Title: Stiffness Prediction and Validation of Large Volume 3D Printed, Short-Fiber-Filled Polymer Composites
Authors: Timothy Russell and David A. Jack
Abstract: Large-volume 3D deposition of short carbon fiber filled (CFF) thermoplastic composites greatly enhances the value and potential of additive manufacturing by offering fast production of large-scale tooling and even large-scale, end-use parts. Validated models to predict the material properties as a function of processing parameters of such 3D printed composites aid in driving down the design cost of a production part by eliminating the need to process large volumes of material in trial prints and the subsequent final product characterization. In this study, a method of predicting the effective elastic modulus from the flow simulation to the final deposition and cooling of a short fiber filled deposited structure is presented. Specifically, a 13% CFF acrylonitrile butadiene styrene (ABS) is considered. An in-house, large volume 3D printer was built and used to print tensile bars that were tested based off ASTM-D3039. Modeling was carried out using a custom MATLAB code to model the fiber orientation state along the velocity field streamlines within the nozzle, the die-swell of the extrudate, and the subsequent deposition onto the moving platen. The resulting predicted fiber orientation state is then coupled with micromechanical modeling to obtain a spatially varying anisotropic stiffness tensor. This result is then used within a finite element model with spatial varying stiffness to mimic the effective stiffness of the processed composite. Modeling results indicate little difference between a fully filled deposition (i.e., no interlaminar voids between deposition beads) and the actual cross-sectioned geometry. The results obtained from the RSC fiber interaction model for a value of κ=1/30 and C_I=0.03 were in the best agreement with the experimental testing with a differential of less than 20% between experiment and modeling, and future work will be required to better characterize the flow parameters before the modeling efforts can be considered fully validated.
References:  Post, B., Richardson, B., Lloyd, P., Love, L., Nolet, S., and Hannan, J., 2017, Additive Manufacturing of Wind Turbine Molds, ORNL/TM--2017/290, CRADA/NFE-16-06051, 1376487.  “Shelby Cobra” [Online]. Available: https://web.ornl.gov/sci/manufacturing/shelby/. [Accessed: 20-Jan-2019].  “ORNL 3D-Printed Shelby Cobra,” Innovations in Manufacturing [Online]. Available: http://web.ornl.gov/sci/manufacturing/media/news/detroit-show/index.shtml. [Accessed: 03-Feb-2019].  Jeffery George Barker, and Filon Louis Napoleon George, 1922, “The Motion of Ellipsoidal Particles Immersed in a Viscous Fluid,” Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character, 102(715), pp. 161–179.  Folgar, F., and Tucker, C. L., 1984, “Orientation Behavior of Fibers in Concentrated Suspensions,” Journal of Reinforced Plastics and Composites, 3(2), pp. 98–119.  Phelps, J. H., and Tucker, C. L., 2009, “An Anisotropic Rotary Diffusion Model for Fiber Orientation in Short- and Long-Fiber Thermoplastics,” Journal of Non-Newtonian Fluid Mechanics, 156(3), pp. 165–176.  Wang, J., O’Gara, J. F., and Tucker, C. L., 2008, “An Objective Model for Slow Orientation Kinetics in Concentrated Fiber Suspensions: Theory and Rheological Evidence,” Journal of Rheology, 52(5), pp. 1179–1200.  Huynh, H. M., 2001, “Improved Fiber Orientation Predictions for Injection-Molded Composites,” University of Illinois at Urbana-Champaign.  Russell, T., Heller, B., Jack, D. A., and Smith, D. E., 2018, “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,” Journal of Composites Science, 2(2), p. 26.  Advani, S. G., and Tucker, C. L., 1987, “The Use of Tensors to Describe and Predict Fiber Orientation in Short Fiber Composites,” Journal of Rheology, 31(8), pp. 751–784.  Tandon, G. P., and Weng, G. J., 1984, “The Effect of Aspect Ratio of Inclusions on the Elastic Properties of Unidirectionally Aligned Composites,” Polymer Composites, 5(4), pp. 327–333.  Cintra, J. S., and Tucker, C. L., 1995, “Orthotropic Closure Approximations for Flow‐induced Fiber Orientation,” Journal of Rheology, 39(6), pp. 1095–1122.  Verweyst, B. E., and Tucker, C. L., 2002, “Fiber Suspensions in Complex Geometries: Flow/Orientation Coupling,” The Canadian Journal of Chemical Engineering, 80(6), pp. 1093–1106.  “Precision Plasma LLC” [Online]. Available: http://precisionplasmallc.com/. [Accessed: 03-Feb-2019].  “Strangpresse Extruders | Strangpresse.”  Heller, B. P., Smith, D. E., and Jack, D. A., “SIMULATION OF PLANAR DEPOSITION POLYMER MELT FLOW AND FIBER ORIENTAITON IN FUSED FILAMENT FABRICATION,” p. 16.  Heller, B. P., Smith, D. E., and Jack, D. A., 2016, “Effects of Extrudate Swell and Nozzle Geometry on Fiber Orientation in Fused Filament Fabrication Nozzle Flow,” Additive Manufacturing, 12, pp. 252–264.  Zhang, D., E. Smith, D., A. Jack, D., and Montgomery-Smith, S., 2011, “Numerical Evaluation of Single Fiber Motion for Short-Fiber-Reinforced Composite Materials Processing,” J. Manuf. Sci. Eng, 133(5), pp. 051002-051002–9.
Conference: SAMPE 2019 - Charlotte, NC
Publication Date: 2019/05/20
Price: FREEGet This Paper