Rheology of natural fibers thermoplastic compounds: Flow length and fiber distribution

Ramzy, Amna; Elsabbagh, Ahmed; Steuernagel, Leif; Ziegmann, Gerhard; Meiners, Dieter

doi:10.1002/app.39861

Cited by 22 publications

(18 citation statements)

References 24 publications

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“…The fiber content also increased linearly with the distance from the injection gate (Figure 5), that is, from 21% at the cavity entry (10 mm from the gate) to approximately 26% in the near-end-of-fill region (265 mm). This increase is in accordance with the trend previously observed by Ramzy et al who studied the behavior of PP reinforced with natural hemp fibers in a spiral flow mold [21]. For fillers of different types, Kubat and Szalanczi as well as Danès et al found a minimum close to the gate and a pronounced maximum at the opposite mold wall with glass spheres and aluminum fibers, respectively [17,35].…”

Section: Fiber Concentration Along the Flow Pathsupporting

confidence: 91%

Fiber Orientation and Concentration in an Injection-Molded Ethylene-Propylene Copolymer Reinforced by Hemp

et al. 2020

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This paper characterizes and analyzes the microstructures of injection-molded polypropylene parts reinforced with 20 wt% of hemp fibers in order to understand the process induced variations in thermomechanical properties. In-thickness fiber orientation and fiber content were determined by X-ray tomography along the flow. The fiber content along the flow path was also determined by direct fiber content measurements after matrix dissolution, showing an increase of 2%/100 mm for a 2.2 mm-thick plate due to fiber migration during the filling stage. A typical shell/core structure for fiber orientation in injection molding was observed, but with a very clear transition between the layer solidified under high shear rates and the core in which the fiber content was reduced by more than 50%. The orientation of hemp fibers is lower than the one of glass fibers, especially in thickness direction. However, the overall fiber orientation in the injection direction induces significant anisotropic thermomechanical properties, which cannot be explained by simple micromechanical models that consider isotropic mechanical properties for hemp fibers. These phenomena must be taken into account in process simulation codes for injection molding to better predict thermomechanical properties as well as part shrinkage and warpage to design molds.

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Section: Fiber Concentration Along the Flow Pathsupporting

confidence: 91%

Fiber Orientation and Concentration in an Injection-Molded Ethylene-Propylene Copolymer Reinforced by Hemp

et al. 2020

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“…Hemp fibers preserve higher aspect ratio, hence higher reinforcing, due to its fibrillation compared to flax. Ramzy et al [9] studied the flowability and fiber homogeneity of NFTC using hemp and sisal in spiral injection molds. Polymer temperature, mold temperature and injection pressure have positive effect on the measured spiral length.…”

Section: Introductionmentioning

confidence: 99%

Flowability and fiber content homogeneity of natural fiber polypropylene composites in injection molding

Elsabbagh¹,

Ramzy²,

Steuernagel³

et al. 2016

AIP Conference Proceedings

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Influence of rapid heat cycle molding and filler type on warpage of injection molded parts out of PP-based compounds AIP Conference Proceedings 1779, 020005 (2016) Abstract. As an index of viscosity, flowability of natural fiber polypropylene composites is assessed by spiral mold test using injection molding machine. The effect of the processing parameters like the injection temperature at 180-220°C, injection pressure at 500-1000 bar and the mold temperature of room temperature and 80°C on flowability is studied. The investigated parameters are the fiber shape (Non branched straight cellulose versus low flexural stiffness and branched hemp fibers), fiber length (0.5 versus 1.5 mm chopped cellulose fibers) and fiber content Wf (10 versus 30 wt%). The results show that the most significant parameters in a descending order are the pressure, temperature and the mold temperature. Another aspect of the product quality is the homogeneity of the fiber content through the whole injected spirals. Therefore samples are taken out at even distances along the spiral. The cut samples are dissolved to extract fibers and calculate the fiber content. Fiber content definition along the injected spirals proved that it is not constant and the deviation in its measurements can reach to almost 30% from the nominal value. The results prove the separation of fibers before being injected specially in cases of low pressure and low injection temperatures. Secondly, the fiber content varies in a cyclic way. The number of cycles increases with the increase of temperature and pressure but with smaller amplitude of variation. The variation of the fiber content in cellulose fluctuates around an almost constant value which is not the case with hemp variation. Thirdly, the fiber content shows in most of the cases a parabolic trend with a minimum point just shortly after the input injection point. Fourth, the change in fiber length behaves more or less like change in fiber content especially at both low pressure and temperature. Fifth, the variation in fiber content (Wfmax -Wfmin) along the spiral is clear in composites with hemp fibers at high processing temperature / pressure . These results about variation in fiber content are studied in terms of the measured fiber dimensions. Fiber length is defined by the dynamic image analysis system QICPIC. Fiber length proves that the longer the fiber length, most likely the higher the fiber content. However, these results are still in need to be deeply analyzed and better understood in order to open the door in future for robust simulation.

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“…The FMS-induced fiber content changes could be observed across the thickness direction and along large component regions. 6 It is influenced by many factors, including the confinement effect, 4 flow length, 6,7 fiber content, 4 and flow rate. 4 Under simple shear conditions, the fiber jamming effect could lead to a discontinuous shear thickening (DST) phenomenon for fiber-filled Newtonian fluid suspensions, 8 and dilatancy is often observed in conjunction with DST.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Role of confinement in the shear banding and shear jamming in noncolloidal fiber suspensions

Li,

You,

Liu

et al. 2023

Soft Matter

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Rheology of natural fibers thermoplastic compounds: Flow length and fiber distribution

Cited by 22 publications

References 24 publications

Fiber Orientation and Concentration in an Injection-Molded Ethylene-Propylene Copolymer Reinforced by Hemp

Fiber Orientation and Concentration in an Injection-Molded Ethylene-Propylene Copolymer Reinforced by Hemp

Flowability and fiber content homogeneity of natural fiber polypropylene composites in injection molding

Role of confinement in the shear banding and shear jamming in noncolloidal fiber suspensions

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