Center for Composite Materials - University of Delaware

Research Summary

Multiscale Flow Modeling to Predict Tow Impregnation

Authors: Michael Yeager, Pavel Simacek, Suresh G. Advani

Introduction

• The main objective of this research is to optimize the performance of composite materials in extreme dynamic environments
• Voids, which can influence energy absorption, are caused by the entrapment of air and gasses during composite processing
-Due to dual scale of the fiber preform permeability, the resin will flow around the fibers and then into fiber tows – voids will exist inside of and between tows

Multiscale Resin Flow Modeling

• Key flow parameters will be using microscopic unit cells and will be applied to three dimensional mesocopic process models of fiber tow filling from a finite volume of resin

• Mesoscopic model can be used to predict the distribution of resin within tows for selected initial conditions, shown schematically below

Microscale Capillary Pressure

• A microscopic model to predict capillary forces for resin moving through unit cells containing fibers, including the influence of neighboring fibers
• Capillary pressure predictive tools developed (numerical and analytical models):

• Comparing the average capillary pressure from the methods, and showing effect of moving the center fiber in the x and y directions

Mesoscale Tow Infusion

• Methodology for including microscopic capillary pressure in meso scale fiber tow impregnation models

Tow Infusion: Results for Gaussian Fiber Distribution

• Previous tow filling models have assumed a constant fiber volume fraction throughout the tow, leading to a single large void in the center
• Fiber tows commonly have a Gaussian fiber volume fraction distribution
• The shape of the resin flow front is greatly influenced by including a Gaussian fiber volume fraction distribution for the tow’s elements, shown below:

• The number and size of voids are also greatly influenced when realistic fiber volume fraction distributions are introduced to the model (voids circled)

Tow Infusion: Influence of Time Under Vacuum

• Leaving a part under vacuum for a longer period of time will allow more air to be removed from the tow, resulting in a lower initial pressure inside of the tow
- This will lead to slower production rates and increased production costs
• Air pressure in tow computed with the ideal gas law
• Utilized model from Cender et al. to model air removed as a function of time*
• Leaving the part under vacuum for a longer period of time has diminished returns

Related Publications

Journal Papers
• Yeager, M., W. R. Hwang, and S. G. Advani, “Prediction of Capillary Pressure for Resin Flow Between Fibers” Composites Science and Technology 126 (2016):130-38.
• Yeager, Michael, and Suresh G. Advani. "Numerical Model of Fiber Wetting with Finite Resin Volume." Integrating Materials Integrating Materials and Manufacturing Innovation 4.1 (2015).

Conference Proceedings and Presentations
• Yeager, M., P. Simacek, S. G. Advani, “A Model for Void Formation and Movement Through Fiber Tows,” The Composites and Advanced Materials Expo (CAMX), Dallas, TX, October 26-29, 2015.
• Yeager, M., W. R. Hwang, and S. G. Advani, “Prediction of Capillary Pressure for Resin Flow within Fiber Unit Cells,” American Society for Composites 30th Technical Conference, East Lansing, MI, September 28-30, 2015.
• Yeager, M., P. Simacek, S. G. Advani, “Multiscale Flow Modeling and Simulation to Predict Void Formation and Transport in Composite Manufacturing,” 10th International Workshop on Structural Health Monitoring, Stanford, CA, September 1-3, 2015.
• Yeager, M., and S. G. Advani, "Resin Flow into Fiber Tows: Role of Fiber Microstructure," SAMPE 2015, Baltimore, MD, May 18-21, 2015.
• Yeager, M., R. Ganesh, S. Yarlagadda, S.G. Advani, J. W. Gillespie Jr. “A Unit Cell Model to Predict Impact of Geometric and Processing Parameters on Energy Absorbed by Fiber Composites.” Mach Conference 2015, Annapolis, MD, April 8-10, 2015.
• Yeager, M., and S. G. Advani, "Parametric Study of Fiber Tow Wetting by Finite Volume of Resin," SAMPE 2014, Seattle, WA, June 2-5, 2014.
• Yeager, M., S. G. Advani, S. Yarlagadda. "Dynamics of Wetting on Fiber Surfaces by a Finite Volume of Resin." Mach Conference 2014, Annapolis, MD, April 9-11, 2014.

Acknowledgements

Research was sponsored by the Army Research Laboratory and was accomplished under Cooperative Agreement Number W911NF-12-2-0022. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the Army Research Laboratory or the U.S. Government. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation herein. 

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