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

Abstract

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.