From the results shown in Table 3, both physical and practical adhesion of flax/polypropylene system are substantially lower than those of flax/epoxy, which indicates poor fibre-matrix adhesion between flax and polypropylene. Therefore, both CP and UD flax/propylene composites experiences delamination when subjected to shock impact as seen in Fig. 6b and c. On the contrary, the high interfacial adhesion of flax/epoxy could be from the contribution of chemical bond between the flax fibre and the reactive epoxy. Fig. 6a shows a piece of the broken test sample UD1_FF_EP with its side showing clear sign of clean and sharp break off from the main piece due to brittle epoxy matrix and the strong interfacial adhesion.