ENF test set-up coupled with 3D DIC: (1) 300 kN load cell, (2) 5 kN load cell, (3) loading nose, (4) LVDT, (5) LVDT, (6) beech specimen, (7) speckle pattern, (8) supports, (9) DIC system equipment, (10) electro-mechanical testing machine frame
An experimental and numerical study on mode II fracture behaviour of European beech ( Fagus sylvatica L.) in the RL and TL crack propagation systems is performed. It is a hardwood species that has attracted increasing interest for structural use in Europe in recent years. Three-point end notched flexure tests are performed. The R -curves of both crack propagation systems are obtained, from which the critical strain energy release rate ( G IIc ) is derived by applying the compliance-based beam method. This data reduction scheme avoids crack length monitoring during its propagation, which is an advantage in wood. Using a direct method, the shear traction‐separation laws in mode II loading are determined. Full field displacements around the crack tip are monitored by 3D digital image correlation technique, and the crack tip shear displacements are analysed. The proposed method is numerically validated by finite element analysis. Cohesive zone models are developed implementing a shear traction–separation law with exponential damage evolution zone and the average value of the experimental elastic and fracture properties. The numerical results for the different properties including upper and lower limits represent well the experimental data.