Guiding selection for reduced process development time in RTM

Achim, Vincent; Ruiz, Édu

doi:10.1007/s12289-009-0630-6

Cited by 25 publications

(35 citation statements)

References 32 publications

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“…The problem is rather complex, given the number of interconnected physical variables and the various possible tool configurations. However, it has become possible to optimize single process parameters, for example to find the best time-dependent injection flow rate [21] and to improve the selection of processing temperatures, so as to reduce cycle time and improve part quality [9].…”

Section: State Of the Artmentioning

confidence: 99%

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A Dimensionless Characteristic Number for Process Selection and Mold Design in Composites Manufacturing: Part I—Theory

et al. 2020

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The present article introduces a dimensionless number devised to assist composite engineers in the fabrication of continuous fiber composites by Liquid Composite Molding (LCM), i.e., by injecting a liquid polymer resin through a fibrous reinforcement contained in a closed mold. This dimensionless number is calculated by integrating the ratio of the injection pressure to the liquid viscosity over the cavity filling time. It is hereby called the “injectability number” and provides an evaluation of the difficulty to inject a liquid into a porous material for a given part geometry, permeability distribution, and position of the inlet gate. The theoretical aspects behind this new concept are analyzed in Part I of the article, which demonstrates the invariance of the injectability number with respect to process parameters like constant and varying injection pressure or flow rate. Part I also details how process engineers can use the injectability number to address challenges in composite fabrication, such as process selection, mold design, and parameter optimization. Thanks to the injectability number, the optimal position of the inlet gate can be assessed and injection parameters scaled to speed up mold design. Part II of the article completes the demonstration of the novel concept by applying it to a series of LCM process examples of increasing complexity.

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Section: State Of the Artmentioning

confidence: 99%

“…LCM processes enable the fabrication of large composite parts having high specific mechanical properties, at a significantly lower cost and with a shorter cycle time compared to several other manufacturing technologies [9,10]. Automating production is an important factor to reduce costs 1.…”

Section: Introductionmentioning

confidence: 99%

A Dimensionless Characteristic Number for Process Selection and Mold Design in Composites Manufacturing: Part I—Theory

et al. 2020

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“…Over the last decades, several experimental studies have been carried out on capillary flows in fiber tows based on the capillary rise method. In this regard, Batch et al, Bayramli and Powell, Chwastiak, Scher as well as Pillai and Advani have all characterized wicking in fiber tows by measuring the uptake fluid mass [11,16,[18][19][20]. Batch et al carried out a review on the uptake fluid mass monitoring technique to characterize the wicking behaveior of compacted powders, soils and other solid porous media [11].…”

Section: Bibliographymentioning

confidence: 99%

“…In the work of Pillai and Advani, glass fiber tows were encased between polycarbonate plates whereas, in the work of Batch et al, they were held in PTFE tubes, in order to characterize their transversal and axial wicking behavior by measuring the uptake fluid mass [11,20]. The infiltration fluids used for these capillary rise tests were several kinds of industrial fluids.…”

Section: Bibliographymentioning

confidence: 99%

Experimental Characterization by Fluorescence of Capillary Flows in the Fiber Tows of Engineering Fabrics

