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Resin infusion between double flexible tooling: prototype developmentJ.R. Thagard, O.I. Okoli*, Z. Liang, H.-P. Wang, C. ZhangDepartment of Industrial Engineering, Florida A and M University-Florida State University College of Engineering, 2525 Pottsdamer Street,Tallahassee, FL 32310-6046, USAReceived 1 September 2002; revised 10 April 2003; accepted 21 May 2003AbstractThe Resin Infusion between Double Flexible Tooling (RIDFT) technique is a novel two-stage process, which incorporates resin infusionand wetting with vacuum forming. The flow front of the infused resin is two-dimensional and avoids flow complexities prevalent in the three-dimensional flow seen in other liquid composite molding techniques. It employs a one-sided mold, which provides obvious cost benefitswhen compared with resin transfer molding. On-going prototype development of the RIDFT process has yielded positive results. Compositelaminates with good surface quality, micro structural characteristics, and mechanical properties have been repeatedly produced with costsavings of 24% when compared with SCRIMP. This paper describes the RIDFT process, outlining its merits and presenting its challenges,whilst identifying potential benefits to industry. Current work being undertaken include the refining of production parameters, theconstruction of a larger prototype to examine the full extent of its suitability for the manufacture of large composite components and theincorporation of the UV curing technique to reduce the cycle time in the manufacture of large structures.Keywords: E. Forming; Infusion1. IntroductionThe transport sector continues to provide significantgrowth opportunities for polymer composites with advan-tages of weight savings, corrosion resistance and functionalintegration 1. However, the available production processeshave limited the utilization of composite materials in themass production sector. Many of the current processes donot readily lend themselves to mass production due to longcycle times and high emissions of harmful volatile organiccompounds (VOCs). Nevertheless, liquid composite mold-ing (LCM) techniques are technologically promising.Examples include resin transfer molding (RTM), flexibleresin transfer molding (FRTM), and resin infusion byflexible tooling (RIFT). These closed molding techniquesalso have the advantage of reducing emissions of VOCs by90% 2.Cost is a primary consideration in the development ofcomposite production processes. The marine industrymanufacturers have stuck to the validated and cheaperopen molding technique of hand lay-up, despite the USEnvironmental Protection Agency (EPA) regulations. Thedevelopment of the Resin Infusion between Double FlexibleTooling (RIDFT) technique further advances resin infusiontechnology, reducing the higher costs of closed moldmethods.2. Liquid composite molding processes2.1. Resin transfer molding (RTM)Traditionally, RTM has been used as the choice for themanufacturing of composite parts. RTM offers manyadvantages over other processes for the manufacturing offiber-reinforced thermosetting polymer composites. Theseadvantages include improved component thickness toler-ances, better surface finish, and reduced emissions ofvolatiles. One of the critical issues for the success of RTMprocesses is the proper understanding and prediction of resinflow during mold filling. Considerable work has been donein this area and some models and simulation tools areavailable 37. Nonetheless, the analysis of resin flow forparts with complex geometry and permeability variationsstill present difficulties. However, preform preparation andComposites: Part A 34 (2003) 803811*Corresponding author. Tel.: 1-850410-6352; fax: 1-850-410-6342.E-mail address: (O.I. Okoli).tooling costs can be prohibitively large for parts of morethan a few meters in dimension, particularly for one-off orsmall production runs when compared with the hand lay-upprocess 8. Fig. 1 shows a schematic of the RTM process.Further development of LCM processes have been targetedat reducing complexity and associated costs. Some of thesewill be discussed in the following sections.2.2. Resin infusion under flexible tooling (RIFT)Resin Infusion under Flexible Tooling (RIFT) is arelatively new process, introduced in the 1980s. A versionof RIFT dates back to the 1950s when it was used in theproduction of boat hulls. Fig. 2 shows the RIFT processdeveloped by Ciba and Geigy 9. A flexible female splashtool was the basis behind this process. During the 1980s,the use of a rubber bag as the flexible tool was investigatedand several patents were filed 8. The process wasrediscovered during the 1990s and has found applicationparticularly in the marine and automotive industries. Aversion of RIFT is used to strengthen offshore structureswith carbon fiber 8.In the RIFT process, fibers are first placed onto afemale mold that is typically coated with a release agent.Next, a flexible tooling layer is placed over the fiber andsealed around the edges vacuum tight. The