Soft matrix fracture

Lednicky, E and Michler, G.H. (1990) Soft matrix fracture surface as a means to reveal the morphology of multi-phase polymer systems, /. Mat. Sci., 25, 4549-4554. 

In early nanocomposites, hard and strong dispersoids, such as SiC, Si3N4, TiC, etc., were mainly incorporated into the matrix to improve the mechanical properties. But in later years, enhancement of fracture strength was also achieved by addition of even soft and weak dispersoids like metals, graphite and h-BN [3-5], The density, microstructure and mechanical properties of nano-sized particulate dispersion nanocomposites were strongly dependent on the volume fraction of particulate dispersion and sintering conditions. 

The interphase provided by the adhesion promoter may be hard or soft and could affect the mechanical properties. A soft interphase, for example, can significantly improve fatigue and other properties. A soft interphase will reduce stress concentrations. A rigid interphase improves stress transfer of resin to the filler or adherend and improves interfacial shear strength. Adhesion promoters generally increase adhesion between the resin matrix and substrate, thus raising the fracture energy required to initiate a crack. 

Unlike fracturing, this approach should cause only moderate disruption of the coal matrix and might not lead to complete comminution, but this method could be envisioned as a prelude to coal grinding. Removal of material from structural boundaries would yield a more friable, "soft" coal structure. The leaching of fine mineral particles from the coal matrix results in a more porous structure and should also improve the coal s grindability. The prior removal of some mineral matter would also reduce the coal s abrasiveness. 

If the matrix material is brittle, large deformation will lead to fracture, but then we are outside the realm of soft solids. 

Figure 7.18 shows schematic crack paths through (a) water ice and (b) ice cream. The weakest part of the water ice microstructure is the ice-matrix interface, so the crack follows a path along the edges of the ice crystals as far as possible. In the ice cream, the air bubbles are the weakest links so the crack passes through them. The ice crystals are the most fracture-resistant components so in both cases the crack passes around them. Ice cream is effectively a particulate-reinforced composite material, i. e. a material in which tough particles are embedded in a relatively soft continuous phase in order to increase the overall fracture resistance. Since the microstructure is heterogeneous, it is not possible to predict exactly where the crack will form or precisely what path it... 

It has been mentioned previously that cohesive fracture occurred when a soft resin was used as the matrix of such dismantlable adhesives [5]. However, with... 

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