Figure 4. Description of biocomposite analogue, based on pine cone scale microstructure.

(a) Cross section SEM image of a pine cone scale highlighting a bilayer structure. (b) Flax fibres are strongly anisotropic and are used as a swelling agent in our analogue. A bilayer composite is manufactured with orientations of flax fibres (vf=60%) within each layer set at 0° and 90°, respectively mimicking the sclerenchyma fibres (passive layer with stiffness and low axial swelling) and sclerids (active layer with softness and high radial swelling) of a pine cone. Flax fibre content varies from 17, 40 to 60%.