fiber is thenvacuum infused between the mold and flexible tooling layer,thereby forming the shape of the part.RIFT retains many of the environmental advantages ofRTM, but at a much lower tooling cost, since half of theconventional rigid closed mold is replaced by a bag.Adapting existing contact molds for the RIFT processmay be feasible. This becomes very important in massproduction, as there isa potential for millions ofdollars to be saved from reduced tooling and manufac-turing costs.RIFT has some disadvantages over the RTM process.RIFT offers limited direct control over the thickness or fibercontent of the final composite laminate in the RIFT process.These parameters depend on the compressibility andrelaxation of the reinforcement under pressure, andinteractions with bagging film breather and other ancillarymaterials 8.Compression studies of dry fiber assemblies have beensubject to much research 8,1015. Pearce and Summers-cales 10 noted that the response of a dry preform wasdynamic. Time dependent compression and relaxation wereobserved, and repeated loading and unloading of thereinforcement achieved higher compaction at a givenpressure. The compression of the reinforcement duringRIFT is further complicated by the arrival of the flowingresin. This provides lubrication for the fibers and may affectthe deformation of the laminate under the vacuum bag.Furthermore, the effective compressive force acting on thereinforcement is not constant during the process. Saunderset al. 15 investigated the compressibility of differentfabrics (plain weave, twill, satin, non-crimped stitch-bonded) and determined that the compressibility of a fabricdepended on its type. Twill weave fabrics were the mostdifficult to compress in the wet and dry states.Before the arrival of the resin at a given point, the drylaminate is subject to atmospheric pressure. As the resinflows past this point, the pressure in the resin rises, so thenew compression on the reinforcement reduces. Theprevailing is indicative of the possibility of flow-induceddefects with an increase in complexity of part geometry. Atheoretical and practical understanding of these compactionmechanisms is required in order to assess whether moldedlaminates can be produced with a consistent, reproducibleand predictable fiber content and quality. Any interactionbetween the laminate and the ancillary materials during theprocess must be quantified 8.Summerscales 9 showed that the RIFT processreduces worker contact with liquid resin while increasingcomponent mechanical properties and fiber content byreducing voidage compared to hand lay-up. Furthermore,RIFT offers the potential for reduced tooling costs wherematched tooling (RTM or compression molding) iscurrently used 9.RIFT has many advantages over the traditional RTMprocess. These advantages include 11:Fig. 1. Schematic of the RTM process.Fig. 2. Schematic of the CibaGeigy RIFT method 4.J.R. Thagard et al. / Composites: Part A 34 (2003) 803811804 Use of existing hand lay-up molds with only minoralterations Low investment in additional equipment Reduced void content (as compared to 3D infusiontechniques) Ability to produce very large componentsNevertheless, part thickness consistency is a problemwith RIFT.2.3. Flexible resin transfer molding (FRTM)A similar process to RIFT is FRTM. FRTM is aninnovative composite manufacturing process, developedbased on detailed cost analysis, which is intended to be costeffective by design. FRTM is a hybrid process, whichcombines the technical characteristics and respectivefavorable economics of diaphragm forming and RTM.Separate sheets of dry fiber and solid resin are placedbetween elastomeric diaphragms and heated so that the resinliquefies. The fiber and resin are then compacted by drawinga vacuum between the diaphragms, and formed to shape bydrawing the diaphragm assembly over hard tooling 16.Fig. 3 shows a schematic of the FRTM process. The FRTMprocess was optimized to produce high quality parts withlow thickness variation, low void content and high fibervolume.Finally, the cost effectiveness of the FRTM process wasverified through a mini-production run 16. FRTM wasdesigned and developed to allow for parts to be madecheaper and faster than traditional methods such as RTM. Aneed for new cost effective means of production is often astarting point for the development of a new process such asFRTM from the classical RTM process. The comparativeadvantages and disadvantages of the vacuum formingversion of FRTM and several other currently availableprocesses such as RIFT are shown in Table 1.Conceptually, FRTM is a hybrid process, whichcombines favorable characteristics of RTM and diaphragmforming. Like RTM, FRTM uses the lowest cost constitutiveraw materials possible (dry fiber and resin), but eliminatesthe labor intensity typically associated with preparation ofthe three-dimensional fibrous preform used in RTM. InFRTM, fabric is formed in a one step double diaphragmforming process. This reduces labor intensity and decreasescycle time. FRTM can also reduce the