OJINM  Vol.2 No.3 , July 2012
Experimental Characterization by Fluorescence of Capillary Flows in the Fiber Tows of Engineering Fabrics
ABSTRACT
Liquid Composite Molding (LCM) is an increasingly used class of processes to manufacture high performance composites. In LCM, the fibrous reinforcement is first laid in a mold cavity. After closure of the mold or covering of reinforcement with a plastic bag, a polymer resin is either injected or infused under vacuum through the fiber bed. The engineering fabrics commonly used in LCM possess generally dual scale architecture in terms of porosity: microscopic pores exist between the filaments in the fiber tows, while macroscopic pores appear between the tows as a result of the stitching/weaving fabrication process. On a microscopic scale, capillary flows in fiber tows play a major role on the quality of composites made by resin injection through fibrous reinforcements. In order to better understand the mechanisms that govern the impregnation of fibrous reinforcements in LCM, a study of wicking behavior is carried out in fiber tows. The experimental approach is based on capillary rise experiments, which are less expensive and time-consuming than other more standard characterization techniques often used in porous media. In addition, it allows gathering representative data on the wicking properties of fiber tows as a function of their morphological characteristics such as micro-porosity, total cross-section area, specific surface area, filament diameter and packing configuration. The morphological properties of the fiber tows will also be characterized by other standard experimental methods in order to compare with the results obtained by capillary rise experiments. These standard methods include gravimetry for the micro-porosity and fiber mass density, microscopic analysis to measure the filament diameter, cross-section area and packing configuration of the filaments and capillary flow porometry to evaluate the equivalent pore diameter. The capillary rise method has already been used not only in Soil Mechanics, but also to characterize engineering textiles used in high performance composites. Such experiments are not easy to perform, because of technical difficulties such as textile geometrical alteration during testing, changes in fluid properties due to solvent evaporation and inaccurate observation of the progression of the capillary front (fading). To circumvent these problems, a monitoring technique based on fluorescent dye penetration inspection (DPI) and CCD image acquisition is proposed in this investigation. Visual monitoring of the capillary front is coupled with real-time fluid mass acquisition using a high resolution balance. Experimental observations on the height of the capillary front and the fluid mass absorbed by the fiber tows can be analyzed by four imbibition models. These models consider the evolution of the capillary height with (model I) or without gravity (model II) and of the fluid mass absorbed by capillary effect with (model III) or without gravity (model IV). The models without gravity will be used on short imbibition distances to derive the microscopic properties of fiber tows from the experimentally observed evolutions of the capillary height and the fluid mass absorbed by capillarity. After describing the new capillary rise setup devised for the fiber tow experiments, a set of experiments is carried out to characterize the properties of the fiber tows and investigate the wicking phenomena along the warp and weft directions. The consistency of this approach is compared with more standard methods. At the same time, the impact of fiber sizing on the tow wicking behavior is investigated. Note that experimental evaluations of tow permeability can also be derived from this approach. The results compare well with permeability predictions based on Blake-Kozeny-Carman models. In the future, it will be possible to apply the same experimental approach to engineering fabrics. Indeed, a comprehensive wicking characterization of fibrous reinforcements is expected to provide useful information in order to evaluate the optimal processing conditions of high performance composites fabricated by Liquid Composite Molding.

Cite this paper
F. LeBel, A. Fanaei, É. Ruiz and F. Trochu, "Experimental Characterization by Fluorescence of Capillary Flows in the Fiber Tows of Engineering Fabrics," Open Journal of Inorganic Non-metallic Materials, Vol. 2 No. 3, 2012, pp. 25-45. doi: 10.4236/ojinm.2012.23004.
References
[1]   F. Trochu, et al., “Advanced Numerical Simulation of Liquid Composite Molding for Process Analysis and Optimization,” Composites Part A: Applied Science and Manufacturing, Vol. 37, No. 6, 2006, pp. 890-902. doi:10.1016/j.compositesa.2005.06.003

[2]   J. García, et al., “An Efficient Solver of the Saturation Equation in Liquid Composite Molding Processes,” International Journal of Material Forming, Vol. 3, Supp. 2, 2010, pp. 1295-1302. doi:10.1007/s12289-010-0681-8

[3]   J. Leclerc, “Amélioration du Procédé RTM par L’Optimisation des Paramètres D’Injection,” Master Thesis, Ecole Polytechnique, Montreal, 2008.

