Mode-II Fracture Response of PMMA Under Dynamic Loading Conditions

The mode-II dynamic fracture behavior of poly(methyl methacrylate) (PMMA) was experimentally and numerically studied using ultra high-speed photography combined with digital image correlation and meshfree numerical simulations. Experiments were performed by launching a projectile from a gas gun onto pre-notched rectangular PMMA specimens. Two sample geometries were used, double edge notch specimens and single edge notch specimens. Additionally, two variations of the single edge notch specimen experiments were performed, in the first experiment the projectile directly hit the sample and in the second one a buffer was placed between the sample and projectile to ensure uniform loading. Finally, the effect of the notch sharpness was explored. The impact location was below the notch to ensure mode-II loading, which would then transition into mode-I loading once the crack starts to grow. Mode-II critical stress intensity factors were extracted and it was found that notch sharpness and loading conditions can have an effect on the path the crack follows upon fracture. All of these results were compared to numerical simulations of the crack propagation processes using a meshfree method. The numerical model successfully predicted the fracture toughness and the crack-path angle within 4% and 7% of experimental values, respectively. In addition, crack-tip speeds greater than 300 m/s were observed experimentally and numerically.