Mixed‐mode brittle fracture test of polymethylmethacrylate with a new specimen

A new test configuration called Holed-Cracked Square Plate (HCSP) is proposed to investigate I/II mixed-mode fracture of brittle and quasi-brittle materials. This specimen is a square plate containing a central hole with two radial cracks emanating from its circumference. The finite element method was used to calculate mode I and mode II stress intensity factors and T-stress solutions for various crack lengths and hole diameters. The numerical results show that a full range of fracture mode mixities can be realized by changing the orientation angle of two radial cracks, while maintaining a very simple specimen geometry and loading requirement. A series of fracture tests were conducted on Polymethylmethacrylate (PMMA) to study the practical capabilities of the HCSP specimen. These yielded fracture toughness values that are consistent with other experimental results. Other observed quantities including fracture initiation angles and fracture resistance also agree very well with mixed-mode fracture theories.