Fracture toughness particle

The other alternative is to attempt to increase K -. Pure ceramics have a fracture toughness between 0.2 and 2 MPa m. A dispersion of particles of a second phase can increase this a little the advancing crack is pinned by the particles and bows between them, much as a dislocation is pinned by strong second phase particles (Chapter 10). 

Composite Particles, Inc. reported the use of surface-modified rubber particles in formulations of thermoset systems, such as polyurethanes, polysulfides, and epoxies [95], The surface of the mbber was oxidized by a proprietary gas atmosphere, which leads to the formation of polar functional groups like —COOH and —OH, which in turn enhanced the dispersibility and bonding characteristics of mbber particles to other polar polymers. A composite containing 15% treated mbber particles per 85% polyurethane has physical properties similar to those of the pure polyurethane. Inclusion of surface-modified waste mbber in polyurethane matrix increases the coefficient of friction. This finds application in polyurethane tires and shoe soles. The treated mbber particles enhance the flexibility and impact resistance of polyester-based constmction materials [95]. Inclusion of treated waste mbber along with carboxyl terminated nitrile mbber (CTBN) in epoxy formulations increases the fracture toughness of the epoxy resins [96]. 

Increase fracture toughness or strain energy release rate Strongly influenced by formulation and compatibility of binder with primary particles... 

Hing P. and Groves G.W. (1972). The strength and fracture toughness of poly-crystalline magnesium oxide containing metallic particles and fibers. J. Mater. Sci. 7, 427-434. 

Hydroxyapatite (HAP), with basically the same crystal structure as Ca-deficient, carbonate-containing hydroxyapatite, is compatible with and reactive in a live human body. However, sintered HAP prepared by treating fine HAP particles under elevated temperature and pressure has insufficient mechanical properties, in particular fracture toughness, which greatly limits its commercial applicability. It is rarely implanted alone. On the other hand, zirconia, particularly partially stabilized zirconia (PSZ),... 

Table 10.4 Comparison of Vickers hardness and fracture toughness for cemented carbide sintered with and without SiC-coated diamond particles...

Dense composites of cemented carbide containing SiC-coated diamond particles can be fabricated without conversion of diamond to graphite. The fracture toughness of the composite is double that of cemented carbide due to the deflection and blocking effects against crack propagation by the dispersed diamond particles. 

Although fracture toughness can be increased, particle- or whisker-reinforced sialon composites generally show brittle behaviour and low damage tolerance this is in contrast to fibre-reinforced sialons which exhibit non-catastrophic failure. 

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