Strain-rate dependence of plastic bonded explosives at rates beyond 1000 /s

Predicting the strength and integrity of components utilizing plastic bonded explosives (PBX) requires a fundamental understanding of the strength and rate sensitivity of these materials under various thermal and mechanical insults. These conditions include extreme loading rates and thermal cycling. In the past, PBX materials have been well characterized under creep to low-rates (0.00001 - 0.01 /s) and dynamic loading rates of about 1000 /s. However, data for understanding and quantifying rate sensitivity at rates beyond 1000 /s is lacking, therefore, our understanding of the strength of unconfined PBXs at high rates has suffered from this lack of data. In this work, we present results from a series of miniature Kolsky bar experiments on PBX 9501 and 9502. The results reveal the strength under uniaxial stress conditions at rates of up to 10,000 /s. In comparison with the literature (i.e., measurements made between 0.00001 - 0.01 /s), our results show remarkabely higher than anticipated rate-sensitivity for both materials, suggesting a transition in the rate governing mechanism. The transition rate for these materials and a potential explanation for these effects will be discussed.