1. DESIGN AND ANALYSIS OF A COMPRESSION MOLDED CARBON COMPOSITE WHEEL CENTER
VINOTH KUMAR DHANANJAYAN
Thesis 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 Arlington
Prof. Wen Chan, University of Texas at Arlington

2. Background & Motivation
Alternate process development of a high strength part
Weight reduction
Functional performance improvement
Machining time reduction
FORGED CARBON
FORGED COMPOSITE
ADVANCED COMPRESSION MOLDING PROCESS
Cycle time – minutes
Strength – equal to quasi isotropic
LAMBORGHINI CALLAWAY
Ref : Lambolab.com, composites world

3. Objective Development of wheel center by compression molding process
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

4. Importance of closed mold and short fibers
Advantageous closed mold process
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

5. Minimal flow  Less fiber breakage
Compression molding
Minimal flow  Less fiber breakage
Ref : Duqueine, Mazumdar composites mfg, lamborghini urus

6. Compression molded parts
Ref : Hexcel, Lamborghini, Audemars piguet, Carbon Forge, Duqueine, excel sports, DUC -helices

7. Part  Material  Process
Process dependency
Part  Material  Process
COMPRESSION
MOLDING
resin type
formability
fiber content
fillers
Mold design
Thermal system
charge placement
process temperature & pressure
Press parallelism, mold finish, ejection
Part strength
volume
Thickness variation
Holes or mash off zones
Moldability
PART
MATERIAL
fiber length
resin process parameters
PROCESS

8. Wheel center part study
Wheel center loads
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 lb
Normal reaction load lb
Braking Load
Braking load lb
Normal reaction load lb
Reaction force due to weight
Braking force
Ref : UTA FSAE team (load values)

9. Raw material selection
Benchmark properties – Al 6061 T6
Market study
Hexcel, ten cate, Quantum composites
15 compounds
Carbon epoxy and vinyl ester

10. Existing wheel center – lateral load
FOS – 0.96
Elements
Equiv Stress (ksi)
Change %
51831
36.4
60157
38.9
6.8 %
70013
41.1
5.5 %
93733
41.6
1.2 %
Deformation – 0.049”

11. Existing wheel center – Braking load
Deformation – 0.004”

12. Inference Functional issue Moldability L Increase lateral stiffness
Strengthen riveting points
Moldability
Provide drafts
Minimize pattern holes
Gradual thickness variation L

13. Proposed design
Proposed
Existing
Other designs studied

14. Proposed design – Lateral load
>25 % Improvement
FOS – 1.48
FOS
27 %
Stress
30 %

15. Proposed design – Braking load

16. Results comparison
24 %

17. Good mold design  Better part quality
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”

18. Wattage required for heating the mold in 30 min – 3.6 KW
Heating system
Cartridge heaters
Quantity – 4/mold
Capacity – 450W
Wattage required for heating the mold in 30 min – 3.6 KW

19. Heating system - analysis
Minimum temperature variation  Uniform heat absorption by charge

20. Uniform cooling  Minimum warpage
Cooling system
Uniform cooling  Minimum warpage
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

21. Cooling system analysis
Minimum temperature gradient b/w mold halves  Min warpage
Ref : DSM design guide

22. Mold assembly

23. Accurate control of the process  High part repeatability
Process parameters
Accurate control of the process  High part repeatability
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 – mm
Cure time – 20 min
Press parallelism – 0.001”/ft (recommended values)

24. Future Scope Process simulation Software simulation to predict
Fiber orientation
Charge pattern
Warpage
Closing speed
Material flow
Software
Moldex 3d
Cadpress
Express
Autodesk moldflow beta
Animation reference : Moldex 3d

25. Part Material Process Conclusion
Design
Analysis
Engineering drawing
Part
Material study
Material selection
Material
Mold design
Heating system analysis
Cooling system analysis
Process parameters
Process
Process dependency parameters are identified and analyzed
Process data sheet preparation
Future work involves manufacture of the mold and part

26. Thank You
Questions and discussion

27. Analysis conditions Static Structural analysis Properties Units
Al 6061 T6
Al alloy
Carbon epoxy
Density
lb / in3
0.097
0.0975
0.054
Young’s modulus
msi 10
10.297
8.357
Poisson ratio
0.33
0.3
Parts
Wheel hub, existing wheel center
Wheel rim
Proposed wheel center

28. Heating system Uniform temperature distribution  uniform cure
Electric heaters – less expensive, easy installation
Temperature gradient 10 deg c
Types
Cartridge heaters (commonly used)
Strip heaters (suitable for surface heating)
Coil heaters (custom made to suit application)
Wattage required for heating the mold in 30 min – 3.6 KW
(heat required without losses = 3.1 KW +
heat required for the charge = KW+
heat losses = 0.41 KW)
Image ref :

29. Transient Thermal analysis (mold preheat time 30 min)
Analysis conditions
Transient Thermal analysis (mold preheat time 30 min)
Mold – Al 6061
Heaters – SS 304

30. Analysis conditions Fluid flow simulation Heat transfer
coefficient: 25 W/m2/K
External fluid temperature: °C
Fluid -Water
Solid -Aluminum 6061
Time : 10 min
Thermodynamic parameters
Static Pressure: lbf/in2
Temperature: °C
Solid parameters
Default material: Aluminum 6061
Initial solid temperature: °C