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Viscoelastic Measurement Viscoelastic Measurement as a as a
Method for Process ControlMethod for Process Control
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Long Term GoalLong Term GoalChange From:Change From:Time and Temperature Goals with Time and Temperature Goals with
Cure State Assumed Cure State Assumed
To:To:Cure State Measured Cure State Measured with Time and with Time and
Temperature ManagedTemperature Managed
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Lab Equipment Contemporary to Legacy Lab Equipment Contemporary to Legacy Specification Development ca. 1971Specification Development ca. 1971
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State of the Art Test Equipment and State of the Art Test Equipment and Process ControlsProcess Controls
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Why Viscoelastic Measurements?Why Viscoelastic Measurements?
Before CureBefore Cure•• Storage time & out timeStorage time & out time•• Handling and Handling and LayupLayup•• Staging timeStaging time
During CureDuring Cure•• Infusion Infusion •• Volatile ReleaseVolatile Release•• Consolidation in staged pressure curesConsolidation in staged pressure cures•• Achieve Achieve ‘‘full curefull cure’’
After CureAfter Cure•• Glass transition temperatureGlass transition temperature•• ‘‘Spring backSpring back’’ & & ‘‘FitFit--upup’’•• Fatigue Fatigue
ViscoVisco--elastic Data Used To elastic Data Used To Develop Specifications Develop Specifications
but but Requirements Not Typically Requirements Not Typically
Included In The Included In The SpecificationSpecification
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Time
Tem
pTe
mp
PrePre--Production Process Production Process DevelopmentDevelopment
Testing to set limitsTesting to set limits ViscoVisco--Elastic Elastic boundariesboundaries
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Tem
pTe
mp
Time
Information Conveyed in Specs, T.O.Information Conveyed in Specs, T.O.’’s s and Shop Proceduresand Shop Procedures
Experimental SetupExperimental SetupControl System and RheometerControl System and Rheometer
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Method of Gathering DataMethod of Gathering Data
Production Control System modified toProduction Control System modified to::Provide setProvide set--points to analytical points to analytical instrumentsinstruments
in real time during a controlled production run in real time during a controlled production run post runpost runfrom imported data from imported data
Control of the processing equipment and Control of the processing equipment and the instrument using data from eachthe instrument using data from each
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CSS300 Control SystemCSS300 Control System
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Test Unit & SpecimenTest Unit & Specimen
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Test CellTest CellUpper Die is a load cell and Lower Die Upper Die is a load cell and Lower Die
cycles torque on sample to a specified cycles torque on sample to a specified strain or load. Gstrain or load. G’’ & G& G”” reported. Dies are reported. Dies are heated and grooved for grippingheated and grooved for gripping
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Viscosities of Common MaterialsViscosities of Common MaterialsMaterialsMaterials
CentipoiseCentipoise(cps)(cps)
Poise (Poise (psps)) PascalPascal--sec (Pa.s)sec (Pa.s)Poiseuille (PI)Poiseuille (PI)
ConsistencyConsistency
AirAir 1.00E1.00E--0303 1.00E1.00E--0505 1.00E1.00E--0606 GaseousGaseous
WaterWater 1.00E+001.00E+00 1.00E1.00E--0202 1.00E1.00E--0303 FluidFluid
Olive OilOlive Oil 1.00E+021.00E+02 1.001.00 1.00E1.00E--0101 LiquidLiquid
GlycerinGlycerin 1.00E+031.00E+03 1.00E+011.00E+01 1.001.00 LiquidLiquid
Golden Golden SyrupSyrup
1.00E+051.00E+05 1.00E+031.00E+03 1.00E+021.00E+02 Thick FluidThick Fluid
Polymer Polymer MeltsMelts
1.0E+051.0E+05--1.0E+091.0E+09
1.0E+031.0E+03--1.0E+071.0E+07
1.0E+021.0E+02--1.0E+061.0E+06
ToffeeToffee--LikeLike
PitchPitch 1.00E+121.00E+12 1.00E+101.00E+10 1.00E+091.00E+09 StiffStiff
GlassGlass 1.00E+241.00E+24 1.00E+221.00E+22 1.00E+211.00E+21 RigidRigid
1000 cps = 10 poise = 1 Pa.s = 1 PI
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Typical Cure Path GTypical Cure Path G’’vsvs
Time and Temperature Time and Temperature
227.0
100200
300Temperature Profile Target[Temperature(°F)]
0
5M
10M
15M
20M
25M
G p
0100
200300
400500
Run Time[Time (mins)]
Cure Path of G'TC25 of selected Cure
Softens & Grips
Softens as HeatsCures over Time
G’ rises as cools
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Typical Data from Replication of Typical Data from Replication of Shop Process in AutoclaveShop Process in Autoclave
Temperature
Elastic Modulus G’Loss Modulus G” ~ viscosity
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EndEndQuestionsQuestions
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Experimental GoalsExperimental Goals
Execute Cure State Feedback ScenariosExecute Cure State Feedback ScenariosManage viscosity for infusionManage viscosity for infusion
Keep viscosity constant by increasing temperature Keep viscosity constant by increasing temperature
Correlate DiCorrelate Di--Electric Analysis to ViscosityElectric Analysis to ViscosityProvide greater relevance to process Provide greater relevance to process
Manage PostManage Post--cure cure Develop heat rate data that would prevent reDevelop heat rate data that would prevent re--softening of the part or toolsoftening of the part or tool
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Logic for Managed Infusion Logic for Managed Infusion ViscosityViscosity
1.1. Raise temperature until viscosity (GRaise temperature until viscosity (G””) drops to ) drops to a specified viscosity minimum a specified viscosity minimum
2.2. Stop temperature rise until cure causes Stop temperature rise until cure causes viscosity to raise to a specified maximumviscosity to raise to a specified maximum
3.3. Resume heating and repeat steps 1&2 until Resume heating and repeat steps 1&2 until maximum cure temperature is reached.maximum cure temperature is reached.
