design and analysis of a compression molded carbon composite wheel center vinoth kumar dhananjayan...
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DESIGN AND ANALYSIS OF A COMPRESSION MOLDED CARBON COMPOSITE WHEEL CENTER
VINOTH KUMAR DHANANJAYANThesis Defense for MS Mechanical Engineering
April 3, 2013
Committee :Prof. Robert Woods, University of Texas at Arlington (Advisor)
Prof. Kent Lawrence, University of Texas at ArlingtonProf. Wen Chan, University of Texas at Arlington
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Background & Motivation
Alternate process development of a high strength part
Weight reduction Functional performance improvement Machining time reduction
FORGED COMPOSITE
FORGED CARBON
ADVANCED COMPRESSION MOLDING PROCESS
LAMBORGHINI CALLAWAYCycle time – minutesStrength – equal to quasi isotropic
Ref : Lambolab.com, composites world
3
Objective
•Study on factors influencing the compression molding process
•Analysis of existing and proposed design of a part
•Raw material selection
•Mold design
•Thermal system identification and analysis
•Process parameters
Development of wheel center by compression molding process
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Importance of closed mold and short fibers
• Directional properties• High process time• High skill requirement• Intricate shapes not feasible• High part cost• Low volume
Open mold continuous fiber
• Near isotropic properties• Quicker cycle time in minutes• Minimal skill dependency• Near net shape part and ability to mold complex shapes• Low part cost• High volume
Closed mold short fiber
Advantageous closed mold process
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Compression molding
Minimal flow Less fiber breakage
Ref : Duqueine, Mazumdar composites mfg, lamborghini urus
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Compression molded parts
Ref : Hexcel, Lamborghini, Audemars piguet, Carbon Forge, Duqueine, excel sports, DUC -helices
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Process dependency
COMPRESSION MOLDING
resin type
formability
fiber content
fillers
Mold design
Thermal system
charge placement process temperature & pressure
Press parallelism, mold finish, ejection
Part strength
volumeThickness variation
Holes or mash off zones
Moldability
PART MATERIAL
fiber lengthresin process
parameters
PROCESS
Part Material Process
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Wheel center part study
• Most suitable for compression molding – 20% improvement yields 1.58 lbs weight saving/car
• Improve lateral stiffness – high deformation• High machining time and material wastage• Lateral Load
– Lateral load 750 lb– Normal reaction load 600 lb
• Braking Load– Braking load 600 lb– Normal reaction load 600 lb
Ref : UTA FSAE team (load values)
Reaction force due to weight
Braking force
Wheel center loads
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Raw material selection
Al 6061 T6HexMC
MS 1HMS 4A
0
2
4
6
8
10
12
10
5.5
10
9
10
5.5
9
8
10
4.35
10
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SMC market study
Tensile modulus msi Compressive modulus msi Flexural modulus msi
• Market study
• Hexcel, ten cate, Quantum composites
• 15 compounds
•Carbon epoxy and vinyl ester
Benchmark properties – Al 6061 T6
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Existing wheel center – lateral load
FOS – 0.96
Deformation – 0.049”
Elements Equiv Stress (ksi) Change %51831 36.4 60157 38.9 6.8 %70013 41.1 5.5 %93733 41.6 1.2 %
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Existing wheel center – Braking load
Deformation – 0.004”
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Inference
• Functional issue– Increase lateral stiffness– Strengthen riveting points
• Moldability– Provide drafts– Minimize pattern holes– Gradual thickness variation
L
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Proposed design
Other designs studied
Proposed
Existing
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Proposed design – Lateral load
30 %
>25 % Improvement
FOS – 1.48FOS - 0.96
27 % Stress
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Proposed design – Braking load
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Results comparison
LateralBraking
0
15
30
4541.6
9.0
30.5
4.0
Stress (ksi)
ExistingProposed
LateralBraking
0
0.02
0.04
0.06 0.049
0.004
0.035
0.004
Deformation (in)
Existing
Proposed
0.00 0.50 1.00 1.50 2.00
1.98
1.52
Weight (lb)
24 %
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Mold design
• Mold material - Al 6061 T6– Better machinability– Quick heat transfer– Better surface finish
• Shear edge design – Complete filling– Escape of air
• Mold size– Length 15”– Breadth 14”– Thickness 2.5”
Good mold design Better part quality
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Heating system
Cartridge heaters
Quantity – 4/moldCapacity – 450W
Wattage required for heating the mold in 30 min – 3.6 KW
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Heating system - analysis
Minimum temperature variation Uniform heat absorption by charge
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Cooling system
• Remove heat generated during curing reaction
• Depends on
– Location of cooling lines– Size of cooling lines– Types of cooling lines– Length of cooling circuit– Flow rate of coolant
• Position of channels and time taken for cooling are analyzed in solidworks
• Best suitable mass flow rate of water selected for individual molds to have uniform decrease in temperature
Uniform cooling Minimum warpage
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Cooling system analysis
0 100 200 300 400 500 6000
40
80
120
160
Bottom mold temp Vs time
B 2.5 m/s
Time (sec)
Tem
pera
ture
deg
C
0 100 200 300 400 500 600 7000
40
80
120
160
Top mold temperature vs time
T 2.5 m/s
Time (sec)
Tem
pera
ture
deg
C
0 100 200 300 400 500 6000
40
80
120
160Mold temperature Bottom vs Top
T0.5 m/s B 2.5 m/sTime (sec)
Tem
pera
ture
deg
C
Minimum temperature gradient b/w mold halves Min warpage
Ref : DSM design guide
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Mold assembly
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Process parameters
Material - MS 4A
Charge loading pattern – By trials during manufacturing
Press capacity – 85 ton
Press pressure – 2000 psi
Process temperature – 150 deg C
Mold pre heat time – 30 min
Heater bore clearance – 0.015 mm
Cure time – 20 min
Press parallelism – 0.001”/ft (recommended values)
Accurate control of the process High part repeatability
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Future Scope
• Software simulation to predict– Fiber orientation– Charge pattern– Warpage – Closing speed – Material flow
• Software– Moldex 3d– Cadpress– Express– Autodesk moldflow beta
Process simulation
Animation reference : Moldex 3d
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Conclusion
•Process dependency parameters are identified and analyzed•Process data sheet preparation•Future work involves manufacture of the mold and part
• Design• Analysis• Engineering drawingPart
• Material study• Material selectionMaterial
• Mold design• Engineering drawing• Heating system analysis• Cooling system analysis• Process parameters
Process
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Thank You
Questions and discussion
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Analysis conditions
Properties Units Al 6061 T6 Al alloy Carbon epoxy
Density lb / in3 0.097 0.0975 0.054Young’s modulus msi 10 10.297 8.357Poisson ratio 0.33 0.33 0.3
Parts Wheel hub,
existing wheel center
Wheel rim Proposed wheel center
Static Structural analysis
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