Shockwave Compression of Organics and Shock-Induced Chemistry

Research in DE-9 is largely focused on understanding materials physics and chemistry under the extreme conditions produced under shock loading, either by impact or high-explosive drive. Organic materials (e.g., polymers, liquids, reactive materials) can display rich behaviors under these conditions, which include such phenomena as

• highly non-linear compressibilities,
• viscoelasticity,
• compaction of porosity or filler particle contact,
• numerous chemical reactions,
• shock-to-detonation transitions,
• melting, and
• reactants-to-products evolution.

Current research thrusts include shock loading and equation-of-state development for polymers and polymeric composites, as well as investigation of initiation thresholds and mechanisms. Other efforts involve the development of "Pop-plots" for liquid explosives, interrogation of shock-induced chemical reactions in organic materials, and examination of age-related effects in materials. These thrust areas are integrated with our continued mission of addressing directed nuclear weapons stockpile and external agency data needs.

Our measurements using embedded electromagnetic gauges to measure shock and reactive flow fields are unsurpassed and offer a unique, informative tool to apply to many scientific challenges. Our dynamic experiments are often performed in concert with ambient and high pressure sound velocity measurements (both ultrasound and Brillouin scattering), static high pressure spectroscopies and x-ray diffraction in diamond anvil cells, thermal analysis (differential scanning calorimetry and thermogravimetric analysis), optical and scanning electron microscopy, and dynamic spectroscopy and velocimetry techniques. Recent highlights include

• measurement of the first Hugoniot data for a number of relevant polymers and polymeric composites,
• completion of a large series of integrated experiments supporting the stockpile,
• observation of the first steady reactive wave in which the products are more dense than the reactants, and
• elucidation of the chemical sensitization of liquid explosives.

As a result of our combination of unique facilities and expertise, the group has been able to attract new funding and projects, including in the areas of threat reduction, work-for-others projects, and Department of Defense collaborations.