The latest results from a study of the dynamic behavior of rain erosion-resistant coating and substrate materials are described. The correlations between rocket sled erosion data and fracture stresses determined from single-impact tests with a split Hopkinson pressure bar facility have been extended to include polyurethane. The results of tests within a small-scale erosion facility, and analyses of large whirling-arm studies, have shown that a fatigue type of behavior, already found to be applicable for an acrylic plastic, may also be used to describe the rain erosion resistance of elastomeric coatings such as polyurethane, and the glass fiber-reinforced epoxy composite substrates which are frequently utilized for radome construction. The importance of the “dynamic recovery rate” or relaxation time, and stress wave interactions, in understanding the rain erosion phenomenon is described in this paper. The applicability of the elastic-plastic, uniaxial stress wave theory for making rain erosion predictions is also discussed.