THE FIRST SHOCK COMPRESSION EXPERIMENTS ON SEPIOLITE: IMPLICATIONS OF GEOTECHNICAL MATERIALS FOR BLAST MITIGATION

Blast mitigation is an important geotechnical engineering endeavor driven by warfare, infrastructure stability, and crisis management. Identifying low-cost materials that can absorb shock is critical to technology development within the context of infrastructure shielding. This investigation reports the initial evaluation of sepiolite as a material to be used for blast mitigation. Sepiolite is abundant in certain regions of the world and could potentially be supplied globally for applications in geotechnical engineering. Shock compression experiments were conducted at University of Illinois at Urbana Champaign (UIUC) in an inverted shock microscope where laser driven flyers (0.5 mm diameter discs of thin metal foil) are used to apply high-pressure to the target mineral. The shock compression apparatus uses a high-energy laser to launch flyers, which then travel at high velocities before impacting a sample, thereby compressing it. Because of the hypervelocity impact, the flyer sends a shock wave into the sample. The pressure applied to the sample is directly proportional to the shock amplitude, controlled by the impact velocity of the flyer. The experiments reported here on sepiolite were performed using 25 µm Al flyers with 3.5 km/s impact velocities to produce planar shock waves of 5 ns duration in the sample. Transmission electron microscopy of pre- and post-shocked sepiolite particles indicates that the minerals’ crystal structure experienced moderate to severe damage. Overall particle size and shape appear to be retained. The proposed mechanism of “shock survival” is thixotropic in nature but also likely relies on collapse and deformation of the zeolite-like tunnels in the crystal structure. Further experiments include investigation of modified sepiolite to gain insight into the mechanisms of “shock survival”.