Prediction of the Fiber Orientation State and the Resulting Structural and Thermal Properties of Fiber Reinforced Additive Manufactured Composites Fabricated Using the Big Area Additive Manufacturing Process

Abstract

Recent advances in Fused Filament Fabrication (FFF) include large material deposition rates and the addition of chopped carbon fibers to the filament feedstock. During processing, the flow field within the polymer melt orients the fiber suspension, which is important to quantify as the underlying fiber orientation influences the mechanical and thermal properties. This paper investigates the correlation between processing conditions and the resulting locally varying thermal-structural properties that dictate both the final part performance and part dimensionality. The flow domain includes both the confined and unconfined flow indicative of the extruder nozzle within the FFF deposition process. The resulting orientation is obtained through two different isotropic rotary diffusion models, the model by Folgar and Tucker and that of Wang et al., and a comparison is made to demonstrate the sensitivity of the deposited bead's spatially varying orientation as well as the final processed part's thermal-structural performance. The results indicate the sensitivity of the final part behavior is quite sensitive to the choice of the slowness parameter in the Wang et al. model. Results also show the need, albeit less than that of the choice of fiber interaction model, to include the extrudate swell and deposition within the flow domain.

The effective thermal conductivity of double-reinforced composites

“…The parameters for both models could be estimated again from CFD-type simulations, see [24], or directly from material samples e.g. from microsection images.…”

Analysis and Evaluation of Fiber Orientation Reconstruction Methods

“…Even in the work by Férec et al [27], in which the Fokker-Planck equation is solved, the fiber orientation tensors and not the ODF were used as evaluation criteria. Russel et al investigated the prediction of the fiber orientation tensor in fused filament fabrication [28], while Kuhn et al in compression molding of long fibers.…”

“…Mathematically speaking, the reconstruction problem is ill-posed. orientation tensor in fused filament fabrication [28], while Kuhn et. al.…”

Editorial for the Special Issue on Discontinuous Fiber Composites

“…The processing of discontinuous fiber-reinforced composites, such as mold filling in injection molding, or flow through the nozzle during fused filament fabrication, has a profound impact on the arrangement of the fibers within the finished part. As fiber filled polymers are shaped into the final part geometry, the fibers are not only oriented [2,3,[7][8][9][10][11], but they are also broken down [4] and agglomerated [12], resulting in highly anisotropic products. While the anisotropy can be beneficial, when the fibers are aligned in the direction of highest stresses, most design processes of discontinuous fiber-reinforced composites parts do not consider all aspects of the process-microstructure-property relationship.…”

“…While the anisotropy can be beneficial, when the fibers are aligned in the direction of highest stresses, most design processes of discontinuous fiber-reinforced composites parts do not consider all aspects of the process-microstructure-property relationship. Several papers in this issue relate mechanical properties to fiber microstructure [1][2][3]5,7,9,10] and the paper by Wang and Smith [10] relate the microstructure to rheological behavior. Not incorporating the effect of fiber microstructure can result in larger safety factors, which leads to higher weight than necessary, limiting the application of this class of materials.…”