Mixed-mode cohesive zone modeling and damage prediction of irregular-shaped interfaces in wood-plastic composites

Debonding is the dominant fracture mechanism in wood-plastic composites, and the direction of wood fibrils significantly affects the normal and tangential wood-plastic interfacial properties. This study was aimed at simulation of the mixed-mode damage initiation and growth in wood-plastic interfaces using the cohesive zone model. The wood-plastic interfacial properties in longitudinal and transverse directions were determined. The opening and sliding displacements across the wood-plastic interfaces were measured by means of digital image correlation techniques, and the force-displacement diagrams were obtained from the experimental data. The Nelder-Mead algorithm was employed to identify the wood-plastic cohesive parameters through optimization of the force-displacement results of the numerical simulation and experimental data. Accordingly, the obtained cohesive parameters were implemented in the finite element (FE) models for damage prediction of the irregular-shaped particles in wood-plastic specimens. Very good agreements were found between the FE simulations and the observed fracture patterns .