There have been a number of review papers on layered silicate and carbon nanotube reinforced polymer nanocomposites, in which the fillers have high aspect ratios. Particulate–polymer nanocomposites containing fillers with small aspect ratios are also an important class of polymer composites. However, they have been apparently overlooked. Thus, in this paper, detailed discussions on the effects of particle size, particle/matrix interface adhesion and particle loading on the stiffness, strength and toughness of such particulate–polymer composites are reviewed. To develop high performance particulate composites, it is necessary to have some basic understanding of the stiffening, strengthening and toughening mechanisms of these composites. A critical evaluation of published experimental results in comparison with theoretical models is given.

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Effects of particle size, particle/matrix interface adhesion and particle loading on mechanical properties of particulate–polymer composites

Crack deflection processes—I. Theory

On discute des mecanismes de renforcement des ceramiques par pontage des fissures a l'aide de trichites et d'autres types de renforcants discontinus. On montre que le renforcement par pontage des fissures peut etre combine avec d'autres mecaniques de renforcement (par exemple par transformation de phase) et que l'on peut obtenir des effets de synergie. La conception des materiaux renforces repose fortement sur le controle des proprietes des materiaux et des constituants microstructuraux

/pdf/microstructural-design-of-toughened-ceramics-1o4ydn67o9.pdf

Microstructural design of toughened ceramics

Toughening mechanisms of nanoparticle-modified epoxy polymers

Epoxy nanocomposites ¿ fracture and toughening mechanisms

Observations are presented showing that a crack front increases its length by changing its shape when it interacts with two or more inhomogeneities in a brittle material. These observations are presented for both cleavage and conchoidal types of fracture. Based on these observations and the concept that a crack front possesses a line energy, an expression for the fracture energy is obtained. This expression shows that the fracture energy should increase as the distance between the dispersed inhomogeneities is decreased. Using the Griffith fracture criterion, this result is discussed for the case of strengthening a brittle material.

The interaction of a crack front with a second-phase dispersion

Observations of the interaction of a crack front with cleavage steps on MgO fracture surfaces are presented and show that (a) steps exert a dragging force proportional to their height and (b) the crack front overlaps itself prior to the formation of the step. Based on these observations and on the hypothesis that a crack front possesses a line tension, a mechanism is proposed to explain the overlapping of one part of a crack front with the other, resulting in the formation of cleavage whiskers, steps undercut with cracks and foils of material that are associated with cleavage fracture. The energy absorbed during the parting of the steps is discussed.

F. F. Lange

Papers

The interaction of a crack front with a second-phase dispersion

Interaction between a crack front and cleavage steps