Analysis of In-plane Shear Behavior of Wood Based Panels by Digital Image Correlation
Michiharu IKEDA, Minoru MASUDA, Koji MURATA and Seiichiro UKYO
Abstract:Failure of various types of wood-based panels was observed under in-plane shear. The notched specimens were loaded for a shear test in a manner similar to that for a two-rail shear test. The shear behavior was recorded using a digital camera and analyzed by digital image correlation. During the shear test, initial cracks were formed on the notch in almost all of the specimens. As the load increased, the cracks propagated in an inclined direction. The propagation appears to be due to tension fracture under principal stress. Only in conifer plywood, the initial crack resulted from a split of the surface veneer, and the fibers therein peeled with an increase in the load. Since various fracture shapes were observed in the different types of wood-based panels, the formation process of the final fracture would depend on the mechanical properties of the constituting element (fiber, strand, or veneer). Strain distribution between the notches was measured by digital image correlation, and the "true curve of stress-strain" under in-plane shear was derived. Even if the specimen exhibited a stress concentration area, its shear modulus could be calculated from the curve. Moreover, it was observed that stress decreased with an increase in the shear strain in nonlinear region of the true curve of stress-strain. The initial fracture could not develop immediately into the final fracture, and it probably remained in the form of a small crack. Key Words:Shear modulus, Wood based panel, Digital image correlation, Strain analysis, Notched specimen