Evaluation of the Brazil Disk Testing Technique for the Rapid Determination of High Explosive Material Strength

Mechanical properties are a critical performance metric for many high explosive (HE) materials, and within the realm of mechanical properties, the tensile strength is particularly important.

Direct tensile measurements using dogbone shaped samples are the gold standard but they have the disadvantage that they are fairly large and require samples machined from larger

pressings. An investigation was undertaken to determine the feasibility of performing accurate tensile property measurements, particularly failure strength, using smaller and more easily

fabricated samples, such as Brazil disks. Brazil disks can be die-pressed and require smaller quantities of HE material. Summary highlights will be presented from a comprehensive critical

review examining literature results on using the Brazil disk technique to indirectly measure tensile properties in the fields of geology, pharmaceuticals, and high explosives. Despite the fact that the technique has existed since WWII there is currently no consensus on the accuracy of the Brazil disk technique or the preferred variant of the technique. Then experimental results

shall be presented from perhaps the most apples-to-apples comparison of the Brazil disk and tensile dogbone techniques performed to date. HE Brazil disk and dogbone samples were

extracted/machined from the same isostatically pressed billets to ensure material similarity, test temperatures were identical, and a digital image correlation technique was used to match

the tensile strain rate of the Brazil disk measurements to tensile dogone measurements (which rely on extensometers). We shall also compare the two leading Brazil disk variant techniques,

one using round Brazil disks with curved platens and one with flattened Brazil disks using flat platens, as well as compare isostatically pressed/machined samples with die-pressed samples.