Numerical Modelling of Material Flow in the Resin-injection Pultrusion Process

Michael Sandberg*

*Corresponding author for this work

Research output: Book/ReportPh.D. thesis

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Abstract

This PhD thesis concerns resin-injection pultrusion (RIP), a low-cost and continuous process to mass-produce fibre-reinforced polymer composite profiles. The thesis follows a clear trend in modern manufacturing engineering (Industry 4.0) that is to exploit simulation models to analyse processesing steps. This work represents the state of the art of simulating material flow in RIP processes.

The thesis first presents pultrusion in a societal and economic context, followed by a short overview of related literature. Then, the conservation equations that govern the material flow (mass, momentum, or energy) are derived and applied to RIP processes. The theoretical background is given with a focus on steady-state modelling of the coupled physics (multiphysics) that take place inside the pultrusion die. The impregnation flow is considered to be single-phased and characterised by Darcy’s law. To analyse flow-induced fibre compaction, resin flow in a compliant porous medium is introduced as well. In this relation, the thesis also presents material characterisation methodologies to measure permeability and compaction behaviour. To model the resin flow front, both Eulerian (that utilise a level-set) and arbitrary Lagrangian-Eulerian (ALE) methods are introduced. Nonisothermal flow in a compliant porous medium is presented, and finally, a steady-state and Eulerian approach is introduced to model process induced stress and deformation.

Numerical and experimental results are presented in seven appended publications that reflect different aspects of the material flow in RIP processes. First, a new level-set method to model the resin flow front is presented. It is demonstrated how the framework tracks the flow front itself and can advance it with CFL-sized time. Using this level-set method, it is shown how RIP processes can utilise permeable areas to improve impregnation flow. Then, experimental material characterisation of pultrusion-specific glass fibre rovings is conducted. The experiments show that texturised rovings are more permeable and less compliant. Following this study, experimental and numerical analyses of the material flow in an industrial pultrusion line are conducted. It is demonstrated that the heating configuration, together with the strongly convective flow near inlets, give phase transitions that are both concave and convex-shaped. In addition, it is shown that fibre compaction remains largely unaffected by the magnitude of the injection pressure in the pultrusion line. Finally, in a theoretical case study, it is demonstrated that a steady-state, Eulerian approach enables 9-35 times faster computation times compared to the existing methods for analysis of process-induced stress and deformation.
Original languageEnglish
Place of PublicationKgs. Lyngby
PublisherTechnical University of Denmark
Number of pages265
ISBN (Electronic)78-87-7475-627-9
Publication statusPublished - 2020

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