Silicon strength distribution

Another feature of this material is its narrow distribution of the fracture strength. When the strength distribution was expressed in Weibull statistics, the Weibull modulus was 46 - substantially higher than the value of 26 obtained for a conventional, self-reinforced silicon nitride. Thus, the seeded and tape-cast silicon nitride showed a synergistic improvement in all of the important fracture attributes, such as fracture strength, fracture toughness, and strength stability (Weibull modulus). 

Figure 12.11 Strength distribution of a silicon nitride ceramic (same data as in Figure 12.8). A Weibull distribution function (solid curve) and a Gaussian distribution function (dashed curve) are fitted to the data. The data are plotted (a) in...

K. Goda and H. Fukunaga, The evaluation of the strength distribution of silicon carbide and alumina fibres by a muti-modal Weibull distribution, J. Mater. Sci., 21,4475-80 (1986). 

Molecular mechanisms for stress-softening are also discussed. It is shown that this phenomenon is not related to the chain slippage or to a conversion of a "hard" adsorbed phase to a soft one. The obtained results assume that the stress-softening in silicon rubbers is caused by two possible reasons changes in the positions of filler particles relative to the direction of stretching at the first deformation and by a re-distribution of the topological hindrances. It is shown that the tensile strength at break as a fiinction of temperature is closely related to the chain dynamics at the elastomer-filler interface. 

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