tooling coststypically associated with RTM because no heavy matchedtooling is required 16.The second advantage of the FRTM process arises fromthe fact that the diaphragm system is, by nature, deformable,and provides a low cost reconfigurable tooling surface.Through the use of various forming methods such asvacuum forming and matched mold stamping, it is possibleto reduce the tooling costs associated with dedicatedmatched tooling in the traditional RTM process. Reducedtooling costs can come from lighter weight tooling, one-sided tools, or through the economic advantages of aflexible, reconfigurable forming mechanism. FRTM alsoreduces or eliminates tool cleaning, which is typically labor-intensive 16.The third advantage of the FRTM process is therepeatability of the impregnation process, which is quickerand more easily controlled. This results from conducting theresin impregnation along the part thickness direction, whichis relatively shorter than the other two in-plane directions.Additionally, by impregnating in the flat, placement ofsprues and vents is independent of final part geometry. Thetraditional costly experimentation necessary to optimizeprocessing variables and redesign tooling to achieve void-free uniform wet-out is eliminated, and development timefor new parts is greatly reduced since new learning is notrequired. Given that the resin begins in a position very closeto its final location, the process is inherently quicker andmore controllable than the transverse impregnation methodtypically associated with RTM 16.Table 1 shows the disadvantages of the FRTM process.Many forming processes have limitations in the geometriesthat can be formed. Undercuts cannot be produced with thevacuum forming mechanism. The control of thicknessvariation and achievable fiber volumes with the FRTMFig. 3. Schematic of the FRTM process 16.Table 1Process comparison chart 16ProcessAdvantagesDisadvantagesHandlay-upCan producecomplex shapesExpensive rawmaterialWell understoodLabor intensiveNot cost effectiveat high volumesRTMUse of low costraw materialLabor intensiveperform preparationProduce complex/highly integrated partsHigh tooling cost3Dflow difficult to controlFormingLabor costis reducedExpensive raw materialOne step bulkdeformationComplexity limitedto formable shapesFRTMand RIFTUses low costraw materialsComplexity limited toformable shapesLess labor content,bulk deformationThickness variationpotential2D impregnationeasier to controlLimits in achievablefiber contentJ.R. Thagard et al. / Composites: Part A 34 (2003) 803811805process is potentially limited. Control of thickness variationis optimized using close loop process control and throughjudicious selection of resins, whose properties were bestsuited for the unique requirements of the FRTM process.Fiber volume is closely related to the compaction pressureapplied to the fabric during cure,therefore, varies dependingon the forming method employed 16.2.4. Vacuum bag molding (VBM) and Seaman compositesresin infusion molding process (SCRIMP)The VBM technique is a closed mold technique and acost-effective alternative to the open mold processes.SCRIMP is a popular version of the VBM. In this process,a network, which consists of grooves or channels, is used todistribute the resin and reduce the flow resistance and fillingtime. The resin fills the grooves or channels first by vacuumpressure, and then the resin infuses into the fiber perform. InVBM, a one-sided rigid mold and a bag are used to form amold cavity 17.The VBM process can be divided into five steps. First, inpre-molding, the mold surface is cleaned, and then a moldrelease agent and a gel coat are sprayed on the surface. Next,during reinforcement loading, dry fiber mats are mountedinto the mold and covered by a flexible bag. The cavity issealed by vacuum tapes or other techniques, and channelnetworks or grooves form. In the third step, the cavity of themold is vacuumed and resin infuses into the fiber mats bythe vacuum force. After the cavity is filled with resin, resinbegins curing and solidifying into the composite part, calledthe resin-curing step. Finally, the cured composite is takenout of the mold, and the next cycle begins 17.2.5. Resin infusion between double flexible tooling (RIDFT)RIDFT intends to solve problems associated with otherLCM techniques. These problems include achievable fibervolume, part thickness consistency, manufacturing cycletime and process complexity. Although not all problemshave been currently addressed, it was the intent of thisresearch to use RIDFT to overcome the shortcomings andlimitations of other LCM techniques. Fig. 4 shows aschematic of the RIDFT process.Unlike the FRTM process, the RIDFT process does notuse dry solid sheets of resin, but currently uses a lowviscosity room temperature curing thermoset. The roomtemperature thermosets can vary hardener content to allowfor partial curing within 10 minutes of completed infusion,which allows for the partially cured part to be removed.Furthermore, the low viscosity resin may provide betterlubrication