Explosives have been used for over a thousand years for various purposes. During most of that time, the emphasis has been on obtaining prompt initiation leading to detonation. This has been most often accomplished with a strong shock wave. In these situations, since the waves are all supersonic and at high pressure, confinement and material properties (e.g., strength, elastic behavior etc.) are unimportant or of secondary interest.
More recently, the emphasis has been on explosive behavior which is observed when weak shocks, or compressive waves, which are non-planar, interact with the reactive material. Now everything that was ignored previously, must be considered. This includes material properties, small amounts of chemical reaction, confinement, microstructure, etc. Modern explosives are composite materials having brittle and ductile phases, with behavior that is strongly nonlinear and temperature and pressure dependent. Treating these materials as continua is becoming less relevant.
This talk will describe explosives and their general behavior under various conditions. The approach will be from an experimentalist's perspective with an emphasis on diagnostic techniques used to probe the reaction progress, and recent results. Nonlinear optical probes, high speed visible and IR imaging, and other techniques will be discussed. The aim will be to provide an indication of the sort of basic questions that experimentalists address and explore, the extent of information modern diagnostic techniques can capture, and the behavior exhibited by real explosive materials.