CFD Modeling of the Closed Injection Wet-Out Process For Pultrusion

More documents

Recommendations

Info

Flow Solver The mathematical model was solved by the flow solver ANSYS-CFX 11.0 with additional source terms added to account for the moving porous medium. RESULTS AND DISCUSSION Flow Patterns in the Injection Box Streamlines, created by releasing massless particles from the feed ports, show how the resin impregnates the fiber bundle in Figure 5. Resin injected through the feed ports spreads over the top of the bundle, then impregnates into it and finally is pulled through the injection box, achieving good wet-out. The streamlines are colored to indicate the pressure gradient. Pressure Profiles in the Injection Box Figure 6 shows the centerline pressure profiles in the injection box for different line speeds. As expected the final pressure rise increases with line speed. For example, at a line speed of 0.6 m/min, the pressure rise at the die face is 23 bar, rising to 57 bar at a line speed of 1.5 m/min. The experimental results (blue squares in Fig. 6) compare favorably with the CFD results at ~10 cm from the die face. However, the injection box pressure measured at ~2.5 cm from the die face is much higher than predicted. The model assumes a uniform reinforcement matrix and does not take into account factors such as roving twist or resin/fiber interactions which would likely be magnified in the constrained state near the die face. Further experimental work is in progress to verify and expand on these results. Figure 7 shows the influence of the viscosity of the resin, glass fraction, box length and box height (i.e., the effective taper angle of the box) on the final pressure rise in the injection box. As expected for a fully wet-out part, this relationship is linear for viscosity and box length. While the physics of the pressure rise are not completely understood, the model predicts nonlinear relationships for box height and glass fraction. The model can also look at the influence of other geometrical factors such as injection location(s) and other operating parameters including injection pressure on the pressure profiles in the box. Fiber Wet-Out in the Injection Box Figure 8 shows the resin flow-front development in the injection box. To achieve good wet-out, both flow fronts should reach the center of the fiber bundle but also spread to all regions of the injection box. In Figure 8, the resin is colored to indicate residence time in the box. It can be observed in this case that the pultruded part is completely wet-out by the time it enters the die. The model can be used to illustrate process conditions under which profile wet-out becomes an issue. It can also be used to evaluate the influence of injection box geometry and operating parameters such as injection pressure on wetting efficiency.
CONCLUSIONS A mathematical model of a pultrusion injection box has been created. A permeability model for unidirectional reinforcements based on porosity and direction has been used. The model can predict injection box pressure profiles and flow patterns giving an estimation of reinforcement wet-out. The model has proven to be versatile and can evaluate a number of factors influencing process performance including injection box geometry, the number and location of the injection ports, injection pressure, line speed, resin physical properties, fiber permeability and fiber fraction on pressure rise in the injection box. The model predicts the appropriate trends when compared with experimental data and experience. Further experimental work is planned to verify additional geometric and process variations. With the use of this model, the typical empirical approach taken with injection box development can be reduced or eliminated. Hence, the development time line can be shortened and adoption of closed injection wet-out and PU resin systems may be accelerated in the pultrusion industry. All information contained herein is provided "as is" without any warranties, express or implied, and under no circumstances shall the authors or Huntsman be liable for any damages of any nature whatsoever resulting from the use or reliance upon such information. Nothing contain in this publication should be construed as a license under any intellectual property right of any entity, or as a suggestion, recommendation, or authorization to take any action that would infringe any patent. The term "Huntsman" is used herein for convenience only, and refers to Huntsman Corporation, its direct and indirect affiliates, and their employees, officers, and directors. REFERENCES 1. Connolly, M., King, J.P., Shidaker, T.A., Duncan, A.C., Pultruding Polyurethane Composite Profiles: Practical Guidelines for Injection Box Design, Component Metering Equipment and Processing, Proceedings of Composites 2005, American Composites Manufacturers Association, Sept. 2005. 2. Connolly, M., King, J.P., Shidaker, T.A., Duncan, A.C., Processing and Characterization of Pultruded Polyurethane Composites, Proceedings of the 8 th World Pultrusion Conference, European Pultruders Technical Association, March 2006. 3. Connolly, M., King, J.P., Shidaker, T.A., Duncan, A.C., Characterization of Pultruded Polyurethane Composites: Environmental Exposure and Component Assembly Testing, Proceedings of Composites 2006, American Composites Manufacturers Association, Oct. 2006. 4. Jeswani, A.L., Roux, J.A., Vaughan, J.G., Impact of Axial Location of the Injection Slot for High Pull Speed Resin Injection Pultrusion, Proceedings of the 1 st Global Pultrusion Conference, Baltimore, MD, June 2006. 5. Gebart, B.R., Permeability of Unidirectional Reinforcements for RTM, Journal of Composite Materials, 26: 1100-1133 (1992).
Page 1 and 2: CFD Modeling of the Closed Injectio
Page 3: The momentum sources, S, defining t
Page 7 and 8: Figure 3: Porosity variation of the
Page 9: Figure 7: Influence of viscosity, g

CFD Modeling of the Closed Injection Wet-Out Process For Pultrusion

Create successful ePaper yourself

Delete template?

Save as template?