for reinforcing fibers, thus enhancing processformability.An advantage of the RIDFT process is that the flow ofresin is two-dimensional eliminating the complexity of thethree-dimensional flow front experienced with RTM 18.Other advantages of RIDFT include lower tooling costswhen compared with RTM, reduced production times, theincorporation of UV curing techniques, and the potential forattaining higher fiber contents. The inherent limitationsrestrict the part geometries to formable shapes.An advantage of RIDFT over RIFT is in the use of asecond flexible tooling that reduces cleanup and manufac-turing preparatory work. With RIDFT, resin does notcontact the mold surface and eliminates the need to preparethe mold before each cycle. In addition to reducing amanufacturing step, this does not lend itself to tool wearexperienced from continuous use as seen in the RTMprocess.For the RIDFT process, porous aluminum mold technol-ogy can be utilized. International Mold Steel 19constructed the porous mold seen in Fig. 5 for use withRIDFT. The Swiss manufacturer, Portec, introduced aunique patented material with a trade name METAPOR19. This commercially available product consists ofaluminum granules encased by epoxy resin and compressedunder high pressure. The combination of materials and themanufacturing process results in a cast block having theappearance and feel of solid metal, while being completelymicro-porous and permeable to air 19.Fig. 5. International mold steel porous mold (METAPOR).Fig. 4. Schematic of the RIDFT process.J.R. Thagard et al. / Composites: Part A 34 (2003) 803811806The METAPOR technology allows the RIDFT process toovercome potential problems. The vacuum driven formingstep in the RIDFT process is the key to forming part shapes.Micro-pores in the mold allows for vacuum to be pulledfrom all areas within the mold, which allows part intricacyto be increased, as problems associated with air pockets areno longer an issue.Fig. 6 shows that when using a non-porous mold thevacuum cannot form the flexible layer into the V-shapedgroove. Once the vacuum is evacuated from between thenon-porous mold and the silicone sheet, the forming can nolonger occur. However, with the porous mold surface the airis evacuated from all areas on the mold surface and allowsfor the silicone sheet to form into the V-shaped groove. Dueto low forming pressures and the lack of contact between theresin and the mold surface, RIDFT mold cost is significantlyless than with other liquid molding processes.3. Modeling of RIDFT formingUnderstanding the forming mechanics and the predictionof the formability of desired geometries within the RIDFTprocess necessitates the creation of a simulation model. TheRIDFT process is dynamic and simulation software must bechosen that can account for various materials used withinthe process, interactions of these materials and the forceapplied during forming. The current effort will investigatethe PAM-FORM software since it is a general-purpose finiteelement package for the industrial virtual manufacturing ofnon-metallic sheet forming.3.1. Materials propertyWithin the PAM-FORM simulation model of the RIDFTprocess, the following three distinct material types wereused and defined 20. Material type 121 for the flexible silicone sheets Material type 140 for the fiber reinforcement Material type 100 for tooling and vacuum chamber3.1.1. Material type 121 for the flexible silicone sheetsThe material model is characterized as nonlinear thermo-visco-elastic for shell elements (GSell Model). Inputs forthis material model include initial thickness, Youngsmodulus, Poissons ratio, and mass density. The governingequation used within the PAM-FORM software is given inEq. (1) 20.s k1 2 exp2vEexphE2Em1where,kscaling factor or material consistency in softwaremodel1 2 exp2vE visco-elastic term for low E (strain)exphE2 strain hardening for high E (strain)Emstrain rate sensibilitymstrain rate hardening exphstrain hardening coefficientEmodulus of the wetted fabrics3.1.2. Material type 140 for the fiber reinforcementThe material model is characterized as thermo-visco-elastic matrix with elastic fibers for shell elements. Inputsfor this material model include the following 20: Material density Locking angle from a picture frame test Youngs Modulus in 0 and 908*Stress vs. strain curves in 0 and 908 at different strainrates Shear modulus using picture frame test or stress vs. strainin 458*Stress vs. strain curves in 458 at different strain rates*Perform picture frame test to calculate shear modulusG Effective viscosity using picture frame testF SmdEdt2whereSfabric surface areadtshear strain ratemeffective viscosity Bending factor3.1.3. Material type 100 for tooling and vacuum chamberThe material model is characterized as null material forshell elements. The null material for shells is a convenientand economic tool for the modeling of contact surfaceswhen internal forces and deformations of these surfaces arenot of interest 21.Fig. 6. Porous and non-porous mold surfaces for use with RIDFT.J.R. Thagard et