Comparison of J-integral methods for the characterization of tough polypropylene grades close to the glass transition temperature

• Published in: Engineering fracture mechanics 2018-11, Vol.203, p.2-17
• Main Authors: Gosch, Anja, Arbeiter, Florian J., Berer, Michael, Pinter, Gerald
• Format: Article
• Language: English
• Subjects: Data reduction; Fracture mechanics; Fracture surfaces; Fracture toughness; Glass; Glass transition temperature; J integral; Mechanical properties; Polypropylene; Surface layers; Temperature
• ISSN: 0013-7944; 1873-7315
• DOI: 10.1016/j.engfracmech.2018.06.002

•Multi-specimen method and load separation method lead to high data scattering.•By using the correction procedures the data scattering can be reduced.•The statistical Weibull analysis provided an initiation toughness parameter J0,th.•The ms-parameter gave information about the uniformity of the crack growth process.•A combination of several methods close to the glass transition temperature is recommended. The fracture mechanical characterization of very tough Polypropylene at room temperature is of great interest for many technical applications. Precision and validity of obtained values can significantly be influenced by notching and crack length determination, which has thoroughly been shown in literature. Additionally, the proximity to the glass transition temperature can induce further uncertainties. The aim of this study is to compare different J-integral methods of elastic plastic fracture mechanics to determine J-R curves for tested materials. Methods consist of the classical multi-specimen, a single specimen method (load separation) and a statistical approach (Weibull). Specific data reduction procedures based on physical principles were applied to reduce scattering and achieve reliable values. In this way, a reliable fracture mechanics characterization of Polypropylene at room temperature was achieved with a critical verification of the used methods. Finally, the determined fracture toughness value showed a good agreement with the surface texture of inspected fracture surfaces.