The impact strength of the Mater-Bi and its biocomposites is
also enumerated in Table 3. The virgin Matrix did not break under
the previously specified test conditions. The Mater-Bi is ductile
and contains polar groups, which contribute to enhance the interaction
between the matrix and the Alfa fibers and therefore lead to
a relatively high value of impact strength even in the case of the
biocomposites. However, a drop of the impact strength in the biocomposites
was somehow expected because of the improved stiffness
and because of agglomerated fibers, which cause the crack
formation and propagation. The ductility of the biocomposites
slightly decreases with the increase in fiber loading from 15 to
25 wt% as reported in Fig. 7. In fact, at high fiber content, there is
no sufficient matrix-fiber contact, thus giving a low-energy path
for crack propagation. Consequently, in regions where fiber–fiber
contact dominates, the drop in the impact strength is a result of
the augmented fiber content [41]. Morreale et al. [25] suggested
similar results that wood flour reinforced Mater-Bi N matrix
showed a drop in impact strength and in elongation at break with
increasing the fibers content.