kleineberg dlr spring-in iscm 2008 x

Institut für Faserverbundleichtbau und Adaptronik

ISCM 2008:„Spring-In“ Simulation

M. Kleineberg, T. Spröwitz

Braunschweig, 07.05.2008

Folie 2 > Vortrag > AutorDokumentname > 23.11.2004Institut für Faserverbundleichtbau und Adaptronik

Content:

- Relevance of the “Spring-In” Effect

- Theory of the „Spring-In“ Effect

- Approach to Identify Material Parameters

- FEM Simulation of Complex Curved Profiles

- Conclusion


Content:





- Conclusion


Relevance of the “Spring-In” Effect

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A320 A340-300A340-600

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MD80B757 B767 MD90

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Year of First Fight

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A350XWB

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Substitution ofHigh Volume„Single Aisle“ Models expected in 2015

Expected Production Scenario

- Typical Production Rate: >350 Aircrafts per Year

- Extreme Competition on World Market and therefore Low Earnings per Aircraft

? Composite Airframe only if Mature Production Technologies available

? ?



Crucial Cost Drivers for High Volume Composite Structures

Part Production ? Typically more than 60% of Costs

Component Assembly ? Typically more than 30% of Costs

Derived Measures to ensure Cost Effectiveness

Minimised Rejection Rate ? Maximum Reproducibility on High Level

Minimised Cycle Times ? Optimized utilisation of Technical Equipment

High Precision Manufacturing ? Shim free Assembly



Problem: “Spring-In” Effect causes severe deformations on curved components

? Direct Rejections due to exceeded Shape Tolerances

? Increased Assembling Effort (Shimming) due to increased Gap Distances

? Component Failure or Damage due to Overloading during Assembling

? Component Failure or Damage due to underestimated Mould-Part-Interaction

? Time-Consuming and Expensive Reengineering of Moulds


Content:




- FEM Simulation of Complex Curved profiles

- Conclusion


Theory of the „Spring-In“ Effect

Matrix dominated Out of Plane Properties

Out of Plane Properties: - High Coefficient of Thermal Expansion (CTE)- Noticeable Resin Cure related Effects

In Plane Properties: - Low CTE- Negligible Resin Cure related Effects

Fibre dominated In Plane Properties



( )(1 ) 1

t r t rtot thermal chemical

r r

TT

? ? ? ?? ? ? ?

? ?

? ?? ? ? ?? ?? ?? ? ? ? ? ? ? ?? ?? ? ? ?? ?? ?? ?? ? ? ?? ?

? ? tot????????Total „Spring-In“ Angle ? r: Radial CTE ? t: Tangential CTE ? ? thermal????CTE dependent „Spring-In“ Angle ? r : Radial Laminate Shrinkage ? t : Tangential Laminate Shrinkage ? ?chemical??Cure Shrinkage dependent „Spring-In“ Angle ? T: Effective Temperature Difference

Parameter Definition for a Curved Laminate Section

Calculation Basis

R: Nominal

t: Nominal Laminate Thickness

: Nominal Laminat Angle?

A : Nominal Arc Length, outer/inner o/i

RadiusR’:Radius Measured

t’: Laminate Thickness M

’: Laminate Angle ?

A ’: Arc Length outer/inneroi

easured

Measured

Measured,

RA ’o A’i

Ai

Ao

?

?’

t

R’

t’



Primary “Spring-In” Effects

- CTE in Radial Direction [? r] ? Fibre Volume Content (FVC)- Laminate Shrinkage in Radial Direction [?r] ? FVC- Effective Temperature Difference [? T] ? Process Parameter

Primary “Spring-In” Effects can be Simulated if Coefficients are Available

Secondary “Spring-In” Effects

- Laminate thickness ? Gradient in Degree of Cure- Mould-Part-Mismatch: CTE ? Preload on Boundary Layers- Laminate Imperfections (Voids, Ondulations etc.) ? FVC, Local Stress Induction- Mould-Part-Mismatch: “Spring-In” ? Local Bending Moments- Moisture Expansion of Matrix ? Partial Shrink Compensation- Laminate Radius ? Additional Shear Loads?

Secondary “Spring-In” Effects are difficult to Quantify!



