In this study, crack resistance is evaluated by the crack tip opening angle (CTOA) using a wedge splitting test (WST)on a viscoelastic particulate reinforced composite based on an HTPB binder. Generally, CTOA, as a function of crack extension, is used in order to determinate fracture resistance and has a steady state relative angle. Digital image correlation (DIC) is used to measure the crack tip opening displacement (CTOD) and crack extension for the critical crack tip opening angle (CTOAc). In these results, the CTOAc value of a particulate reinforced composite tends to approach a constant angle after a small amount of crack extension. The CTOAc value increases with decreasing temperature, from 50 degrees C to -40 degrees C. These CTOAc values may be used to measure fracture mechanics parameters for particulate reinforced composite.