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

Abstract

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.

Crack resistance of fiber‐reinforced asphalt mixtures: Effect of test specimen and test condition

“…Based on the theoretical prediction of the generalized maximum tangential stress (GMTS) theory, the ratio of K IIc / K Ic was predicted equal to 1.31 for the ENDB specimen and 1.11 for the SCB specimen of this research by considering a typical value of critical distance ( r c = 0.6 mm) for the tested mixtures. This range was also used in previous works for concrete mixtures 6,10,78–80 . The consistency between the experimental fracture toughness ratios (given in Figure 6) and theoretical evaluations of the stress/strain‐based fracture models demonstrates that the mentioned criterion can provide good and acceptable predictions for the pure mode II fracture toughness of asphalt materials reinforced with fiber and tested with the SCB and ENDB specimens.…”

Effect of printing orientation on mechanical properties of SLA 3D‐printed photopolymer

“…Results indicated that the maximum relative error is 4.325% for a 2 mm wide prefabricated crack. 27 Therefore, the crack width is significantly smaller compared to the dimensions of the specimen in this study. The SIFs can be accurately obtained using Abaqus with an idealized crack model.…”

“…These were then laser‐cut into semi‐circular disks with matching orientations. An initial 8 mm crack was introduced into each disk using laser cutting, a technique chosen to minimize manufacturing errors, like inaccuracies in crack inclination angles 27,28 . Further refinement of the crack was achieved using a diamond wire saw, ensuring a precise crack length of 1 mm.…”

“…An initial 8 mm crack was introduced into each disk using laser cutting, a technique chosen to minimize manufacturing errors, like inaccuracies in crack inclination angles. 27,28 Further refinement of the crack was achieved using a diamond wire saw, ensuring a precise crack length of 1 mm. The effect of prefabricated crack width on stress intensity factors (SIFs) has been researched previously.…”

“…An average Young's modulus of E = 2.09 GPa and Poisson's ratio of v = 0.35 were employed. 27,32 The mesh pattern is shown in Figure 9, using singular CPS6 with quarterpoint positions middle nodes in the first ring around the crack tip, creating the necessary stress/strain field singularity near the crack tip. The FEM comprised primarily 8-node CPS8 elements, totaling 1,500 elements.…”