This model is delineated by three regimes characterized by ductile deformation, where dispersion strengthening and stress concentration are the dominant factors; crazing, where debonding and cavitation occur; and brittle failure, where the fibrils in the ligaments fail.
These data show that neat RHDPE is the most ductile of the samples, which suggests dispersion strengthening by the fly ash particles .
Again, the standard deviations are such that the statistical significance of the published data are not conclusive but the present work and comparative studies I  and II  support the view that, at low fly ash addition levels, there is a modest increase in strength with fly ash additions, which is as expected owing to the likelihood of dispersion strengthening of this polymer .
This is attributed to the effect of dispersion strengthening moderated by stress concentration.
Because the data for tensile elastic modulus and tensile strength show maxima as a function of fly ash addition level, these data suggest that the increases resulted from dispersion strengthening. The decrease in tensile strength is attributed debonding and cavitation because it is clear that the decrease in the tensile elastic modulus was likely to have derived from the same phenomena and the SEM fracture surface images showed void formation, even though a silane coupling agent and compatibilizer were used to hinder this.
* Comparative study III : The intermediate particle size (<106 [micro]m) at low to medium volume fractions (~4.7-23 vol%) reveals the balanced opposition of dispersion strengthening and stress concentration.
These data are consistent with the gradual stiffening associated with dispersion strengthening.
* At low dispersant levels, the microstructures are dominated by dispersion strengthening, which is moderated by stress concentration.
The trend is a reflection of the dominant effects of dispersion strengthening at lower stress levels.
Traditional method of strength increase is dispersion strengthening by formation in the alloy structure of particles of high degree of dispersity (oxides, borides, nitrides).
One of possible methods of dispersion strengthening of titanium alloys is application of titanium intermetallics as refractory particles.