Numerical and experimental investigation of saturated transverse permeability of 2D woven glass fabrics based on material twins

Abstract

The transverse permeability of fibrous reinforcement is one of the critical parameters that govern fabrication efficiency and production quality in several liquid composite molding process variants devised to achieve transverse impregnation of fibrous reinforcements. It is difficult to precisely measure and predict the transverse permeability, because it is simultaneously affected by diverse factors, for example, the geometric features of the test mold, nesting between fabric layers, and flow‐induced compaction of the fiber bed. In this article, the saturated transverse permeability of 2D woven glass fabrics is investigated using information provided by mesostructural geometric models reproducing the real textile architecture. These models are created by micro‐CT aided geometric modeling, a recently proposed technique to analyze three‐dimensional images obtained by X‐ray microtomography. They are called “material twins” because they reproduce with assessed accuracy the geometrical configuration of the textile preform, are representative of material variability, and allow performing numerical simulations of flow or mechanical properties. Computer simulations of steady state transverse flows in material twins were carried out to evaluate the transverse permeability and compared to experiments. Issues concerning material variability due to nesting and the accuracy of transverse permeability measurements were considered and discussed. A good agreement was obtained between numerical and experimental values of transverse permeability. Both approaches show a significant influence of the number of layers considered, which can be explained by nesting between adjacent plies. Numerical simulations also illustrate how nesting significantly affects material variability.

On the design of test molds based on unidirectional saturated flows to measure transverse permeability in liquid composite molding

“…Note that saturated flow simulations are also carried out in Section 4.6 to show that the fill coefficient is also suitable to evaluate saturated flow patterns. It is important because the most common methods to measure K z are based on one-dimensional saturated flows, [13] although unsaturated tests have also been conducted by several investigators. [4,37,38] 4.2 | Geometrical models…”

“…It is possible to use a FDL between the preform and the perforated plates to facilitate the spread of the liquid flow on the preform surface. [ 10,13 ]…”

“…Note that a new problem may be introduced by the FDL because of possible nesting between the fabric and the FDLs. Huang et al [ 13 ] developed an iterative algorithm to estimate the nesting depth between FDLs and fabric, from 3D images sequence generated by micro‐CT scans. This approach was adopted in the present study to account for the nesting depth between FDLs and fabric when calculating the height H of the specimen as below: Using H in Equation ()) and Equation ()) allows correcting the fiber volume fraction and the corresponding transverse permeability.…”

“…Transverse permeability test devices based on onedimensional Darcy's law are usually made out of transparent plastic, [8] aluminum [8,9] or stainless steel. [13,25,26] The shape of the mold cavity cross-section can be constantly square or circular. Its size ranges from 79 to 150 mm.…”

Multiscale Model of the RTM Process: From Mesoscale Anisotropic Permeability of Woven Structures to Macroscale Resin Impregnation

“…However, the entire preform structure can be regarded as a combination of periodic woven structures, as shown in Figure a. The smallest RVE can be identified from the actual structure to simulate the resin flow. The way to select the corresponding RVE and the digitized models for 3D and 2.5D woven structures of the preforms are shown in Figure .…”