Study of the defect-crack offset distance on the impact fracture behavior of plexiglass

To study the interaction of moving cracks and pre-cracks of plexiglass (PMMA) under impact loading, a three-point bending experiment was carried out using dynamic caustics experimental system. Research showed that when the offset distance between the pre-crack and the defect is 9 mm, the failure mode of the crack is the most complicated. When the offset distance is 0 mm, the crack experiences the attraction force of the defect, the stress intensity factor and the crack growth speed increase gradually, and the peak value is reached when the defect and the crack intersect. When the offset distance is greater than 6 mm, the attraction effect of the defect on the crack is no longer significant, and the crack propagates toward the drop hammer location until it penetrates the specimen. As the crack propagates, the caustic speckle rotates counterclockwise and is subjected to compression and shear.