Craze Breakdown Statistics

The statistics of craze fibril breakdown have been found experimentally to follow a Weibull distribution with respect to the plastic strain e = e — e, i.e. 

Physically the Weibull parameters and are constants, unlike the median strain for fibril breakdown which depends on the size of the sample tested. The size effect 

The size effect can be demonstrated nicely using different size film squares As shown in Fig. 33 a, the breakdown probability for the crazes in a small grid square that is 9 times smaller in area than a larger grid square is much lower at a given 

Breakdown probability pi, versus s for large and small grid squares in a 1,800,000 molecular weight PS. Large film square ( ) = 3.1, = 3.3%. Small film square (A)  

---

It is possible to make models which give microscopic meaning to the Weibull parameter 8 of the statistical description of fibril breakdown given in Eq. (31), or the related fibril stability — e. The necessary inputs are values for Pg CSi) which is defined as the P at a craze stress corresponding to a plastic strain e = 1. Modi-... 

---