Predicting stiffness and strength of birch pulp : polylactic acid composites

This paper studies failure of birch pulp–polylactic acid composites. Stiffness and strength are calculated using the theory of short fibre composites and the results are compared to experimental data. The results differed from the experimental values by 0–6%. With less aligned fibres the short fibre theory is not feasible. The performance of the 40 wt% birch pulp – polylactic acid composite is predicted with X-ray microtomography based finite element modelling, and the results are compared with experiments. Stiffness results differed from experiments by 1–17% . By adding into the models a third material phase representing the interface between the fibres and the matrix, the stress–strain curve of the composite was obtained with good accuracy. The work presents finite element modelling methodology of wood plastic composites and the critical further steps needed in order to assess the stress–strain behaviour, strength and stiffness. Tools for comparing different wood plastic composite microstructures are also presented.