An Experimental Assessment of the Saturated Transverse Permeability of Non-crimped New Concept (NC2) Multiaxial Fabrics

Abstract

Over the past few years were developed some manufacturing processes involving resin impregnation in dry preforms prior to cure, and more specifically resin infusion across the fabric thickness in the so-called Resin Infusion Processes. Therefore, in these growingly used processes the transverse permeability of the fabrics will control both manufacturing cycles and dimensions, and consequently the mechanical properties of the final composites. A big effort has been realized to obtain reliable experimental techniques for measuring the transverse permeability. Since the differentiation between saturated and effective permeabilities is still discussed, and the flow front is hardly defined in such small dimensions (order of 1 mm), our measurements on some so-called Non-Crimped New Concept (N C2) are carried out for saturated flow, i.e. the fiber network is completely impregnated from the onset of the experiment. In our case [1], these measures rely on the measurements of the pressure drop induced by the flow of a controlled fluid across the fabrics, easily converted into transverse permeability through the Darcy's law. One of the main results of these measurements is that the low N C2 transverse permeability depends on the face of the fabric receiving the fluid. This original behaviour may, in turn, be translated into manufacturing guidelines to achieve optimal processing configuration. An attempt to relate this differential to the stitching hole surface is proposed which turns to explain minor phenomena. On the contrary, the 3D shape of the stitching hole reconstruction from polishings could yield some proper explanations.

Temperature Dependence of Resin Flow in a Resin Film Infusion (RFI) Process by Ultrasound Imaging

“…No measurable pressure drop was observed over the short flow distances in this work, indicating that the pressure was constant. Therefore, the pressure gradients were approximated as ΔP/z and ΔP/x [15,17,18]. Values of z and x of the fiber tows were determined previously as 0.55 mm and 1.05 mm, and ΔP was 100 kPa [15].…”

Macroscale Simulation of Fiber Bed Impregnation Utilizing Microscale Material Properties

“…Small preferential flow channels easily skewed outcomes of individual trials and caused front displacements to be larger than predicted. Elbouazzaoui et al [20] also proposed that handling of fabrics in their permeability tests may have been the largest source of experimental scatter. This problem is amplified with loose fibers used in this work.…”

Permeability of non-crimp fabric preforms

“…8.8 ), provide a more signifi cant contribution to the understanding and interpretation of permeability measurements of NCF. The measurements as carried out by Drapier et al (2002) and Elbouazzaoui et al (2005) can be used to identify the effect of the stitching as they varied the stitch density over a conveniently wide range. A similar approach was followed in the FALCOM project (Thuis, 2003), where a number of variants of the same NCF were analysed.…”