Toughening mechanisms microcracking

Other toughening mechanisms microcracking, inclusion debonding and pull-out... 

It is important to note that in contrast to ZTA toughened by microcracking, transformation toughening can lead to an improvement in both toughness and strength and, consequently, is the preferred toughening mechanism. 

Figure 10. Schematic presentation of toughening mechanisms. Frontal-wake mechanisms (a) dislocation glide, (b) microcracking, (c) phase transformation, (d) ductile second phase. Bridging mechanisms (e) grains, (f) fibers, (g) whiskers, (h) ductile second phase. Reproduced with permission of.(9).

Fabrication of SiC composites by second-phase dispersion is widely applied to improve material toughness. The various toughening mechanisms [93] that have high potential to reduce crack extension in SiC- composite materials are crack deflection, microcrack formation, crack bridging by reinforcement with metallic ligaments (e.g. TiC, TiB2), and crack bridging and pull out by platelet- or fiber-reinforcement. 

Figure 14. Potential toughening mechanisms for SiC based ceramics 1 crack deflection, 2 microcrack formation, 3 crack bridging with metallic ligaments, e.g. TiB2, 4 crack bridging and pullout by platelet or fiber - reinforcement.

How would you propose to quantity the relative values of crack pinning, microcracking, and crack path deflection toughening mechanisms in a mica-reinforced epoxy resin Draw pictures of possible morphological changes. [Hint Mica forms thin platelets under these conditions.]... 

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