al. / Composites: Part A 34 (2003) 8038118073.2. Defining contact interfacesContact interfaces within the PAM-FORM software areused to define the interactions that occur within thesimulation model. For the RIDFT simulation model thereare four contact interfaces that occur and are listed asfollows: Fiber layer-to-fiber layer interface Fiber layer-to-silicone interface Silicone-to-silicone interface Silicone-to-tooling interfaceThese interfaces can be characterized within the model-ing software by use of two primary contact interface typesand two secondary contact interface types. The interfacetypes include the following 21: Type 16 Lagrangian contact-silicone-to-tooling interface Type 15 Contact blank/tool-silicone-to-tooling interface Type 33 Surface/surface-fiber-to-fiber, fiber-to-silicone,silicone-to-silicone interfaces Type 13 Bilateral contact-fiber-to-fiber, fiber-to-silicone,silicone-to-silicone interfaces3.2.1. Type 16 Lagrangian contact for flexible silicone sheetto tooling surface interfaceThe contact treatment used for this interface is the bucketsearch. The bucket search method is used to determine whencontact between the flexible silicone sheet and the toolingsurface has occurred. Fig. 7 shows the bucket searchapproach. If the silicone passes the tool, it is displaced backaway from the tool equal to the distance the tool wasviolated. This enforcement keeps the silicone from passingthe tool within the simulation model.3.2.2. Type 15 Contact blank/tool for flexible silicone sheetto tooling surface interfaceCritical input parameters for this contact interfaceinclude friction, penalty, search frequency and contactdamping. The search frequency refers to how often themodel searches for the contact between the flexible siliconesheet and the tooling surface.The contact treatment used for this interface is abucketsearchasshowninFig.7.Thecontactenforcement used for this interface is the penalty contact.The contact enforcement addresses how, if the siliconepasses the tool surface, the silicone is moved back awayfrom the tool. This may occur if the movement of theflexible silicone sheet between time steps and searchfrequency allows it to travel past the tool. The penaltycontact works by assessing a penalty value within thecontact interface. This penalty value is used to apply aforce normal to the tool, to force the silicone back fromthe tool surface. Eq. (3) shows the contact penalty, whileFig. 8 shows the contact penalty.F pd3whereppenalty valueddistance silicone has violated the tool3.2.3. Type 33 surface/surface and type 13 bilateral contactThese contact interface models are used to describe theinterface between the fiber-to-fiber contact, fiber-to-siliconecontact and silicone-to-silicone contact surfaces. Criticalinput parameters for these contact interfaces includefriction, thickness, penalty, search frequency and stiffnessdamping.The contact treatment used for these interfaces is theconnectivity search. The connectivity search method isused to determine when contact between fiber-to-fiber,fiber-to-siliconeandsilicone-to-siliconesurfaceshasoccurred. This search is performed according to thesearch frequency,calculating whether nodes oftheflexible silicone sheet have contacted the tool surface.According to the connectivity search, contact will happenwhen the node is half the thickness of the silicone awayfrom the tool surface. Fig. 9 shows the connectivitysearch. The contact enforcement used for these interfacesis the penalty contact.Fig. 7. Bucket search approach 20.Fig. 8. Contact penalty 20.J.R. Thagard et al. / Composites: Part A 34 (2003) 8038118084. Prototype development4.1. Current prototypeThe initial RIDFT prototype allows for part constructionwith dimensions of 1 foot (0.3 m width) 2 feet (0.6 mlength) 1 foot (0.3 m depth). The process is as describedin Fig. 4. The machine is constructed using a mild steelframe and mild steel walls for the vacuum chamber withsealing frames constructed from aluminum.The initial parts manufactured using the RIDFT processare missile quarter panels. The mold used is shown in Fig. 5.The finished panels are shown in Fig. 10.4.2. Micro-structural evaluation and mechanical propertiesGood wetting and interfacial bonding are indicative ofthe mechanical properties of the resulting compositecomponent 22. Fig. 11 is an environmental scanningelectron microscope (ESEM) image of a RIDFT component.It shows that the RIDFT process, as with other proven LCMtechniques, allows for proper resin penetration of the fiberswith a resulting enhancement of the fibermatrix interfacialbond. In Fig. 12, fragmented matrix parts can be seenbetween the knitted yarns. This indicates that properpenetration of the resin occurred during the RIDFT process.Furthermore, in Fig. 13, a bunch of fibers can be seen heldtogether by the damaged matrix. This is indicative of goodfibermatrix bonding.Tensile tests were performed according to ASTM D3039 23 to ascertain the strengths of the RIDFTcomponents. The strain measurements were made usinganextensometer.Thespecimendimensionswere200 