Toughness Characterization

Some investigations [105-107] on micron-.size particle-filled composites demonstrated that fracture toughness is dramatically influenced by the particle shape, size, volimie fraction, and particle/matrix interfacial strength. Brunner et al. [108] reviewed the development of fracture mechanics test methods in determination of fracture toughness and delamination resistance of fiber-reinforced polymer composites. 

Although the expressions for and its relation to are originally derived for homogeneous, isotropic materials, it has been successfully utilized for particle-filled composites as follows  

However, the toughness characterization of the more ductile polymer composites is more challenging. Traditionally, toughness of these composites has been characterized 

Hristov [123] studied the impact fracture behavior of WPG modified by MAPP as compatibilizer and poly (butadiene styrene) rubber as impact modifier using Gharpy impact testing. They demonstrated that the crack propagation energy compared to the crack initiation energy is much more influenced by the morphology. 

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McCaffrey. T.J. Combined Strength and Toughness Characterize New Aircraft Alloy/ Materials Processes. 47 (September. 1992),... 

Many variables used and phenomena described by fracture mechanics concepts depend on the history of loading (its rate, form and/or duration) and on the (physical and chemical) environment. Especially time-sensitive are the level of stored and dissipated energy, also in the region away from the crack tip (far held), the stress distribution in a cracked visco-elastic body, the development of a sub-critical defect into a stress-concentrating crack and the assessment of the effective size of it, especially in the presence of microyield. The role of time in the execution and analysis of impact and fatigue experiments as well as in dynamic fracture is rather evident. To take care of the specihcities of time-dependent, non-linearly deforming materials and of the evident effects of sample plasticity different criteria for crack instability and/or toughness characterization have been developed and appropriate corrections introduced into Eq. 3, which will be discussed in most contributions of this special Double Volume (Vol. 187 and 188). 

Sokolov M A, Nanstad R K and Miller M K (2004), Fracture toughness characterization of a highly embrittled RPV weld, pp. 123-137 in Effects of Radiation on Materials, AS>Tyi STP1447, M L Grossbeck, ed., ASTM International, West Conshohocken, PA. 

Fracture toughness characterization has been discussed throughout this article from different view points. It requires well-defined specimens and procedures, which have already been indicated. For convenience this information is here summarized again. 

New ceramic material specifications may incorporate fracture toughness characterization. One example is the new ASTM Standard F 2094 -01 for silicon nitride ball bearings. Three grades of bearing balls are specified in this standard and fracture... 

Lu ML, Chiou KC, Chang FC. Fracture toughness characterization of a PC/ABS blend under different strain rates by various J-integral methods. Polym Eng Sci 1996 September 36(18) 2289-95. 

N. Banthia and J.F. Trottier, Concrete reinforced with deformed steel fibers. Part II toughness characterization , ACi Mater. J. 92,1995,146-154. 

N. Banthia and S. Mindess, Toughness characterization of fiber-reinforced concrete Which standard to use , J. Test Evai. 32, 2004,138 142. 

G. Campione and S. Mindess, Compressive toughness characterization of normal and high-strength fiber concrete reinforced with steel spirals , in N. Banthia, C. MacDonald and P. Tatnall (eds) Structural Applications of Fiber Reinforced Concrete, SP-182, American Concrete Institute, Farmington Hills, Ml, 1999, pp. 141-161. 

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