Investigation of softwood fracture criteria at the mesoscopic scale

In order to improve the knowledge of softwood mechanical behaviour and particularly fracture mechanisms, investigation at small scales is needed. For that purpose, new numerical tools based on the real wood morphology in the transverse plane are specifically used. A mode I fracture criterion applicable to cracks oriented in the transverse plane in softwood is then studied at the mesoscopic scale, i.e. the annual ring scale. Numerical investigation combined with digital image correlation help to obtain wood fracture parameters in the annual ring. These parameters give additional knowledge and understanding of wood fracture according to local specificities such as crack tip position in an annual ring and notch orientation in relation to natural wood orientation and loading orientation. Mesoscopic fracture criteria can help our understanding of secondary crack appearance and crack arrest phenomena. Mixed mode study and coupling between mode I and mode II of fracture will be investigated further. Mixed mode fracture criteria can then help to better understand crack bifurcation phenomenon.