Stiff macroscopic defect

The results of comparison for HDPE samples with sharp notch and without it show, that notch (stiff macroscopic defect) introduction results to V reduction, that is, local order level enhancement, which is expressed in mechanical vitrification of devitrificated amorphous phase part [59]. This effect defines molecular mobility considerable reduction, expressed by decrease, and reduction. The last factor results to d decrease up to the values typical for quasibrittle fracture, that is, d < 2.5 [6]. 

Hardness is a measure of a material s ability to resist elastic and plastic deformation. The hardness of non-ideal material is determined by the intrinsic stiffness of the material, as well as by the nature of its defects, be they point defects, dislocations, or macroscopic defects such as microcracks etc. For ideal systems, the hardness of a material will scale with its bulk modulus. 

In recent years, the limits of optimizing composite properties of traditional micrometer-scale composite fillers have been reached due to the compromises of the obtained properties. Stiffness is traded for toughness, or toughness is obtained at the cost of optical clarity. In addition, regions of high or low volume fraction of filler often results in macroscopic defects which lead to breakdown or failure of the material. Recently, a new research area has provided the opportimity to overcome the limitations of traditional micrometer-scale polymer composites. This new investigation area is the nanoscale filled pwlymer composites where the filler is <100 nm in at least one dimension. 

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