On the Development of High Strain Rate Experiments for the Characterization of Engineering Materials

In order to predict the damage accumulation and failure processes associated with highly dynamic events such as blast loading, shock wave loading, and ballistic impact loading, a commensurate understanding of the fundamental constitutive and fracture behavior of materials subjected to such high rate loading conditions is necessary. In this effort, high strain rate experimental facilities consisting of a shock tube apparatus and a torsional split Hopkinson bar apparatus have been designed, constructed, and subsequently used to investigate the mechanical properties of an array of engineering materials subjected to a variety of dynamic loading conditions. Designs for the experimental equipment utilized are based mostly on modified versions of established equipment already in use elsewhere; however improvements have been implemented wherever possible with an emphasis on reliability, robust design, and versatility. Fabrication of all equipment was performed by the author. Three experimental works conducted using these experimental apparatuses are presented, each considering a unique engineering material and dynamic stress state. 1) Pre-stressed orthogonally woven composites were subjected to shock loading, and the effect of loading rate and fiber orientation on both fracture toughness and crack growth direction is presented. 2) Rigid closed cell foams were subjected to compressive shock loading and the effect of foam density and strain rate on the compressive properties of the foam is presented. 3) Finally, a high strength aluminum alloy is subjected to high strain rate torsional loading, in as-received and friction stir welded states, and the effects of microstructure and strain rate on the shear properties of the alloy are presented. The wide variety of materials tested and the diverse array of dynamic stress states achieved serve to illustrate the versatility and effectiveness of the experimental equipment constructed and utilized in this work