Volume 22, Issue 4 (July 1994)
A Suggested Test Procedure to Measure Mixed Mode I–III Fracture Toughness of Brittle Materials
This article describes a test procedure to measure mixed mode I–III fracture toughness. The traditional compact tension specimen geometry is modified to include an angled crack slot. This angle is varied to produce various mode I/mode III ratios. A further modification to the specimen design involving two crack fronts in a triple “pantleg” configuration that can produce near-mode III loading at the crack tip is also described. Together, these two specimens can be used to test the entire spectrum of combined mode I–III. Results of mixed mode fracture tests on 2034 aluminum alloys using these specimens are presented. A three-dimensional (3-D) finite element model of the modified compact specimen to validate the analytical procedure is also described. Angular correction factors for the mixed mode case are also presented. The results indicate the feasibility of developing a new standard test method to measure mixed mode fracture toughness in macroscopically brittle metallic materials.