The notched and unnotched Izod impact strengths of the composites at different filler contents are shown in appeared at the filler-matrix interfacial area in the filler
contained unnotched sample.
As can be seen in Fig. 6, unnotched Izod impact
energies were considerably larger than notched Izod
impact energies. This is due to the different fracture
process for notched and unnotched samples. The unnotched
impact behavior is controlled to a considerable
extent by fracture initiation processes that, in turn, are
controlled by stress concentrations at defects in the
system. Notched impact behavior, meanwhile, is controlled
to a greater extent by factors affecting the
propagation of fracture initiated at the predominating
stress concentration at the notched tip. In other words,
unnotched Izod impact energies are not only a measure
of crack propagation but also of crack initiation [3,11].