This
phenomenon can be clearly explained by SEM micrographs,
as shown in Fig. 2. Fig. 2a–2d show the grooved
surface of the rice hull particle and the interfacial cavities
generated due to the poor interfacial adhesion. For
the finer milled rice hull particles, there was greater
surface area for more cavities to be created and acted as
internal defects reducing the efficiency of the energy
transferred within the composites upon impact.