The dark regions in the paper layer observed in Fig. 12 correspond to defects or porosities that reduce the strength of paper/PLA layer, thus resulting in delamination zones on the fracture surface of PLA/Flax-paper composite as shown in Fig. 7. Works are underway to increase the permeability of paper layer to reduce the porosity in the molded composites and maximise the mechanical properties obtained with these reinforcements [30,41,42].