VitrificationGelation

Gelled Glass Region

Sol/Gel Region

Char RegionElastomer Region

Devitrification

Ungelled Glass Region

Liquid Region

Log Time

Tg gel

Tg 0

Tem

pera

ture

Tg Minimum Cycle Time

Minimum„Spring-In“

Time Temperature Transformation (TTT) Diagram for Epoxy Resins



“Spring-In” Effect of L-Shaped Profile

? Independent of Laminate Thickness? Independent of Radius

“Spring-In” Effect of T-Shaped Profiles

? Dependent of Web Thickness? Dependent of Radius

t

Glass epoxy Laminate, L-shaped structure

t

Glass epoxy Laminate, T-shaped structure

Dong, C.; Zhang, C.; Liang, Z.; Wang, B.:

t


Content:





- Conclusion


Approach to Identify Material Parameters

Approach to Simulate Primary “Spring-In” Effects

Standard Parameters for HT fibres and RTM6 Epoxy Resin? Literature, Data Sheets

? r ´(Radial CTE) and ?r (Radial Laminate Shrinkage) ? Experimental Investigation

? T (Difference between Gel-Point and max. Cure Temperature)? Experimental Investigation

Approach to Simulate Secondary “Spring-In” Effects

Avoidance of Secondary “Spring-In” Effects as far as Possible



Strategy to predict “Spring-In” Deformation

Iteration 2D/3DHybridmodel

„Spring-In“ Deformationof Complex Structures

Step 1: Analyses of 90° Coupons under different Process Conditions? Experimental determination of resulting “Spring-In” Angles

Step 2: Adaption of FEM Simulation to measured Results of 90° Coupons? Combined Coefficient for Chemical Shrinkage and Thermal Expansion

Step 3: Simulation of complex Structures by using the identified Combined Coefficient ? Prediction of Assembling Problems and Stress Concentrations

Step 1 Step 2 Step 3



Step 1: Analyses of 90° Coupons under different Process Conditions

0

20

40

60

80

100

120

140

160

180

200

0 100 200 300 400 500 600 700 800 900

T V1, Normal

T V2, Tgel 180°

T V3, Tgel 130°

T V7, Tgel 110°

- Variation of ? T by varying the Gel-Point (110°C, 130°C, 180°C)

- Variation of FVC by varyingthe Mould Gap distance

Ni36 RTM Mould with compatible CTE to reduce Mould-Part-Interaction

Automated Process in a heated Press to increase Reproducibility

High Precision Measuring Equipment to quantify Laminate Thickness and Coupon Angle



Step 2: Adaption of FEM Simulation to measured Results of 90° Coupons

2D / 3D Hybrid FEM Simulation

Each Ply of the Laminate issimulated by 3 Finite Element Layers [Type: HEX8]

2D

3D



Step 2: Adaption of FEM Simulation to measured Results of 90° Coupons


Content:





- Conclusion


FEM Simulation of Complex Curved Profiles

Step 3: Simulation of Complex Structures

2D / 3D Hybrid Models

Integral Z-Profiles

Integral Z-Profiles

Integral LCF-Profiles

UDReinforcedInner andMiddleChord

Profiles that have been investigated



Isostatic Boundary Conditionat Free Edge? Global „Spring-In“ Angle? Stress Analyses

Assembly Boundary Condition

? Stress Analyses

Step 3: Simulation of Complex Structures: Boundary Conditions



Step 3: Simulation of Complex Structures: Simulation Results

Integral Z-Profiles

Integral LCF-Profiles

Global “Spring-In” Effect:? Global Radius Decreases

Global “Spring-In” Effect: ? Global Radius Decreases

Integral Z-Profiles

Global “Spring-In” Effect:? Global Radius IncreasesUD

UD

UD

Stress Level 1:No significant Increase of Stress Level under Assembly BoundaryConditions

Stress Level 2:Stress Level and “Spring-In” Effect can be reduced by 50% by applying low Gel-Temperatures


Content:





- Conclusion


Conclusion

„Spring-In“ Deformation is Highly Dependent on Gel-Temperature and Fibre Volume Content

? Reproducible Process Conditions Required for Cost Effective, High Precision Manufacturing

Simple L-Shaped Coupons can be used to investigate the “Spring-In” Behaviour ofComplex Composite Structures

? Realisation of Spring-In Compensated Manufacturing Moulds possible

Lower Gel-Temperatures lead to reduced “Spring-In” Angles but also increaseCycle Times significantly

? Reduced “Spring-In” Angles indicate a lower Stress Level in the Laminate

kleineberg dlr spring-in iscm 2008 x

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