4.4. StopStopIf this were an actual part, the run would be If this were an actual part, the run would be
continued until the part were fully cured continued until the part were fully cured
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Managed Viscosity CureManaged Viscosity Cure
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Control Logic for DEA CalibrationControl Logic for DEA Calibration
1.1. Temperature data from a cure cycle that had Temperature data from a cure cycle that had been monitored by DEA was providedbeen monitored by DEA was provided
2.2. Data was loaded into the CSS300 Post Data was loaded into the CSS300 Post Process Analyzer Process Analyzer
3.3. The temperature cycle was duplicated on the The temperature cycle was duplicated on the rheometerrheometer
4.4. Viscosity data was plotted on graph with DEA Viscosity data was plotted on graph with DEA datadata
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Temperature Replication of Cure Temperature Replication of Cure Monitored by DEA Monitored by DEA
Comparison of 977 Film between RDA-III and DEA Data
0.1
1
10
100
1000
10000
100000
0 50 100 150 200 250 300
Time (min)
RD
A-II
I η' a
nd D
EA R
eadi
ngs
0
40
80
120
160
200
Tem
pera
ture
(°C
)
Rheometer Viscosity inPa.sec
DEA
Boeing Temperature Readings
Avpro Temperature Readings
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Cure Monitored by DEACure Monitored by DEARescaled to Match GraphsRescaled to Match Graphs
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Tooling/Prototype Cure CycleTooling/Prototype Cure Cycle1.1. Initial cure was set at 200F Initial cure was set at 200F (to avoid problems with soft tooling and steam (to avoid problems with soft tooling and steam
outout--gassing)gassing)
2.2. Hold at 200F until GHold at 200F until G’’ near maximum value at specified near maximum value at specified temperaturetemperature
3.3. Raise temperature until a small drop in GRaise temperature until a small drop in G’’ is notedis noted4.4. Begin a hold until GBegin a hold until G’’ recovers to near maximumrecovers to near maximum5.5. Repeat steps 3 & 4 until final cure temperature is Repeat steps 3 & 4 until final cure temperature is
reachedreachedFor actual parts the cure would be continued as specified For actual parts the cure would be continued as specified
to achieve full cure.to achieve full cure.
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Maintain GMaintain G’’ Modulus on Post CureModulus on Post Cure
Note Non-Linear Heat Rate
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SummarySummary
Time/TemperatureTime/TemperatureUsed to control properties but there is no Used to control properties but there is no visibility on the properties controlledvisibility on the properties controlled
ViscoVisco--Elastic Monitoring & ControlElastic Monitoring & ControlTime and temperature still critical to managing Time and temperature still critical to managing material statematerial stateViscoelastic feedback provides opportunity for Viscoelastic feedback provides opportunity for process improvement and corrective actionprocess improvement and corrective actionMSM provides a basis for time and temperature MSM provides a basis for time and temperature adjustments without compromising qualityadjustments without compromising quality
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ConclusionsConclusionsTools exist to measure and manage viscoelastic Tools exist to measure and manage viscoelastic propertiespropertiesTools have Immediately value for development, Tools have Immediately value for development, tooling and discrepancy dispositiontooling and discrepancy dispositionNo significant additional shop requirementsNo significant additional shop requirementsCertified structures are not harmed by MSM Certified structures are not harmed by MSM proceduresprocedures
Certification of structures based on material state Certification of structures based on material state properties desirable but will require additional properties desirable but will require additional work and substantiation work and substantiation