After the Izod impact test, SEM micrographs (Figs. 12 and 13)
of fractured surfaces revealed similarities but also important differences
among the composites. In fact, SEM images indicated that
the phenomenon of “pull-out” and the related formation of voids
occur at different extents for all the specimens. In Fig. 12 the good
interaction at the interface between the matrix and the fibers can
be observed. For curaua and sisal fibers, the adhesion was probably
enhanced by the surface roughness which promotes the formation
of mechanical bonding between the matrix and the reinforcement.
It is interesting to note that crack propagation was hindered by a
sisal fiber (Fig. 12d). Bagasse and coconut fibers, despite their strong
aromatic character, showed good adhesion at interface. SEM images
of fibers tips (Fig. 13) show a poor filling by the polymer of the internal
hollow structure of sugarcane bagasse and coconut and a good
– although not complete – filling in the case of curaua and sisal
fibers.