mm 25 mm. Aluminum end tabs 1 mm thick and50 mm long were locally bonded onto the specimenswith Loctite Extra Time Epoxy, leaving a gauge sectionof 100 mm. A bi-directional E-glass fabric and a vinylester matrix were used. The resulting tensile strength was304 MPa, with a Youngs modulus of 19 GPa. The fibervolume fraction was 51%.Fig. 9. Connectivity search approach 20.Fig. 10. Component panels manufactured with RIDFT.Fig. 11. Microstructure of the failed surface of a component made by theRIDFT process showing good wetting of fibers.Fig. 12. Microstructure of the failed surface of a component made by theRIDFT process showing resin penetration of the knitted yarns indicatinggood wetting of the fibers.J.R. Thagard et al. / Composites: Part A 34 (2003) 8038118095. Economic evaluationIn order to ascertain the viability of the RIDFT processfor the manufacture of component parts, a cost comparisonwas made with SCRIMP. The comparison was based on thepart geometry shown in Fig. 14 and a production quantity of250 parts per year. The labor rates were estimated at $14.25per hour (direct) and $ 21.66 per hour (overhead). Thecomponent materials were glass fiber and polyester resin.The estimated fiber content was 50% by volume.The results of the cost analysis between the RIDFTprocess and SCRIMP are shown in Table 2. As can be seen,in all the categories except the hardware (equipment) cost,the RIDFT process has a cost advantage, yielding in anoverall advantage of 24%. Moreover, due to economy ofscale, an increase in production quantities from theprojected 250 parts per year will reduce the 16%disadvantage. A commercial software the CFA ProductionCost Estimator was used in the analysis.6. Ongoing enhancements6.1. Large machine constructionThe current RIDFT prototype has been successful inproducing flat panels and curved panels as shown inFig. 10. Although the ability to produce parts on a smallscale shows promise for the RIDFT process, its successand marketability will depend its ability to manufacturelarge-scale components. This has driven the need for theconstruction of a larger RIDFT machine that is capableof manufacturing parts with dimensions of 5 feet (1.5 mwidth) 10 feet (3 m length) 1 foot (0.3 m depth).The manufacturing of a larger RIDFT machine iscurrently in process. The larger machine has overalldimensions of 10 feet (3 m width) 15 feet (4.6 mlength) 4 feet (1.2 m height). The construction of themain vacuum chamber is already complete.It is widely recognized 24 that the ease with which acomposite can be shaped into a given geometry stronglydepends on the architecture of the reinforcing fiber.Formability assessment studies are ongoing to evaluate thedifferent types of fabrics that are suited to the RIDFTprocess. This study is imperative to avoid associatedproduction problems such as wrinkling of the fibers.6.2. Incorporation Of ultraviolet (UV) curingUV curing will provide several important advantageswhen combined with the RIDFT process. The resin onlycures with the presence of intense UV light. This allows forcomplete forming without the concern of gel times as withmost vinyl ester resins. Once the shape has been formed, theUV light can then be applied and the part quickly cured.This is facilitated by the use of silicone sheets as the flexibletooling layer, which allow for the transmission of UV lightthrough the tooling surface. This results in the reduction ofprocess cycle times since UV curing provides for acceler-ated curing times. The shortened curing times is of obviousbenefit to industry, especially in the mass production sector.Fig. 13. Microstructure showing failed fibers held together by the damagedmatrix, indicating good fiber-matrix bonding.Table 2Cost analysisSCRIMP ($)RIDFTReduction (%)Raw materials266.22262.711Consumable materials71.7644.9937Tooling amortization24.804.5082Hardware53.0061.40216Labor (with overhead)428.12246.4742Non-production77.8077.800Cost/lb6.184.6824Total cost921.70697.8724Fig. 14. Composite part geometry.J.R. Thagard et al. / Composites: Part A 34 (2003) 8038118107. ConclusionThe construction of the RIDFT prototype was based onthe need to further advance resin infusion technology. As avariation of the RIFT process, RIDFT offers additionaladvantages while maintaining advantages of the RIFTprocess. With the addition of a bottom flexible toolingsurface, the cleanup and pre-manufacturing preparatorywork is reduced. With the RIDFT process, resin contact withthe mold surface does not occur and eliminates the need toprepare the mold before each cycle. In addition to reducing amanufacturing step, this does not lend itself to tool wearexperienced from continuous use.In ascertaining the cost effectiveness of the RIDFTprocess, a comparison was undertaken between RIDFT andSCRIMP. Preliminary results indicated a cost savings ofabout 24% in favor of the RIDFT process.Ongoing development of the RIDFT process aims tovalidate the ability for the manufacture of large compositecomponents and the red
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