Thermal and loading dynamics of energetic materials

Development of material models that can predict mechanical behavior, such as strength, damage and failure, are of great interest in polymer composites such as high explosives. Typically these materials have much higher solids loading (>90% by volume) than most structural engineering composites making property predictions difficult. The uniaxial mechanical properties of a high explosive (PBXN-9) and a mock explosive (900-21, a mock for PBX 9501) have been captured as a function of strain rate and temperature. The reason behind the characterization of the mock material is to find a non-hazardous material that has similar behavior and properties to the explosive. During the compressive characterization of the PBXN-9 HE it was found that there were significant differences between large and small sample sizes and this led to the size effect study described in this article. A split Hopkinson pressure bar (SHPB) was used to characterize the materials at high strain rates and a servo-hydraulic load frames were used for the characterization at strain rates from 100/s to 0.001/s as a function of temperature. Additionally, the deformation and fracture process of a semi-circular ring specimen made of the Mock HE was studied experimentally using the digital image correlation (DIC) technique. This new test geometry is complicated enough to challenge material models without being to complicated to develop a finite element mesh. This geometry of sample produces both tensile and shear failure modes which will be of great value, as the HE materials tend to go unstable in shear modes of failure.