Permeability properties of composite reinforcements

Michaud, Véronique

doi:10.1016/b978-0-12-819005-0.00014-9

Cited by 4 publications

(2 citation statements)

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“…( 6) is used to evaluate its value, often neglecting progressive saturation and any capillary effects at the flow front, assuming , where Pi is the inlet pressure, and Pf the pressure in the preform just ahead of the flow front (atmospheric pressure in general). Thus, this value, often named Kunsat to reflect the fact that it measured during flow (and that saturation is taking place during measurement), is computed as: (7) This value is distinguished from the saturated permeability, Ksat, measured from the flow rate Qout at the outlet, after the fluid has filled the whole length of preform Lf: (8) where A is the cross-section area of the fabric stack [27].…”

Section: In-plane Permeability Measurementmentioning

confidence: 99%

LCM of thermoset-based fiber reinforced composites for large-scale applications: are process kinetics and structural properties antagonistic?

Michaud

2023

IOP Conf. Ser.: Mater. Sci. Eng.

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This article reviews the main methods to manufacture large-scale composite parts, with a focus on Liquid Composite Molding techniques of thermoset-based fiber reinforced structural parts. As this process relies on the impregnation of a dry textile stack, this manufacturing step is crucial in terms of part production rate, and part quality. To increase the process kinetics, a large effort has been devoted to increase the permeability of the textile preforms, while keeping a similar fiber content. An increase of almost two orders of magnitude can be attained if the textile shows a strong separation of scales between densely packed tows and large intra-two spaces. This however leads to a potential degradation in the resulting structural properties, particularly in dynamic mode due to the presence of the resin rich pockets. Alternative solutions emerge, which may help reach a cost-effective compromise.

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Section: In-plane Permeability Measurementmentioning

confidence: 99%

LCM of thermoset-based fiber reinforced composites for large-scale applications: are process kinetics and structural properties antagonistic?

Michaud

2023

IOP Conf. Ser.: Mater. Sci. Eng.

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“…In most cases, the reinforcing fibers or filaments, which have a diameter in the order of 7-20 μm, are produced in the form of yarns, comprising several thousands of filaments, which are then combined by textile processes into mats, woven, knitted or braided fabrics, as well as non-crimp fabrics or polymer bound tapes. As a result, fiber textiles or preforms used in composite structures exhibit highly anisotropic, in general dual scale pore networks that span from micron scale pores between fibers to millimeter scale pores between fiber yarns (Michaud, 2021). Owing to the nature of the composite manufacturing processes, capillary action is usually coupled with hydrodynamics, since flow is driven by externally applied pressure, as well as with the (chemo)rheology of the polymer matrices; in addition, the matrix material in liquid form is generally much more viscous than water, up to several orders of magnitude, leading to a strong dependence of the mechanisms to the interface velocity.…”

Section: Introductionmentioning

confidence: 99%

Capillary Effects in Fiber Reinforced Polymer Composite Processing: A Review

et al. 2022

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Capillarity plays a crucial role in many natural and engineered systems, ranging from nutrient delivery in plants to functional textiles for wear comfort or thermal heat pipes for heat dissipation. Unlike nano- or microfluidic systems with well-defined pore network geometries and well-understood capillary flow, fiber textiles or preforms used in composite structures exhibit highly anisotropic pore networks that span from micron scale pores between fibers to millimeter scale pores between fiber yarns that are woven or stitched into a textile preform. Owing to the nature of the composite manufacturing processes, capillary action taking place in the complex network is usually coupled with hydrodynamics as well as the (chemo) rheology of the polymer matrices; these phenomena are known to play a crucial role in producing high quality composites. Despite its importance, the role of capillary effects in composite processing largely remained overlooked. Their magnitude is indeed rather low as compared to hydrodynamic effects, and it is difficult to characterize them due to a lack of adequate monitoring techniques to capture the time and spatial scale on which the capillary effects take place. There is a renewed interest in this topic, due to a combination of increasing demand for high performance composites and recent advances in experimental techniques as well as numerical modeling methods. The present review covers the developments in the identification, measurement and exploitation of capillary effects in composite manufacturing. A special focus is placed on Liquid Composite Molding processes, where a dry stack is impregnated with a low viscosity thermoset resin mainly via in-plane flow, thus exacerbating the capillary effects within the anisotropic pore network of the reinforcements. Experimental techniques to investigate the capillary effects and their evolution from post-mortem analyses to in-situ/rapid techniques compatible with both translucent and non-translucent reinforcements are reviewed. Approaches to control and enhance the capillary effects for improving composite quality are then introduced. This is complemented by a survey of numerical techniques to incorporate capillary effects in process simulation, material characterization and by the remaining challenges in the study of capillary effects in composite manufacturing.

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