Modeling the fiber bridging effect in cracked wood and paperboard using a cohesive zone model

Wood and paperboard are two of the most widely used structural and packaging materials. Their fracture mechanical properties play a critical role in their performance for the practical applications. Cracks may lead to the creation of bridging fibers across the crack surfaces in both materials, which complicates fracture measurements and modeling. The aim of this study is to predict the fracture behavior including the fiber bridging contribution by using a potential based cohesive law in a phenomenological way. The cohesive energy potential was constructed using an exponential function, and the cohesive traction-separation relationships were obtained from the gradient of the potential. The model was applicable to various traction increasing responses, i.e. convex and concave. The proposed model was evaluated by simulating the double cantilever beam (DCB), end-notched flexure (ENF), and mixed mode tests. The results agree well with experimental data.