Dilatation band toughening effect

Importance of the Findings. The present work indicates that the formation of crazing and dilatation bands in moderately cross-linked engineering thermosets can be quite common. Therefore, it is important to determine whether crazing and dilatation bands are effective in toughening thermosets. It is equally important to find out how to promote these types of fracture mechanisms, either via modification of network architecture or incorporation of toughening agents. 

A. Lazzeri, The kinetics of dilatational bands and the interparticle distance effect in rubber toughened polymers, in Proc. 10th International Conference on Deformation, Yield and Fracture of Polymers, Cambridge, UK, The Institute of Materials, London, 1997, p. 442. 

In the first attemped quantitative model proposed by Lazzeri and Bucknall [52], it was predicted that only particles >0.25 p diameter were capable of cavitating imder a given set of conditions, lending some support to the concept that there is an optimum rubber particle size for the toughening. They also showed that cavitated rabber particles can initiate crazes and dilatational bands in the matrix. They propose that the sudden conversion of rubber particles into the mechanical equivalent of voids (by cavitation) has the indirect effect of accelerating the volume expansion in the matrix through the formation of dilatational shear bands. 

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