Measurement of three-dimensional deformation of an interfacial crack in a bimaterial

An interfacially cracked bimaterial beam made of two different types of polyester resins was studied under loading of four-point bending. Three layers of random speckle patterns were seeded in the specimen. The white light speckle method was used to obtain the surface displacements and the interior displacements along the crack faces. The results revealed that there existed a mixed-mode field near the crack-tip but it was dominated by an opening-mode, and the opening displacement of the crack measured in the free surface was approximately twice as large as that in the interior. The experimental results imply that the effect of the free surface is more significant than that in a homogeneous material.