One of the main factors contributing to the failure of composites is the failure initiated at the interfaces. Examples include interface failure at interfaces such as those between HTPB-Ammonium Perchlorate (AP) in an example energetic material. One important characteristic that could be used to develop failure theories under dynamic loading in materials with an account of interface properties is constitutive properties of interfaces under dynamic loading. In this work, interface mechanical strength of a set of HTPB-AP interfaces is characterized using dynamic indentation experiments at strain rates up to 100 s-1. Stress maps were measured in the interface areas using Nano Mechanical Raman Spectroscopy (NRS) to analyze the changes in the stress distribution around interfaces. Measurements of dynamic hardness, strain rates, and plasticresidual depths were correlated to show the relation of interface mechanical strength with the bulk phase mechanical strength. A power law viscoplastic constitutive model was fitted to experimental stress-strain-strain rate data in order to obtain constitutive behavior of interfaces, particle, and matrix. Results show that interfacial properties are affected by the rate of loading and are largely dependent upon the interface structural inhomogeneity. Stress maps are obtained near the interface using In-situ Mechanical Raman Spectroscopy to analyze the changes in the stress distribution around interfaces for different loads. A bilinear cohesive zone model parameters were obtained from the consideration of local stress and the cohesive energy required for delamination. © The Society for Experimental Mechanics, Inc. 2017.