Low velocity surface fracture patterns and energies in poly(methyl methacrylate)

Steady-state fracture techniques were used to investigate the surface fracture patterns and surface fracture energies of poly(methyl methacrylate) at low velocities (10 cm/sec to 10^?5 cm/sec). Several anomalies were discovered: (1) Small surface cracks, running parallel to the crack front, which were initiated by imperfections; (2) a “zero velocity” transition from the normal surface fracture patterns to a “laminar” pattern; and (3) a subsequent transition from the laminar pattern to a “turbulent” pattern. The velocities at which these anomalous fracture patterns occurred were of the order of 10^?4 to 10^?6 cm/sec. The corresponding surface fracture energies were as low as 10⁵ erg/cm².