[4]   J. S. Leclerc and E. Ruiz, “Porosity Reduction Using Optimized Flow Velocity in Resin Transfer Molding,” Composites Part A: Applied Science and Manufacturing, Vol. 39, No. 12, 2008, pp. 1859-1868. doi:10.1016/j.compositesa.2008.09.008

[5]   S. R. Ghiorse, “Effect of Void Content on the MechanicalProperties of Carbon Epoxy Laminates,” SAMPE Quarterly, Vol. 24, No. 2, 1993, pp. 54-59.

[6]   N. C. W. Judd and W. W. Wright, “Voids and Their Effects on the Mechanical Properties of Composites—An Appraisal,” SAMPE Journal, Vol. 14, No. 1, 1978, pp. 10-14.

[7]   J. Lambert, et al., “3D Damage Characterisation and the Role of Voids in the Fatigue of Wind Turbine Blade Materials,” Composites Science and Technology, Vol. 72, No. 2, 2012, pp. 337-343. doi:10.1016/j.compscitech.2011.11.023

[8]   M. Haider, P. Hubert and L. Lessard, “An Experimental Investigation of Class a Surface Finish of Composites Made by the Resin Transfer Molding Process,” Composites Science and Technology, Vol. 67, No. 15-16, 2007, pp. 3176-3186. doi:10.1016/j.compscitech.2007.04.010

[9]   E. Ruiz, et al., “Optimization of Injection Flow Rate to Minimize Micro/Macro-Voids Formation in Resin Transfer Molded Composites,” Composites Science and Technology, Vol. 66, No. 3-4, 2006,, pp. 475-486. doi:10.1016/j.compscitech.2005.06.013

[10]   V. Achim and E. Ruiz, “Guiding Selection for Reduced Process Development Time in RTM,” International Journal of Material Forming, Vol. 24, 2010, pp. 1277-1286. doi:10.1007/s12289-009-0630-6

[11]   G. L. Batch, Y. T. Chen and C. W. Macosko, “Capillary Impregnation of Aligned Fibrous Beds: Experiments and Model,” Journal of Reinforced Plastics and Composites, Vol. 15, No. 10, 1996, pp. 1027-1050. doi:10.1177/073168449601501004

[12]   S. C. Amico and C. Lekakou, “Axial Impregnation of a Fiber Bundle. Part 1: Capillary Experiments,” Polymer Composites, Vol. 23, No. 2, 2002, pp. 249-263. doi:10.1002/pc.10429

[13]   J.-M. Sénécot, “étude de L’Imprégnation Capillaire de Tissus de Verre,” Ph.D. Thesis, Université de Haute Alsace, Montréal, 2002.

[14]   S. C. Amico and C. Lekakou, “Axial Impregnation of a Fiber Bundle. Part 2: Theoretical Analysis,” Polymer Composites, Vol. 23, No. 2, 2002, pp. 264-273. doi:10.1002/pc.10430

[15]   Y.-L. Hsieh and B. Yu, “Liquid Wetting, Transport, and Retention Properties of Fibrous Assemblies Part I: Water Wetting Properties of Woven Fabrics and Their Constituent Single Fibers,” Textile Research Journal, Vol. 62, No. 11, 1992, pp. 677-685.

[16]   E. Bayramli and R. L. Powell, “Experimental Investigation of the Axial Impregnation of Oriented Fiber-Bundles by Capillary Forces,” Colloids and Surfaces, Vol. 56, 1991, pp. 83-100. doi:10.1016/0166-6622(91)80115-5

[17]   S. C. Amico, “Permeability and Capillary Pressure in the Infiltration of Fibrous Porous Media in Resin Transfer Moulding,” Ph.D. Thesis, University of Surrey, Guildford, 2000.

[18]   S. Chwastiak, “Wetting of Carbon Yarns from Wicking Rate Measurements,” Journal of Colloid and Interface Science, Vol. 31, No. 1, 1971, pp. 437-442. doi:10.1016/0021-9797(73)90293-2

[19]   K. E. Scher, “Comparison of Wicking and Single Filament Techniques for Determining Contact Angles,” Master Thesis, University of Washington, Washington CD, 1983.

[20]   K. M. Pillai and S. G. Advani, “Wicking across a FiberBank,” Journal of Colloid and Interface Science, Vol. 183, No. 1, 1996, pp. 100-110. doi:10.1006/jcis.1996.0522

[21]   J. G. Williams, C. E. M. Morris and B. C. Ennis, “Liquid Flow through Aligned Fiber Beds,” Polymer Engineering and Science, Vol. 14, No. 6, 1974, pp. 413-419. doi:10.1002/pen.760140603

[22]   M. Hamdaoui, F. Fayala and S. B. Nasrallah, “Dynamics of Capillary Rise in Yarns: Influence of Fiber and Liquid Characteristics,” Journal of Applied Polymer Science, Vol. 104, 2007, pp. 3050-3056.

