No abstract

No abstract

This article deals with the influence of the polymeric matrix, such as isotactic polypropylene (iPP), polyethylene (PE-HD), and isotactic polybutene-1 (iPB-1), and the glass fiber content on the material behavior of short glass fiber reinforced thermoplastics. The glass fiber content of all materials ranged between 0 and 50 wt %, which corresponds to a volume content between 0 and approx. 0.264. To describe the mechanical properties of all materials, the stiffness, strength, hardness, and toughness behavior were determined. The crack toughness behavior regarding unstable crack propagation was also assessed by applying fracture mechanics concepts. It was found that the energy-determined J-values for the PP material system reach their maximum at a glass fiber content of 0.135. In contrast, the crack toughness of the PE-HD materials increases continuously with increasing glass fiber content due to the unchanged deformation ability at simultaneously increasing strength. The toughness level of the PB-1 materials is nearly the same independent of the glass fiber content due to the opposite trend of the load and the deformation ability.

No abstract

Summary The Stepped Isothermal Method (SIM) is a relatively new method for accelerated determination of the creep behaviour of polymers. The need for such a new method arises from the fact that for modern plastic components such as pipe systems minimum lifetimes of 50 years and more are achieved. The analysis of creep applying conventional methods of testing over such long periods of time is not reasonable from an economic point of view. This forms the basis for the development of accelerated procedures such as SIM. Plastic components can exhibit creep characteristics to be a function of the position due to processing. Such position‐dependent creep behaviour cannot be imaged by volume‐sensitive creep tests such as SIM under uniaxial tensile load. Therefore, SIM was implemented by means of recording macroindentation to characterize the local long‐time creep behaviour and the expressiveness of this method for different polypropylene materials was shown in this study.