Publications

Alumina-filled epoxies are composites having constituents with highly dissimilar mechanical properties, resulting in complex behavior during shock compression and release. Two distinguishing characteristics are amplitude-dependent wave structures and high release wave velocities. Recent studies examined the effects of various compositional changes on these shock properties. As expected, the strongest effects were observed when the total alumina volume fraction was reduced in steps from a nominal 43% to 0%. In the present study, compositions prepared over the same range of alumina loadings were examined at initial temperatures that were nominally -55 °C or 70 °C. Experimental configurations were identical to previous room-temperature experiments. Laser interferometry and wave timing were used to obtain transmitted wave profiles, Hugoniot states, and release wave velocities. Initial densities were determined from thermal expansion coefficients measured for each composition. Although initial density changes are very small, significant temperature effects on shock properties were observed. © 2007 American Institute of Physics.

A strong electric field can be generated when the shock-induced depoling current from a normally poled PZT 95/5 sample is passed through a large resistive load. The portion of total depoling current that is retained on the sample electrodes to account for capacitance is governed by the dynamic dielectric properties of both unshocked and shocked material. Early studies used measured load currents from single samples to assess models for dielectric response. In more recent studies, we used shock-driven circuits in which multiple PZT 95/5 elements were displaced both parallel and perpendicular to the shock motion. This allowed both load and charging currents to be measured for individual elements that are subjected to shock compression and release at different times. In the present study, these techniques have been utilized to examine dielectric properties in PZT 95/5 samples at initial temperatures from -56 to 74 °C. Significant changes in permittivity with temperature are observed in both unshocked and shocked samples. Measured currents show a complex dielectric response which can only be partially predicted using a simple dielectric relaxation model. © 2007 American Institute of Physics.

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