cover factor ( Cfab) fabrics (0.74–0.84) consistently showed faster transverse wave speed than the high Cfab fabrics (0.84–0.96) for any given yarn type. The relative SEA of the fabrics varied dependent on both the impact velocity and number of plies impacted. It was found that lower Cfab fabrics had the highest SEA, critical velocity and transverse wave velocity. UHMWPE fabrics were not considered suitable for a woven hybrid system as they had a significantly lower SEA compared to all the para-aramid fabrics. Results indicate that a hybrid system, when considered as a theoretical spaced system, would benefit from higher Cfab fabrics as rearward layers. However, transverse wave results suggest the lower response of these fabrics may inhibit lower Cfab fabrics at the front of a combined hybridized system.

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