Mechanical performance of wood subjected to the interaction of transversal tension/compression and longitudinal shear stresses

The interaction of transversal tension/compression stress with longitudinal shear stress extensively exists in practical timber components. Thus, the investigation of the mechanical properties of wood subjected to such loads is of particular significance. In this paper, forty-eight larch wood specimens were prepared, the configuration of which resulted from a modification of the most sophisticated V-notched shear specimen to consider the normal loading requirement. Experiments were carried out on an MTS uniaxial testing machine responsible for the shear loading. An auxiliary device was designed and equipped to the testing machine to produce constant normal load. Digital Image Correlation (DIC) technique was used to record the full field deformation and the whole failure process. Failure modes, and shear stress-strain curves under different normal stresses were obtained. The applicability of several commonly used orthotropic strength criteria including Hill, Tsai-Hill, TsaiWu, Hoffman, van der Put, Norris, and SIA 265 criteria, et al. to predict the combined transversal tension/ compression and longitudinal shear failure were systematically assessed according to test data from the experiment as well as existing literature. Results indicated that transversal tension stress promotes shear failure, while compression stress has a suppressive effect on shear failure. The longitudinal shear strengths can be evidently raised by increasing transversal compressive stresses, while tensile stress reduces the longitudinal shear strength. Van der Put and SIA 265 criteria are most suitable to predict the longitudinal shear failure of wood under different normal stresses, and the former produces the least error. In addition, the best applicable normal stress ranges of the examined failure criteria were confirmed.