An innovative DIC-assisted configuration for testing high-speed dynamic crack propagation in brittle materials

High-speed crack propagation is widely recognized as a governing factor in the strength, energy-absorption capacity and catastrophic failure modes of brittle materials. In this work, a wedge-notch circular-end (WNCE) specimen was developed and employed in a split Hopkinson pressure-bar system to interrogate dynamic fracture in Polymethyl methacrylate (PMMA) material. A 75 mm unobstructed, mode-I ligament was provided, while a semi-circular tail was designed to decouple the specimen passively from the bars after the first stress pulse. Ultra-high-speed digital image correlation (350 kfps) was applied, permitting full-field displacement and principal-strain mapping at micro-second resolution. Stress-rate ramps of 255–790 GPa/s were imposed; force-equilibrium conditions were achieved for all tests. Crack velocities were observed to rise monotonically from 624.78 m/s to 1211.99 m/s, thereby demonstrating stable, single-front acceleration into the near-Rayleigh regime. Self-similar process-zone shapes were documented throughout propagation. The WNCE geometry enables quantitative measurement of the complete high-speed fracture process in brittle solids.