Thermal Effects in the Numerical Simulation of the Thermoforming of Multilayered Polymer Sheets
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M. Bellet
Abstract
This paper mainly treats the thermal effects during the thermoforming process while most of the previous analyses consider an isothermal deformation. A non isothermal three dimensional finite element model of the thermoforming process is proposed. It couples the thermal equations in the thickness and mechanical equations on the mean surface of the sheet. The mechanical resolution is done by a finite element method using a membrane approximation. The deformation is driven by a pressure difference through the sheet. The thermal resolution uses a one dimension finite element method in the thickness with convection or conduction at the surface and dissipation of mechanical energy. The polymer cooling is very efficient during the contact with the tools. The coupling is done by the thermal dependent rheology. The respective contributions of friction and thermal effects in the thickness of the part during the process are discussed. The model also considers a possible multilayered material, with specific rheological parameters inside each layer. The rheology of a polystyrene was measured under elongation as a function of temperature, strain and strain-rate and described by a viscoplastic law. The predictions of the model were compared with measurements on an instrumented thermoforming machine and with the local thickness of axisymmetrical parts and with 3-D parts thermoformed with the same polystyrene.
© 1998, Carl Hanser Verlag, Munich
Articles in the same Issue
- Contents
- Contents
- Editorial
- Third in a Series: Pioneers of Polymer Processing Charles Hancock — The First Thermoplastics Processing Innovator
- Internal Mixers
- Finite Element Analysis of Mixing in Partially Filled Twin Blade Internal Mixers
- Screw Extrusion
- Use of Dye Containing Polymeric Microcapsules for Determining Shear Stresses
- Modeling Flow and Fusion of Mixtures/Blends of Polymer Pellets and a Low Viscosity Phase in a Modular Co-rotating Twin Screw Extruder
- Fiber and Film
- Development of High Quality LLDPE and Optimised Processing for Film Blowing
- Molding
- Impregnating Flow of a Rheokinetic Liquid
- Morphology of Injection Molded Polyacetal during Filling
- Crystal Orientation in Injection Moldings of Talc-filled Polyolefins
- Structure and Properties of Injection Moldings of β-Crystal Nucleator-added PP
- Thermal Effects in the Numerical Simulation of the Thermoforming of Multilayered Polymer Sheets
- Measurement and Prediction of Anisotropy in Injection Moulded PP Products
- Rapid Communication
- Gas Penetrations in Symmetrical Tapping Ribs during Gas-Assisted Injection Molding
Articles in the same Issue
- Contents
- Contents
- Editorial
- Third in a Series: Pioneers of Polymer Processing Charles Hancock — The First Thermoplastics Processing Innovator
- Internal Mixers
- Finite Element Analysis of Mixing in Partially Filled Twin Blade Internal Mixers
- Screw Extrusion
- Use of Dye Containing Polymeric Microcapsules for Determining Shear Stresses
- Modeling Flow and Fusion of Mixtures/Blends of Polymer Pellets and a Low Viscosity Phase in a Modular Co-rotating Twin Screw Extruder
- Fiber and Film
- Development of High Quality LLDPE and Optimised Processing for Film Blowing
- Molding
- Impregnating Flow of a Rheokinetic Liquid
- Morphology of Injection Molded Polyacetal during Filling
- Crystal Orientation in Injection Moldings of Talc-filled Polyolefins
- Structure and Properties of Injection Moldings of β-Crystal Nucleator-added PP
- Thermal Effects in the Numerical Simulation of the Thermoforming of Multilayered Polymer Sheets
- Measurement and Prediction of Anisotropy in Injection Moulded PP Products
- Rapid Communication
- Gas Penetrations in Symmetrical Tapping Ribs during Gas-Assisted Injection Molding
