The objective of the research reported in this paper was to develop the grid method further for use in dynamic-stress studies. A rubber-thread grid network in a low-modulus model material (a urethane rubber known as Hysol 8705) was used in conjunction with a microflash light source to record grid distortions and photoelastic fringe patterns in a model subjected to dynamic-loading conditions. By considering a strut subjected to axial impact it was possible to establish that the static and dynamic values of Poisson’s ratio were identical, and the strain-fringe value of the material varied with strain rate. In addition, stresses in the axial and transverse directions were determined along the center line of the strut. Finally, the methods established were applied to the problem of a circular disk subjected to diametrical impact and both principal stresses were determined along a vertical diameter at one instant during impact.