Transactions of Materials Processing (소성∙가공)

The Korean Society for Technology of Plasticity and materials processing (한국소성∙가공학회)
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Numerical and Experimental Analysis of Laminated-Film Thickness Variation in Vacuum-Assisted Thermoforming

열진공성형에서 적층필름 두께변화에 대한 수치 및 실험적 해석

  • Lee, H.S. (Dept. Aeronautical & Mechanical Design Eng., Korea Nat'l Univ. Transportation) ;
  • Yoo, Y.G.
  • Received : 2013.04.08
  • Accepted : 2013.05.23
  • Published : 2013.06.01
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Abstract

Vacuum-assisted thermoforming is one of the critical steps for successful application of film insert molding (FIM) to make parts of complex shape. If the thickness distribution of the formed film is non-uniform, then cracking, deformation, warpage, and wrinkling can easily occur at the injection molding stage. In this study, the simulation of thermoforming was performed to predict the film thickness distribution, and the results were compared with experiments. Uniaxial tensile tests with a constant crosshead speed for various high temperatures were conducted to investigate the stress-strain behavior. An instance of yielding occurred at the film temperature of $90^{\circ}C$, and the film stiffness increased with increasing crosshead speed. Two types of viscoelastic models, G'Sell model, K-BKZ model, were used to describe the measured stress-strain relationship. The predicted film thickness distributions were in good agreement with the experimental results.

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References

  1. E. Gimenez, J. M. Lagaron, L. Cabedo, R. Gavara, J. J. Saura, 2004, Study of the Thermoformability of Ethylene-vinyl Alcohol Copolymer Based Barrier Blends of Interest in Food Packaging Applications, J. Appl. Poly. Sci., Vol. 96, No. 6, pp. 3851-3855.
  2. E. Gimenez, J. M. Lagaron, M. L. Maspoch, L. Cabedo, J. J. Saura, 2004, Uniaxial Tensile Behavior and Thermoforming Characteristics of High Barrier EVOH-Based Blends of Interest in Food Packaging, Polym. Eng. Sci., Vo. 44, No. 3, pp. 598-608. https://doi.org/10.1002/pen.20054
  3. S. Poller, W. Michaeli, 1992, Film Temperatures Determine the Wall Thickness of Thermoformed Parts, SPE ANTEC, Vol. 38, No. 1 , pp. 104-108.
  4. A. Aroujallan, M. O. Ngadi, J. P. Emond, 1997, Wall Thickness Distribution in Plug-assist Vacuum Formed Strawberry Containers, Polym. Eng. Sci., Vol. 37, No. 1, pp. 178-182. https://doi.org/10.1002/pen.11659
  5. S. C. Chen, S. T. Huang, M. C. Lin, R. D. Chien, 2008, Study on the Thermoforming of PC Films Used for In-Mold Decoration, Int. Commun. Heat Mass Transfer, Vol. 35, No. 8, pp. 967-973. https://doi.org/10.1016/j.icheatmasstransfer.2008.04.008
  6. G. Kim, K. Lee, S. Kang, 2009, Prediction of the Film Thickness Distribution and Pattern Change during Film Insert Thermoforming, Polym. Eng. Sci., Vol. 49, No. 11, pp. 2195-2203. https://doi.org/10.1002/pen.21467
  7. J. K. Lee, T. L. Virkler, C. E. Scott, 2001, Effects of Rheological Properties and Processing Parameters on ABS Thermoforming, Polym. Eng. Sci., Vol. 41, No. 2, pp. 240-261. https://doi.org/10.1002/pen.10725
  8. J. K. Lee, T. L. Virkler, C. E. Scott, 2001, Influence of Initial Sheet Temperature on ABS Thermoforming, Polym. Eng. Sci., Vol. 41, No. 10, pp. 1830-1844. https://doi.org/10.1002/pen.10880
  9. Y. G. Yoo, H. S. Lee, 2011, Effects of Processing Conditions on Thickness Distribution for a Laminated Film during Vacuum-Assisted Thermoforming, Trans. Mater. Process., Vol. 20, No. 3, pp. 250-256. https://doi.org/10.5228/KSTP.2011.20.3.250
  10. C. G'Sell, J. J. Jonas, 1979, Determination of the Plastic Behaviour of Solid Polymers at Constant True Strain Rate, J. Mater. Sci., Vol. 14, No. 3, pp. 583-591.
  11. C. G'Sell, N. A. Aly-Helal, J. J. Jonas, 1983, Effect of Stress Triaxiality on Neck Propagation during the Tensile Stretching of Solid Polymers, J. Mater. Sci., Vol. 18, No. 6, pp. 1731-1742. https://doi.org/10.1007/BF00542069
  12. C. G'Sell, N. A. Aly-Helal, S. L. Semiatin, J. J. Jonas, 1992, Influence of Deformation Defects on the Development of Strain Gradients during the Tensile Deformation of Polyethylene, Polym., Vol. 33, No. 6, pp. 1244-1254. https://doi.org/10.1016/0032-3861(92)90770-W
  13. B. Bernstein, E. A. Kearsley, L. J. Zapas, 1965, A Study of Stress Relaxation with Finite Strain, Rubber Chem. Technol., Vol. 38, No. 1, pp. 76-89. https://doi.org/10.5254/1.3535640
  14. Acuuform, 2005, Computer Simulations of Transforming and Blowing Molding, http://www.t-sim.com/index.html.
  15. M. H. Wagner, 1976, Analysis of Time-Dependent Non-Linear Stress-Growth Data for Shear and Elongational Flow of a Low-Density Branched Polyethylene Melt, Rheol. Acta., Vol. 15, No. 2, pp. 136-142. https://doi.org/10.1007/BF01517505

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