Lebel¹,

Fanaei²,

Ruiz³

et al. 2012

OJINM

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Liquid Composite Molding (LCM) is an increasingly used class of processes to manufacture high performance composites. In LCM, the fibrous reinforcement is first laid in a mold cavity. After closure of the mold or covering of reinforcement with a plastic bag, a polymer resin is either injected or infused under vacuum through the fiber bed. The engineering fabrics commonly used in LCM possess generally dual scale architecture in terms of porosity: microscopic pores exist between the filaments in the fiber tows, while macroscopic pores appear between the tows as a result of the stitching/weaving fabrication process. On a microscopic scale, capillary flows in fiber tows play a major role on the quality of composites made by resin injection through fibrous reinforcements. In order to better understand the mechanisms that govern the impregnation of fibrous reinforcements in LCM, a study of wicking behavior is carried out in fiber tows. The experimental approach is based on capillary rise experiments, which are less expensive and time-consuming than other more standard characterization techniques often used in porous media. In addition, it allows gathering representative data on the wicking properties of fiber tows as a function of their morphological characteristics such as micro-porosity, total cross-section area, specific surface area, filament diameter and packing configuration. The morphological properties of the fiber tows will also be characterized by other standard experimental methods in order to compare with the results obtained by capillary rise experiments. These standard methods include gravimetry for the micro-porosity and fiber mass density, microscopic analysis to measure the filament diameter, cross-section area and packing configuration of the filaments and capillary flow porometry to evaluate the equivalent pore diameter. The capillary rise method has already been used not only in Soil Mechanics, but also to characterize engineering textiles used in high performance composites. Such experiments are not easy to perform, because of technical difficulties such as textile geometrical alteration during testing, changes in fluid properties due to solvent evaporation and inaccurate observation of the progression of the capillary front (fading). To circumvent these problems, a monitoring technique based on fluorescent dye penetration inspection (DPI) and CCD image acquisition is proposed in this investigation. Visual monitoring of the capillary front is coupled with real-time fluid mass acquisition using a high resolution balance. Experimental observations on the height of the capillary front and the fluid mass absorbed by the fiber tows can be analyzed by four imbibition models. These models consider the evolution of the capillary height with (model I) or without gravity (model II) and of the fluid mass absorbed by capillary effect with (model III) or without gravity (model IV). The models without gravity will be used on short imbibition distances to derive the microscopic properties of fiber tows from the e...

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“…However, these methods come at a cost and are not always adapted to large components or parts of complex geometry. Because of the stringent requirements for high performance composites encountered especially in aerospace applications, the development of practical strategies to produce composites of high impregnation quality represents an important industrial goal [16]. As proposed by Trochu et al [4], control of the injected flow rate to ensure that the front velocity is close to the optimal conditions is an interesting approach to reach that goal.…”

Section: Introductionmentioning

confidence: 99%

Capillary Characterization of Fibrous Reinforcement and Optimization of Injection Strategy in Resin Transfer Molding

2018

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During composite manufacturing, minimizing the residual void content is a key issue to ensure optimal mechanical performance of final products. For injection processes such as Resin Transfer Molding (RTM), the impregnation velocity has a direct impact on void creation at the flow front by mechanical entrapment of air bubbles. Previous work proposed to study capillary imbibition in fibrous reinforcement to determine optimal filling conditions during practical manufacturing. The objective of this study is to investigate further this possibility. For that purpose, an improved experimental procedure is proposed to estimate the optimal impregnation velocity from capillary rise tests and understand its effect in parts of varying geometry. Capillary rise experiments were carried out with an enhanced experimental protocol, and a new post processing technique was evaluated to analyze the results. The position of the capillary flow front was then used to deduce the optimal impregnation velocity range based on the Lucas-Washburn flow model. A series of injections were also carried out with a laboratory scale RTM mold to study the influence of flow velocity on the residual void content. Results show that the prediction from capillary characterization is close to the optimal velocity value deduced from manufacturing experiments. The study also highlights the importance of void transport during processing and suggests that the injection strategy (i.e., flow rate history) and the mold configuration (i.e., divergent versus convergent flow) are important process parameters that may influence void content and cycle time.

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Guiding selection for reduced process development time in RTM

Cited by 25 publications

References 32 publications

A Dimensionless Characteristic Number for Process Selection and Mold Design in Composites Manufacturing: Part I—Theory

A Dimensionless Characteristic Number for Process Selection and Mold Design in Composites Manufacturing: Part I—Theory

Experimental Characterization by Fluorescence of Capillary Flows in the Fiber Tows of Engineering Fabrics

Capillary Characterization of Fibrous Reinforcement and Optimization of Injection Strategy in Resin Transfer Molding

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