Fracture toughness bridging

Figure 48. Fracture toughness (Bridge method) vs. mean grain size and free carbon content (after [210]).

The important case of specimens with a fixed total thickness was considered in Ref. [40]. There are certain features of crack bifurcation under these conditions, such as that if the sample with a fixed total thickness has too large a number of layers there will be no bifurcation. Layer thickness and composition are important and efficient parameters to control the bifurcation in laminates. The effect is comparable with a crack bridging phenomenon [21], The bifurcation mechanism increases the laminate fracture toughness by approximately 1.5-2 times. 

The dispersion of SiC-coated MWCNTs increases the microhardness and fracture toughness of SiC. The SiC coating on MWCNTs at 1150°C is effective in improving the weak adhesion between MWCNTs and the SiC matrix. SiC-coated MWCNT/SiC composites show elastic behavior due to the crack-bridging effect of MWCNTs. 

Kb accordingly represents the toughening provided by the bridging zone. If failure of the composite occurs at Keff = Kc (the fracture toughness), then the fracture resistance, KR is given by... 

In order to apply the characterization and structural design of the concrete bridge structures retrofitted with tensioned carbon fiber sheets, the mixed mode disk specimen was proposed and applied to the mixed mode fracture toughness tests. The following conclusions were derived from the results and discussions ... 

Fracture toughness, delamination, 3D composite, bridging law, crack opening displacement. 

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