Assessment Of Methods To Determine Fracture Toughness Of Polymers In The Ductile-To-Brittle Transition Region

R. COCCO; P. FRONTINI; J. PEREZ IPIÑA

Turín, Italia

Conferencia; ICF11; 2005

The fracture behaviour of materials in the ductile-to-brittle region is neither completely brittle nor entirely ductile. Besides, scatter in toughness results has been reported in polypropylene and nylon. At the moment there is no general agreement on the methodology to determine the fracture toughness in the transition region. In this work an assessment of different proposed methods based on LEFM, EPFM and statistical approach was carried out over two materials: polypropylene homopolymer (PPH) and a blend of PPH containing 20 wt.% of elastomeric polyolefin (PPH/POes). The methods analysed were Fernando- Williams method, plastic zone corrected LEFM proposed by Gerin et al., GST /GINST method by V-Khanh and De Charentay, JR curve method by Santarelli et al., and a statistical approach proposed by the authors in a previous work. The results of this analysis indicate that the Fernando-Williams and Plastic zone corrected LEFM methods, based on LEFM, tended to underestimate the fracture toughness, being very conservative. On the other side, JR method may overestimate the toughness, as in PPH/POes blend case. The GST /GINST and Statistical methods appear to be the most adequate to characterise the fracture toughness of PPH and PPH/POes blend. The values of the characteristic fracture toughness found by both methods were slightly smaller than the minimum determined experimentally and proved very close between themselves