In this paper, a comparative study on the fracture toughness of woven glass fibre reinforced polypropylene, chopped glass fibre reinforced polypropylene and nanoclay filled polypropylene composites is presented. Nanoc...In this paper, a comparative study on the fracture toughness of woven glass fibre reinforced polypropylene, chopped glass fibre reinforced polypropylene and nanoclay filled polypropylene composites is presented. Nanoclays (Cloisite 15A) of 1 wt. % to 5 wt. % were filled in polypropylene (PP) matrix and they were subjected to fracture toughness stu-dies. The specimen with 5 wt. % nanoclay showed 1.75 times and 3 times improvement in critical stress intensity factor (KIC) and strain energy release rate (GIC), respectively, over virgin PP. On the other hand, 3 wt. % nanoclay PP composites showed superior crack containment properties. These structural changes of composite specimens were examined using Transmission Electron Microscopy (TEM) and X-ray diffraction (XRD) methods. It showed that exfoli-ated nanocomposite structures were formed up to 3 wt. % nanoclay, whereas, intercalated nanocomposite structures formed above 3 wt. % nanoclay in the PP matrix. Furthermore, the woven fibre reinforced PP composites demonstrated superior crack resistant properties than that of clay filled nanocomposites and chopped fibre PP composites. However, KIC and GIC values for woven fibre composites were lesser than that of chopped fibre composites. Moreover, KIC and GIC values for both nanoclay filled PP composites and woven fibre composites are comparable even though the clay filled PP demonstrated catastrophic failure. Also, the crack propagation rate of PP-nanoclay composites is comparable to that of chopped fibre composites.展开更多
To develop parts, made of short glas fibre reinforced (sgfr) polymers for industrial purposes, a comprehensive material knowledge is necessary. Especially the material behaviour under cyclic loads has a great influenc...To develop parts, made of short glas fibre reinforced (sgfr) polymers for industrial purposes, a comprehensive material knowledge is necessary. Especially the material behaviour under cyclic loads has a great influence on the life time of parts. Parts are often used under complex load cases (stress state, temperature, ...), therefore it is indispensable to understand the effect of the main influence factors. High loads within load histories as well as stress concentrations can lead to plastic deformations. To cover this in an early stage of the development process, a closed simulation chain should be established. Therefore, the applicability of common material models (e.g. fatigue criteria according to Ramberg-Osgood) has to be studied first, the models have to be adapted or even new models have to be found for sgfr materials. This work focuses on the applicability of strain controlled cyclic tests for glass fibre reinforced polymers. Hereby the cyclic stress rearrangement in the low cycle regime of the S/N-curve can be described. Therefore, tests were performed on a 50 wt% sgfr partial aromatic polyamide. For the fatigue tests un-notched, injection moulded specimen were used. The tests show a principal applicability of strain controlled LCF-tests for sgfr polymers.展开更多
文摘In this paper, a comparative study on the fracture toughness of woven glass fibre reinforced polypropylene, chopped glass fibre reinforced polypropylene and nanoclay filled polypropylene composites is presented. Nanoclays (Cloisite 15A) of 1 wt. % to 5 wt. % were filled in polypropylene (PP) matrix and they were subjected to fracture toughness stu-dies. The specimen with 5 wt. % nanoclay showed 1.75 times and 3 times improvement in critical stress intensity factor (KIC) and strain energy release rate (GIC), respectively, over virgin PP. On the other hand, 3 wt. % nanoclay PP composites showed superior crack containment properties. These structural changes of composite specimens were examined using Transmission Electron Microscopy (TEM) and X-ray diffraction (XRD) methods. It showed that exfoli-ated nanocomposite structures were formed up to 3 wt. % nanoclay, whereas, intercalated nanocomposite structures formed above 3 wt. % nanoclay in the PP matrix. Furthermore, the woven fibre reinforced PP composites demonstrated superior crack resistant properties than that of clay filled nanocomposites and chopped fibre PP composites. However, KIC and GIC values for woven fibre composites were lesser than that of chopped fibre composites. Moreover, KIC and GIC values for both nanoclay filled PP composites and woven fibre composites are comparable even though the clay filled PP demonstrated catastrophic failure. Also, the crack propagation rate of PP-nanoclay composites is comparable to that of chopped fibre composites.
文摘To develop parts, made of short glas fibre reinforced (sgfr) polymers for industrial purposes, a comprehensive material knowledge is necessary. Especially the material behaviour under cyclic loads has a great influence on the life time of parts. Parts are often used under complex load cases (stress state, temperature, ...), therefore it is indispensable to understand the effect of the main influence factors. High loads within load histories as well as stress concentrations can lead to plastic deformations. To cover this in an early stage of the development process, a closed simulation chain should be established. Therefore, the applicability of common material models (e.g. fatigue criteria according to Ramberg-Osgood) has to be studied first, the models have to be adapted or even new models have to be found for sgfr materials. This work focuses on the applicability of strain controlled cyclic tests for glass fibre reinforced polymers. Hereby the cyclic stress rearrangement in the low cycle regime of the S/N-curve can be described. Therefore, tests were performed on a 50 wt% sgfr partial aromatic polyamide. For the fatigue tests un-notched, injection moulded specimen were used. The tests show a principal applicability of strain controlled LCF-tests for sgfr polymers.
