Particle diameter stress-concentration zone

Particle Diameter. The increased stress around the equator of particles is larger than the outer stress, aQ, in a zone within an angle range of 35° (12). So the size, Dz, of this stress-concentration zone has the same magnitude as the particle radius, D/2 ... 

Particles whose diameters are significantly greater than Dopt are less effective for craze initiation. The stress-concentration zone is much broader than the optimum thickness of crazes. Therefore, several thinner crazes having a total volume smaller than the volume of a craze with a thickness equal to Dz are initiated (3,19). 

The experimental results clearly reveal that the size of the stress-concentration zone, that is, the diameter of the rubber particles, is the primary factor for the initiation of crazes. Therefore, the effectiveness of the different-sized rubber particles can be shown in an effectiveness curve, which gives the probability of the particles to initiate craze (19, 22). Starting from Dmin for craze initiation, the effectiveness of particles of different sizes increases up to a maximum and then drops at larger diameters. 

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