Numerical analysis of a new specimen for conducting fracture experiments under mixed mode I/III loading

Geometry of the specimen has been known to be one of the main challenges of determining the fracture strength of the materials. In this paper, a new specimen called "semi-disc bend specimen containing a 3D crack" has been proposed in order to study mixed mode I/III fracture behavior of the materials. This SCB specimen contains a tilted crack and is loaded by three-point bend fixture. Extensive three dimensional finite element analyses were carried out for different geometrical and loading parameters to obtain the stress intensity factors at the crack tip. The results showed that this specimen was capable of creating the mixed mode I/III loading such that the mode III component increases as the crack angle enhances. In the next step, in order to consider practicability of the proposed specimen, several specimens made of asphalt concrete were produced, and were then tested under different mixed mode I/III loading. The results showed that the suggested specimen can correctly simulate the mixed mode I/III loading. In addition, based on the experiments, fracture resistance of the asphalt concrete reduces as the mode III component increases. On the other hand, twisted fracture trajectory was observed from considering fracture surface of the specimens.