Dynamic capillary impact on longitudinal micro-flow in vacuum assisted impregnation and the unsaturated permeability of inner fiber tows

Li, Min; Wang, Shaokai; Gu, Yi; Zhang, Zuoguang; Li, Yanxia; Potter, Kevin D

doi:10.1016/j.compscitech.2010.06.004

Cited by 32 publications

(19 citation statements)

References 29 publications

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“…The high resolution SXCT images showed an obtuse contact angles between the fluid and the fibers at the flow front. This behavior, which was opposed to the wetting contact angles measured in air, was also reported by other authors (Li et al, 2010;Verrey et al, 2006) and it cannot attributed to dynamic effects because the tomograms were acquired when the flow front was stopped. More likely, it seems to be a surface effect triggered in vacuum by the interaction between the fluid and the fiber sizing.…”

Section: Discussionsupporting

confidence: 64%

“…Similar discrepancies during vacuum infusion have been reported by other authors. For instance, Li et al (2010) studied the behavior of capillary forces during longitudinal impregnation of fiber tows subjected to external and vacuum-driven pressure gradients with several infiltration fluids. They found that the capillary pressure acted as a drag force for the infiltration under vacuum-assisted conditions for several fluids but this effect was not found if the stress gradient for infiltration was produced with compressed air.…”

Section: Local Fluid Flow Mechanismsmentioning

confidence: 99%

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An in situ investigation of microscopic infusion and void transport during vacuum-assisted infiltration by means of X-ray computed tomography

Vilà

Sket

Wilde

et al. 2015

Composites Science and Technology

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In situ vacuum-assisted infiltration experiments were carried out using synchrotron X-ray computed tomography (SXCT) to study the mechanisms of microfluid flow within a fiber tow. A single tow of E glass fibers was infused with a water and syrup blend using an apparatus designed and built for this purpose. The high resolution of the SXCT images allows the detailed reconstruction of individual fibers within the tow while the contrast between the different phases (air, fluid and fibers) was enough to track the fluid front position and shape as well as the void transport during infiltration. The ability of this technique to provide detailed information of microfluid flow and void transport in composite materials is clearly established. The fluid propagation at the microscopic level as well as the mechanisms of void transport within the tow were related to the wetting between the fluid and the fibers, the rheological properties of the fluid and the local microstructural details (fiber

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Section: Discussionsupporting

confidence: 64%

Section: Local Fluid Flow Mechanismsmentioning

confidence: 99%

An in situ investigation of microscopic infusion and void transport during vacuum-assisted infiltration by means of X-ray computed tomography

Vilà

Sket

Wilde

et al. 2015

Composites Science and Technology

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“…10 also shows that the individual voids are relatively small in the ±45° layers, whereas the larger voids are almost exclusively found in the 90° layer (Fig. 8) and can span dozens of fibres with a characteristic dimension greater than the fibre tow thickness [23,43,44]. Micrographs have shown the tendency for crack initiation and propagation from larger voids [9], which has been confirmed by a previous study on a different material using CT [10].…”

Section: Page 13supporting

confidence: 70%

High-resolution computed tomography in resin infused woven carbon fibre composites with voids

Sisodia

Garcea

George

et al. 2016

Composites Science and Technology

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Significance of paperRecent efforts in the composites industry towards less-expensive means to produce high-performance parts have often involved optimisation of liquid composite moulding processes such as resin transfer moulding (RTM). The most significant gap in part quality between RTM manufactured parts and traditional autoclave processes is the usually higher void content in the former, arising from the entrapment of bubbles during infusion, and the lower consolidation pressures used during such processes. Many laboratories around the world are working on understanding bubble entrapment and subsequent bubble mobility, so as to optimise RTM processes to reduce the concentration and size of voids. This paper contributes to that understanding with threedimensional examination using CT imaging of the morphology, size, clustering and location of the individual voids in composite parts made with RTM. Most important / novel contributionsThis paper presents visualisation of the voids in a composite part with significantly more statistical information regarding size distribution, orientation and location than has been previously shown in the literature. It also addresses a reinforcement architecture more typical to RTM, an un-balanced weave, than the unidirectional fabrics usually studied in previous work on void formation. Analysing a complex reinforcement along with the enhanced visualisation abilities of the CT-imaging technique allowed novel observations and conclusions regarding voids: 1) As the orientation angle between a reinforcement layer and the resin flow direction increases from parallel to perpendicular, larger voids and a greater number of voids were observed in that layer. This was linked to the resulting greater propensity for fatigue crack propagation between voids in layers transverse to the loading direction. A simple optimisation strategy is thus to infuse in a direction transverse to the expected primary load direction, thus creating the fewest voids in the transverse-to-load direction. 2) Voids accumulate around both the layer interfaces and yarns and are nearly completely absent from the layer thickness between those interfaces and away from yarns. 3) Void distribution follows the orientation of fibres in adjacent layers, suggesting that out-of-plane flow is a significant mechanism in void formation and mobility. 4) Observations 1-3 above all imply that current void formation and mobility models must be expanded from a microscale approach to the laminate scale, in order to focus on out-of-plane bubble movement and yarn bubble entrapment. M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT AbstractTomographic imaging using both microfocus radiation and synchrotron radiation was performed to assess the void defects in resin transfer moulded woven carbon fibre composites. The focus of this study is on characterising the void homology (e.g. local void size and spatial distribution) in relation to weave orientation, infusion direction and potential effects on damage formation in tensile loadin...

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“…The applied fluid pressure will dominate the liquid flow into the reinforcement, whereas capillary forces may have a strong drag or promotive effect acting on the velocity of penetrating flow. 6,7 However, the majority of fluid transport in the reinforcements, e.g. flow behind the flow front, is pressure driven only.…”

Section: Introductionmentioning

confidence: 99%

Influence of the micro-structure on saturated transverse flow in fibre arrays

Gommer

Endruweit

Long

2018

Journal of Composite Materials

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This study analyses the influence of the random filament arrangement in fibre bundles on the resin flow behaviour. Transverse steady-state resin flow that occurs behind a liquid resin flow front was simulated numerically through statistically equivalent micro-structures at high-fibre volume fractions, V f > 0.6, as observed in fibre bundles. The need of applying a minimum gap distance between neighbouring filaments was overcome by automated local mesh refinement. The derived permeability values showed significant scatter. Convergence of these values was determined at a ratio of flow length to filament radius greater than 20 for all three analysed fibre volume fractions. Mean permeabilities were between 6 and 10 times lower than those predicted for a hexagonal fibre array. A statistical model is proposed, which is able to predict the scatter of observed permeabilities based on simple micro-structural descriptors.

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Dynamic capillary impact on longitudinal micro-flow in vacuum assisted impregnation and the unsaturated permeability of inner fiber tows

Cited by 32 publications

References 29 publications

An in situ investigation of microscopic infusion and void transport during vacuum-assisted infiltration by means of X-ray computed tomography

An in situ investigation of microscopic infusion and void transport during vacuum-assisted infiltration by means of X-ray computed tomography

High-resolution computed tomography in resin infused woven carbon fibre composites with voids

Influence of the micro-structure on saturated transverse flow in fibre arrays

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