Research on crack expansion characteristics of semi-disc polymethyl methacrylate specimen with weak prefabricated double-layer surfaces under dynamic load

In this study, based on an experimental digital laser dynamic caustic system, a dynamic fracture experiment on a polymethyl methacrylate (PMMA) semi-disc specimen with a weak precast double-layer surface under an impact load was carried out, the cracking, expansion, and wearing patterns of the cracks under different tilt angles (60°, 45°, and 30°) were studied, and the changing characteristics of the trajectory, velocity, and dynamic stress intensity factors of a crack expansion were compared. In addition, a newly developed discrete lattice spring method was adopted to simulate the expansion of dynamic cracks in a PMMA specimen with weak double-layer surfaces, and it was found that this numerical model can reproduce experimental phenomena for analyzing the effects of a weak surface spacing on the crack expansion. Combined with the test and numerical analysis results, it can be concluded that the tilt angle and spacing of a weak double-layer surface will have a significant influence on the crack expansion characteristics.