Efficient bead-chain model for predicting fiber motion during molding of fiber-reinforced thermoplastics

Sasayama, Toshiki; Inagaki, Masahide

doi:10.1016/j.jnnfm.2018.10.008

Cited by 14 publications

(8 citation statements)

References 25 publications

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“…Therefore, a prediction of the particle orientation after an extrusion process is the topic of ongoing research. However, while there exist a burgeoning number of analytical orientation prediction models (OPMs) [ 3 , 4 , 5 , 6 , 7 , 8 ] or microscopic simulations [ 9 , 10 , 11 ] to predict such a particle orientation within the still-wet filament, little is known about the magnitude of particle reorientation in robocasted filaments during the drying step. Experimentally, information on particle reorientation is difficult to address as the particle orientation can only be measured after the sintering step, before which, however, the liquid phase must have already been removed.…”

Section: Introductionmentioning

confidence: 99%

Reorientation of Suspended Ceramic Particles in Robocasted Green Filaments during Drying

et al. 2022

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This work considers the fabrication of ceramic parts with the help of an additive manufacturing process, robocasting, in which a paste with suspended particles is robotically extruded. Within the final part, the material properties depend on the orientation of the particles. A prediction of the particle orientation is challenging as the part usually undergoes multiple processing steps with varying contributions to the orientation. As the main contribution to the final particle orientation arises from the extrusion process, many corresponding prediction models have been suggested. Robocasting involves, however, further processing steps that are less studied as they have a smaller influence on the orientation. One of the processing steps is drying by natural convection, which follows directly after the extrusion process. A quantification of the reorientation that occurs during drying is mostly unknown and usually neglected in the models. Therefore, we studied the amount of reorientation of suspended particles in robocasted green filaments during drying in detail. For our study, we applied the discrete element method, as it meets various requirements: The exact particle geometry can be resolved precisely; particle–particle interactions can be described; the paste composition is reproduced exactly; the initial particle orientation can be set in accordance with the prediction from the analytical models for the extrusion part; macroscopic force laws exist to represent capillary forces due to the remaining fluid phase that remains during drying. From our study, we concluded that the magnitude of particle reorientation during drying is small compared to the orientation occurring during the extrusion process itself. Consequently, reorientation during drying might further be neglected within analytical orientation prediction models.

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Section: Introductionmentioning

confidence: 99%

Reorientation of Suspended Ceramic Particles in Robocasted Green Filaments during Drying

et al. 2022

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“…The LFRT pellets used for injection molding usually have an initial fiber length of 10–25 mm, but the strong friction shear between fibers and matrix, the interaction between fibers and processing equipment and the intertwining of fibers and fibers may severely reduce fiber length, resulting in fibers of this initial length rarely survive in injection molded parts. 8,25–27…”

Section: Introductionmentioning

confidence: 99%

“…1,14,24 The LFRT pellets used for injection molding usually have an initial fiber length of 10-25 mm, but the strong friction shear between fibers and matrix, the interaction between fibers and processing equipment and the intertwining of fibers and fibers may severely reduce fiber length, resulting in fibers of this initial length rarely survive in injection molded parts. 8,[25][26][27] Bailey and Kraft found that the breakage of long fibers mainly occurred in the plasticizing stage before the polymer melt entered the mold. 28 Therefore, in most experimental studies, fiber length attrition was considered as a function of process parameters such as screw back pressure, injection speed, and nozzle design.…”

Section: Introductionmentioning

confidence: 99%

An effective model for fiber breakage prediction of injection-molded long fiber reinforced thermoplastics

Kang

Huang

Zhang

et al. 2020

Journal of Reinforced Plastics and Composites

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Fiber length is an important factor affecting the mechanical properties of long fiber reinforced thermoplastic (LFRT). When LFRT is processed by injection molding, the strong shear flow usually leads to severe fiber breakage. Therefore, it is a crucial issue to reduce the loss of fiber length as much as possible during composite molding. Current work focused on constructing an effective model for predicting fiber breaking caused by shear stress during melt filling. Based on the Oseen formula, the disturbance of liquid flow caused by a single external force was studied, and the force acceptance formula of fiber immersed in flow field was derived. A mechanical model for characterizing the degree of fibers buckling and breaking and the shear stress was constructed by the Euler buckling criterion. To verify the model, glass fiber reinforced polypropylene (GF/PP) composites with initial fiber length of 3 mm and 6 mm was subjected to shear at the specific shear rate by using a rotating rheometer. The length of GF after sheared was measured by fiber length distribution analyser. The breaking ratio of fibers was predicted using the new model, and the predicted results were in good agreement with experiment, although more comparisons with experiments are necessary.

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“…In this panorama, the possibility to implement an accurate and reliable solver is a good opportunity to study the evolution of complex fluids in complex systems. Different models have already been developed by referring to traditional Navier–Stokes (NS) environment [7–9], and they span a large number of applications or phenomenological analyses. For example, many studies have been focused on the analysis of fluid instability in suddenly expanded/contracted channels by recalling the Coanda effect, [3,10–12], or they have focused on the analysis of convection [13,14].…”

Section: Introductionmentioning

confidence: 99%

A lattice-Boltzmann free surface model for injection moulding of a non-Newtonian fluid

Chiappini

2020

Phil. Trans. R. Soc. A.

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The aim of this work is to present a lattice Boltzmann (LB) model devoted to dealing with non-Newtonian free surface flow. The combination of LB solver with a free-surface model allows dealing with multiphase flows where the density ratio in between the two considered phases is so high that the lighter phase can be neglected. For this particular set of multiphase models, the interface between the two phases is numerically reconstructed and transported via a diffusion equation. Moreover, the application of a Carreau approach for viscosity modelling allows the introduction of effects related to shear stress on fluid flow evolution. Two different non-Newtonian silicon-like materials have been considered here, namely the polystyrene and acrylonitrile butadiene styrene. Here, the author, after the mandatory model validation with a reference configuration, presents some applications of injection moulding for two different test-cases: the former is the injection in a labyrinth-like gasket, whereas the latter is the injection in a porous media. This article is part of the theme issue ‘Fluid dynamics, soft matter and complex systems: recent results and new methods’.

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Efficient bead-chain model for predicting fiber motion during molding of fiber-reinforced thermoplastics

Cited by 14 publications

References 25 publications

Reorientation of Suspended Ceramic Particles in Robocasted Green Filaments during Drying

Reorientation of Suspended Ceramic Particles in Robocasted Green Filaments during Drying

An effective model for fiber breakage prediction of injection-molded long fiber reinforced thermoplastics

A lattice-Boltzmann free surface model for injection moulding of a non-Newtonian fluid

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