The effect of vacuum assistance in resin transfer moulding

Hayward, Joel; Harris, B.

doi:10.1016/0956-7143(90)90163-q

Cited by 49 publications

(24 citation statements)

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“…h V,T and h V,C in Equations (5) and (6). These parameters are not necessary, however, to predict the optimal modified capillary number which can be obtained by Equations (7) and (8). This implies that the process condition can be optimized to minimize the void formation without experimental measurement of void content, once the preform microstructure properties and the liquid properties are known.…”

Section: Resultsmentioning

confidence: 97%

“…[1][2][3][4][5][6] Air entrapment by non-uniform resin flow at the flow front is regarded as the main source of void generation in the resin transfer molding process whereas other phenomena such as volatile generation and premature resin gelation during the curing process also induce the void formation. [7][8][9][10][11] In general, the heterogeneous microstructure of fiber preform is considered to be the main reason for the non-uniform resin flow at the flow front. [11] Frequently, high count tow fabrics are used as fiber preform to enhance the mechanical properties.…”

Section: Introductionmentioning

confidence: 99%

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Analytical modeling andin situmeasurement of void formation in liquid composite molding processes

Guéroult

Lebel-Lavacry

Park

et al. 2013

Advanced Composite Materials

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Liquid composite molding processes are widely accepted in the aeronautic industry to manufacture large and complex structural parts. In spite of their cost-effectiveness, void defects created during the manufacturing process are a major issue of these processing techniques because they have detrimental effects on the mechanical performance. The reliable modeling is still a difficult task and experimental observations are usually adopted for the analysis of void formation mechanism, however, because many different physics are simultaneously involved during the mold filling process and the resin curing process. The complexity of the void formation physics implies the need for an in situ measurement of void formation not in the final part but in the mold filling procedure during the manufacturing process to better understand the void mechanism. In this regard, we present a sensor system measuring the electric conductivity for the in situ monitoring of void formation during the mold filling process. We also propose a theoretical model to predict void formation in a quantitative way with the properties of the resin and the fiber reinforcement. The model prediction is compared with the experimental data obtained by the sensor system to validate the model.

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Section: Resultsmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Analytical modeling andin situmeasurement of void formation in liquid composite molding processes

Guéroult

Lebel-Lavacry

Park

et al. 2013

Advanced Composite Materials

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“…Incomplete wetting or impregnation often results in the formation of voids or air entrapment. Although the occurrence of voids has been frequently documented and is recognized as a major problem in composites (Bascom and Romans, 1968;Kohn et al, 1968;Williams et al, 1974;Judd and Wright, 1978;Gonzalez, 1983;Behrens, 1983;Macosko, 1989;Kardos et al, 1986;Kamal et al, 1986;Gutowski et al, 1987;Molnar et al, 1989;Elmendorp and During, 1990;Hayward and Harris, 1990;Parnas and Phelan, 1991;McGeehan, 1991;Mahale et al, 1992;Lundstrom et al, 1992;Stabler et al, 19921, the exact mechanism of void formation is not clear due to its complexity. Generally, the void or air bubble formation can include mechanical entrapment as well as growth of bubbles existing in the resin phase.…”

Section: Introductionmentioning

confidence: 97%

Wetting of fiber mats for composites manufacturing: I. Visualization experiments

1995

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“…Very good results with vacuum assistance were reported by Hayward and Harris [1,2] who found that the void volume fraction (V,) was lowered considerably by the application of vacuum. This positive influence was present regardless of reinforcement type, resin type and resin viscosity.…”

Section: Introduction M Hementioning

confidence: 86%

Void Formation in RTM

Lundström

Gebart

Lundemo

1993

Journal of Reinforced Plastics and Composites

114

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The problem of void formation in composites processing is very important since the physical and mechanical properties as well as the finish of the product are strongly influenced by the presence of voids. Examples of properties that are adversely affected by voids are the strength and the weather resistance of the composite. The knowledge about void formation in the RTM process is still very limited compared to what is known about autoclave production of composites, and it is not clear whether the voids are created by diffusion growth, mechanical entrapment or some other mechanism.Our research has been concentrated on the influence of vacuum assistance on the void formation in RTM. The experiments were made in a flat mould with edge injection (unidirectional flow from one side to the other) in which the vacuum level could be varied from atmospheric pressure to about 1 kPa (10 mbar). The total flow length was 0.55 m in all experiments. The void volume fraction was determined with optical microscopy and image analysis and it was found that most of the voids were concentrated to a small area close to the flow front. The influence of vacuum was that the maximum void content and the size of the region with voids decreased with increasing vacuum assistance. The qualitative behavior can be explained with a simple theory based on the ideal gas law and the assumption that the voids are created by mechanical entrapment.

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The effect of vacuum assistance in resin transfer moulding

Cited by 49 publications

References 0 publications

Analytical modeling andin situmeasurement of void formation in liquid composite molding processes

Analytical modeling andin situmeasurement of void formation in liquid composite molding processes

Wetting of fiber mats for composites manufacturing: I. Visualization experiments

Void Formation in RTM

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