[23]   Y. K. Kamath, et al., “Wicking of Spin Finishes and Related Liquids into Continuous Filament Yarns,” Textile Research Journal, Vol. 64, No. 1, 1994, pp. 33-40. doi:10.1177/004051759406400104

[24]   N. R. S. Hollies, M .M. Kaessinger and H. Bogaty, “Water Transport Mechanisms in Textile Materials1 Part I: The Role of Yarn Roughness in Capillary-Type Penetration,” Textile Research Journal, Vol. 26, No. 11, 1956, pp. 829-835. doi:10.1177/004051755602601102

[25]   A. W. Adamson and A. P. Gast, “Physical Chemistry of Surfaces,” 6th edition, 1997, Wiley, New York.

[26]   R. W. Johnson, “The Handbook of Fluid Dynamics,” CRC Press, Boca Raton, 1998.

[27]   K. J. Ahn, J. C. Seferis and J. C. Berg, “Simultaneous Measurements of Permeability and Capillary-Pressure of Thermosetting Matrices in Woven Fabric Reinforcements,” Polymer Composites, Vol. 12, No. 3, 1991, pp. 146-152. doi:10.1002/pc.750120303

[28]   N. R. S. Hollies, et al., “Water Transport Mechanisms in Textile Materials: Part II: Capillary-Type Penetration in Yarns and Fabrics,” Textile Research Journal, Vol. 27, No. 1, 1957, pp. 8-13. doi:10.1177/004051755702700102

[29]   J. Bear, “Dynamics of Fluids in Porous Media,” American Elsevier, New York, 1972.

[30]   S. Brunauer, P. H. Emmett and E. Teller, “Adsorption of gases in multimolecular layers,” Journal of the American Chemical Society, Vol. 60, No. 2, 1938, pp. 309-319. doi:10.1021/ja01269a023

[31]   A. Siebold, et al., “Effect of Dynamic Contact Angle on Capillary Rise Phenomena,” Colloids and Surfaces A, Vol. 161, No. 1, 2000, pp. 81-87. doi:10.1016/S0927-7757(99)00327-1

[32]   Washburn, E.W., “The Dynamics of Capillary Flow,” Physical Review, Vol. 18, No. 3, 1921, pp. 273-283. doi:10.1103/PhysRev.17.273

[33]   J. Bico and D. Quere, “Precursors of Impregnation,” Europhysics Letters, Vol. 61, No. 3, 2003, pp. 348-353. doi:10.1209/epl/i2003-00196-9

[34]   B. R. Gebart, “Permeability of Unidirectional Reinforcements for RTM,” Journal of Composite Materials, Vol. 26, No. 8, 1992, pp. 1100-1133. doi:10.1177/002199839202600802

[35]   H. Yanazawa, K. Ohshika and T. Matsuzawa, “Precision Evaluation in Kr Adsorption for Small BET Surface Area Measurements of Less than 1 m2,” Adsorption, Vol. 6, 2000, pp. 73-77.

[36]   M. J. Weber, “Handbook of Optical Materials,” CRC Press, Boca Raton, 2003.

[37]   J. L. Thomason and L. J. Adzima, “Sizing Up the Interphase: An Insider’s Guide to the Science of Sizing,” Composites Part A: Applied Science and Manufacturing, Vol. 32, No. 3-4, 2001, pp. 313-321. doi:10.1016/S1359-835X(00)00124-X

[38]   S. H. Saidpour, “The Effect of Fibre/Matrix Interfacial Interactions on the Mechanical Properties of Unidirectional E-Glass Reinforced Vinyl Ester Composites,” Ph.D. Thesis, Loughborough University of Technology, Leicestershire, 1991.

[39]   N. Otsu, “Threshold Selection Method from Gray-Level Histograms,” IEEE Transactions on Systems, Man and Cybernetics, Vol. 9, No. 1, 1979, pp. 62-66.

[40]   V. Wolff, et al., “Determination of Surface Heterogeneity by Contact Angle Measurements on Glassfibres Coated with Different Sizings,” Journal of Materials Science, Vol. 34, No. 15, 1999, pp. 3821-3829. doi:10.1023/a:100460491722

 
 
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