Determination of interfacial parameters using micro-peel testing and cohesive zone modelling for wood fibre-polylactic acid composite

Precise engineering of biocomposites with micro-scale fibrous raw material is challenging due to the inherent heterogeneity, anisotropy, and variability of natural fibres. Micro-scale interface parameters are needed for multi-scale simulations, e.g., representative volume elements (RVEs). This study develops a procedure to test and numerically evaluate the interface between very short pulp fibres and polylactic acid (PLA). The work begins with mechanical and geometrical characterization of single fibres and PLA. After micro-peel testing, post-test characterization includes scanning electron microscopy, optical projection tomography, X-ray computed micro-tomography, and 3D profilometry to determine fibre geometry and fracture surface details. Finite element (FE) models with cohesive zone model (CZM) interfaces are used for micro-peel evaluation. The results reveal how the fibre geometry and material modelling influence the response of the micro-peel test. The fracture surface modelling is found to be crucial in fitting the fracture energy (ERRcc) and critical tractions (Tcc) of the CZM interface. Values of 50 J/µ m² (ERRcc) and 138 N/µ m² (Tcc) are determined when linear-elastic modelling is used, respectively. An isotropic linear-elastic fibre with plasticity modelled for PLA results in fitted ERRcc and Tcc values of 50 J/µ m² and 70 N/µ m², respectively. When transversely isotropic pulp fibre and plasticity for PLA are modelled, ERRcc and Tcc values of 55 J/µ m² and 74 N/µ m² are best fitted, respectively.