On the Determination of Fracture Toughness of PP Polymers

ALICIA SALAZAR; L.A. FASCE,; J. RODRÍGUEZ; P. M. FRONTINI

Ottawa

Conferencia; 12 th. International Conference of Fracture; 2009

The fracture behavior of Polypropylene polymers is rather controversial since is neither completely brittle nor entirely ductile. Scatter in toughness results and difficulty in distinguishing the amount of stable crack growth impair the situation. Consequently, conventional methods based exclusively either on linear elastic fracture mechanics theory (LEFM) or on non-linear elastic fracture mechanics theory (NLEFM) are not suitable. It was demonstrated by Cocco et al in 2005, that Weibull statistical method could be successfully used to determine the toughness of polymers displaying ductile-to-brittle behavior. On the other side,when the amount of stable crack growth was not easy to distinguish on fracturesurface, it was also argued in literature that a Jc value may be determined using the stress whitening method suggested by Zhang et al in 1989. The present study compares the PP toughness values determined by the statistical approach and the stress whitening method. It also discusses the reliability of both values and the advantages and drawbacks of each methodology