Modeling the Effect of Fiber Diameter and Fiber Bundle Count on Tow Impregnation during Liquid Molding Processes

Abstract

This paper explores the effect of fiber diameter and fiber bundle count on tow impregnation during liquid molding processes. Resin and fiber wetting properties play an important role on the resin infiltration behavior within a single fiber tow. Dynamic and equilibrium microflow models, based on Darcy's Law and force equilibrium at the resin flow front, assume that the infiltration of the resin is driven through capillary pressure and hindered by the entrapped gas within the tow. The results of the dynamic model show that the fiber tow count and the fiber diameter have a significant effect on the tow infiltration time. The infiltration time is 10 times longer for a 60 K carbon fiber tow than for a 6 K one. The infiltration time is also inversely proportional to the fiber diameter. As the fiber diameter is decreased 100 times, from 3.5 mm to 35 nm, the infiltration time increases 100 times for the same diameter tow. It also shows that fiber volume fraction also has a significant effect on the tow infiltration time and any fiber volume variations along the fiber tow could lead to dry spots in the composite due to the large differences in infiltration rates. The model indicates that the entrapment of a critical amount of air within a tow will lead to higher than acceptable void contents.

The threshold pressure of infiltration into fibrous preforms normal to the fibers’ axes

“…Powell [34] (see also [41,42]). The capillary pressure was described as function of the directional body angle (gradually changing while the liquid infiltrates between the fibers in a normal direction to their axes).…”

Experimental assessment of dual-scale resin flow-deformation in composites processing

“…(15), which present the deformation dependent anisotropic model, we note that, on one hand, the microscopic permeability K mic ¼ 1:7 Â 10 À13 m 2 , calculated by Gebart equation, considered to be constant. On the other hand, the channel permeability dependent on the compaction of the preform is plotted against time in Fig.…”

“…Permeability models, Eqs. (14) and (15) are an idealization of the true material. Still these models are easy to adapt for deformable material, and are based on sound physical grounds, thus the parameters have clear physical meaning.…”

“…There are number of previous research on tow impregnation phenomena, mostly in the context of liquid composite molding (LCM) or of composites based on commingled yarns [11][12][13][14][15][16][17]. In such processes, flow commonly occurs under isothermal conditions and relatively high driving pressures.…”

Spontaneous radial capillary impregnation across a bank of aligned micro-cylinders. Part II: Experimental investigations

“…The particular case of capillary flow across a bank of aligned micro-cylinders was approached via analytical (e.g. Bernet et al, 1999;Foley and Gillespie, 2005;Pillai and Advani, 1995;Potter, 1997), numerical (Bayramli and Powell, 1990;Dimitrovova and Advani, 2002;Pillai and Advani, 1995;Young, 2004) and experimental techniques (Batch et al, 1996;Chwastiak, 1971;Foley andGillespie, 2005, Pillai andAdvani, 1996).…”