Relationship of fragment size to normalized spall strength for materials

A systematic study is described which addresses the technical issues associated with launching plates to hypervelocities using compressed helium gas as the driving medium. Similar acceleration rates are used to drive constant-mass flier plates, while the material properties such as the shock impedance, yield strength, and spall strength are varied. Results of these experiments indicate that, due to the severity of loading, the flier plates have a tendency to fragment following peak acceleration. Each material has its own unique fragment distribution. More significantly, these experiments suggest a direct dependence of the mean fragment size to its normalized spall strength, i.e., the spall strength divided by its density. A method is also proposed for successfully launching intact plates to hypervelocities.