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
1
Background & Motivation
Alternate process development of a high strength part



Weight reduction
Functional performance improvement
Machining time reduction
Cycle time – minutes
Strength – equal to quasi
isotropic
2
Ref : Lambolab.com, composites world
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
3
Importance of closed mold and short fibers
Advantageous closed mold process
Open mold
continuous fiber
Closed mold
short fiber
• Directional properties
• High process time
• High skill requirement
• Intricate shapes not feasible
• High part cost
• Low volume
• 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
4
Compression molding
Minimal flow  Less fiber breakage
5
Ref : Duqueine, Mazumdar composites mfg,
lamborghini urus
Compression molded parts
6
Ref : Hexcel, Lamborghini, Audemars piguet, Carbon Forge, Duqueine, excel sports, DUC -helices
Process dependency
Part  Material  Process
PART
Moldability
Thickness variation
MATERIAL
fiber content
Part
strength
resin type
fillers
formability
volume
Holes or mash off
zones
resin process
parameters
charge placement
fiber
length
process temperature &
pressure
COMPRESSION
MOLDING
Thermal system
Mold design
Press parallelism, mold finish,
ejection
PROCESS
7
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
750 lb
– Normal reaction load
600 lb
Braking Load
– Braking load
600 lb
– Normal reaction load
600 lb
Braking
force
Ref : UTA FSAE team (load values)
Reaction
force
due to 8
weight
Raw material selection
Benchmark properties – Al 6061 T6
• Market study
• Hexcel, ten cate,
Quantum composites
• 15 compounds
•Carbon epoxy and
vinyl ester
SMC market study
12
10 10 10
10
10
10
9
8
9
8
6
7
5.5 5.5
4.35
4
2
0
Al 6061 T6
HexMC
MS 1H
MS 4A
Tensile modulus msi
Compressive modulus msi
Flexural modulus msi
9
Existing wheel center – lateral load
FOS – 0.96
Elements
51831
60157
70013
93733
Equiv Stress (ksi)
36.4
38.9
41.1
41.6
Change %
6.8 %
5.5 %
1.2 %
Deformation – 0.049”
10
Existing wheel center – Braking load
Deformation – 0.004”
11
Inference
• Functional issue
– Increase lateral stiffness
– Strengthen riveting points
• Moldability
– Provide drafts
– Minimize pattern holes
– Gradual thickness variation
L
12
Proposed design
Proposed
Existing
Other
designs
studied
13
Proposed design – Lateral load
>25 % Improvement
FOS - 0.96
27 %
FOS – 1.48
Stress
30 %
14
Proposed design – Braking load
15
Results comparison
Stress (ksi)
45
Deformation (in)
41.6
0.049
0.06
30.5
0.035
30
0.04
Existing
9.0
15
4.0
Proposed
0
0.02
0.004
0.004
0
Lateral
Lateral
Braking
Braking
Weight (lb)
1.52
Proposed
Existing
1.98
0.00
0.50
1.00
1.50
2.00
24 %
16
Mold design
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”
17
Heating system
Cartridge heaters
Quantity – 4/mold
Capacity – 450W
Wattage required for heating the
mold in 30 min – 3.6 KW
18
Heating system - analysis
Minimum temperature variation  Uniform heat absorption by charge
19
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
20
Cooling system analysis
Minimum temperature gradient b/w mold halves  Min warpage
Mold temperature Bottom vs Top
120
80
40
0
0
100
200
300
Time (sec)
400
500
T0.5 m/s
600
B 2.5 m/s
Bottom mold temp Vs time
Top mold temperature vs time
160
120
120
40
B 2.5 m/s
0
0
200
400
Time (sec)
600
Temperature deg C
160
80
Temperature deg C
Temperature deg C
160
80
40
T 2.5 m/s
0
0
200
400
600
800
Time (sec)
21
Ref : DSM design guide
Mold assembly
22
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 – 0.015 mm
 Cure time – 20 min
 Press parallelism – 0.001”/ft (recommended values)
23
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
24
Conclusion
• Design
• Analysis
• Engineering drawing
Part
Material
•Process dependency parameters are
identified and analyzed
•Process data sheet preparation
•Future work involves manufacture of
the mold and part
• Material study
• Material selection
Process
• Mold design
• Engineering drawing
• Heating system analysis
• Cooling system analysis
• Process parameters
25
Thank You
Questions and discussion
26
Analysis conditions
Static Structural analysis
Properties
Units
Al 6061 T6
Al alloy
Density
Young’s modulus
Poisson ratio
lb / in3
msi
0.097
10
0.33
Wheel hub,
existing
wheel center
0.0975
10.297
0.33
Parts
Wheel rim
Carbon
epoxy
0.054
8.357
0.3
Proposed
wheel center
27