This document summarizes the monocoque frame design for the Cornell FSAE racing team. It includes details on the laminate layup schedule using various carbon fiber prepreg materials and core. It describes material property tests and results. Finite element analysis was conducted to evaluate stresses, strains, and stiffness. Physical tests on frame sections match the analytical predictions of strength and stiffness. The monocoque meets the team's goals for lightweight strength and torsional rigidity.

1. Cornell FSAE
Monocoque Frame Overview
Alex Hsia
Cornell FSAE Monocoque Designer ’14

4. Layup Order
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Side Impact
Bulkhead
Support
Front Hoop
Bracing
Main Hoop
Support
Lip Rear
(Shoulder
Harness Bar) Bulkhead Engine Top Bottom Back Damper Lip Front
Lip Corners
Front Lip Thin
Lip Corners
Rear
1 T800H,45 T800H,45 T800H,45 T800H,45 T800H,45 T800H,45 T800H, 45 T800H, 45 T800H, 45 T800H, 45 T800H, 0 T800H, 0 T800H, 0 T800H, 0 1
2 T800S, 0 T800S, 0 T800S, 0 T800S, 0 T800S, 0 T800S, 0 T800H, 0 T800H, 0 T800H, 0 T800S, 90 T800H, 0 T800H, 0 T800H, 0 T800H, 0 2
3 T800S, 90 T800S, 90 T800S, 90 T800S, 90 T800S, 0 T800H,45 T800H, 45 T800H, 45 T800H, 45 T800S, 0 T800H, 0 T800H, 0 T800H, 0 T800H, 0 3
4 T800S, 0 T800S, 0 T800S, 0 T800S, 0 T800H,45 T800S, 0 .5 Core .5 Core T800H, 0 T800S, 90 T800H, 45 T800H, 45 T800H, 45 T800H, 45 4
5 T800H,45 T800H,45 T800H,45 T800H,45 0.75 Core T800H,45 T800H, 45 T800H, 45 T800H, 45 T800H, 45 T800H, 45 T800H, 0 T800H, 45 T800H, 45 5
6 1 Core 1 Core .5 Core 0.75 Core T800H,45 T800S, 0 T800H, 0 T800H, 0 T800H, 0 T800H, 0 .5 Core T800H, 45 T800H, 0 T800H, 45 6
7 T800H,45 T800H,45 T800H,45 T800H,45 T800S, 0 T800S, 0 T800H, 45 T800H, 45 T800H, 0 T800H, 45 T800H, 45 T800H, 0 T800H, 0 T800H, 0 7
8 T800S, 0 T800S, 0 T800S, 0 T800S, 0 T800S, 0 T800H,45 T800H, 45 0.75 Core T800H, 45 T800H, 45 T800H, 45 T800H, 0 8
9 T800S, 90 T800S, 90 T800S, 90 T800S, 90 T800H,45 0.75 Core T800H, 0 T800H, 45 T800H, 0 T800H, 0 T800H, 45 T800H, 45 9
10 T800S, 0 T800S, 0 T800S, 0 T800S, 0 T800H,45 T800H, 45 T800H, 0 T800H, 0 T800H, 0 T800H, 0 T800H, 45 10
11 T800H,45 T800H,45 T800H,45 T800H,45 T800S, 0 T800H, 0 T800H, 45 T800H, 0 T800H, 45 T800H, 0 T800H, 45 11
12 T800S, 0 T800H, 45 T800S, 90 T800H, 0 T800H, 0 T800H, 0 12
13 T800H,45 T800S, 0 T800H, 45 T800H, 0 13
14 T800S, 0 T800S, 90 T800H, 0 T800H, 0 14
15 T800H,45 T800H, 45 T800H, 45 15
16 T800S, 0 T800H, 0 16
17 T800H,45 T800H, 0 17
18 T800H, 0 18

5. Material Properties Tests

6. -100
0
100
200
300
400
500
600
700
800
0 0.005 0.01 0.015 0.02 0.025
Load(lbf)
Displacement
T800H [05] Tensile Coupons
Sample 1
Sample 2
Sample 3
-100
0
100
200
300
400
500
600
700
800
-0.005 0 0.005 0.01 0.015 0.02 0.025
Load(lbf)
Displacement
T800S [05] Tensile Coupons
Sample 1
Sample 2
Sample 3
Tensile strip modulus tests, T800H and T800S
Specimens were not broken in order to re-test to check for slippage in jaws

7. -100
0
100
200
300
400
500
600
700
800
900
0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02
Load(lbf)
Displacement
M46J [05] Tensile Coupons
Sample 1
Sample 2
Sample 3
-100
0
100
200
300
400
500
600
700
0 0.005 0.01 0.015 0.02 0.025
Load(lbf)
Displacement
T300 [05] Tensile Coupons
Sample 1
Sample 2
Sample 3
Tensile strip modulus tests, M46J and T300

8. Tensile strip strength tests, T800H, T800S
0
500
1000
1500
2000
2500
3000
0 0.05 0.1 0.15 0.2 0.25
Load(lbf)
Displacement (in)
T800H [03] Tensile Coupons
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4
Load(lbf)
Displacement (in)
T800S [03] Tensile Coupons
Non-linear curve indicates slipping in jaws

9. 0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
M46JSample1
M46JSample2
M46JSample3
M46JSample4
T300Sample1
T300Sample2
T300Sample3
T800HSample1
T800HSample2
T800HSample3
T800HSample4
T800HSample5
T800HSample6
T800HSample7
T800HSample8
T800HSample9
T800HSample10
T800HSample11
T800HSample12
T800HSample13
T800HSample14
T800SSample1
T800SSample2
T800SSample3
T800SSample4
T800SSample5
T800SSample6
T800SSample7
Modulus(Msi)
Sample
Tested Modulus of Prepreg Material
M46J Sample 1
T300 Sample 1
T800H Sample 1
T800S Sample 1
Tested moduli of materials all much lower than expected. Possible sources of error include slipping in jaws,
compliance in testing apparatus, incorrectly designed test strips.

10. 0
50
100
150
200
250
300
350
400
Strength(Ksi)
Sample
Tested Strength of Prepreg
M46J Sample 5
T800H Sample 12
T800S Sample 5
Tested max strengths are close to expected.

11. 0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
0.018
0.02
Strain(in/in)
Sample
Tested Max Strain of Prepreg
M46J Sample 5
T800H Sample 12
T800S Sample 5
Tested max strains are also close to expected.

13. Rough analysis using ANSYS ACP
Figure 3. 3/4" Solid Carbon Hardpoint Test Panel

14. Hardpoint Analysis

15. Panel Bending and Pullout Tests

16. y = 28102x - 187.03
0
1000
2000
3000
4000
5000
6000
0 0.2 0.4 0.6 0.8
Load(lbf)
Displacement (in)
Hardpoint Test Panels
.75" Hardpoint
Panel 1
,75" Hardpoint
Panel 2
1" Hardpoint
Test Panel
Series1
Linear (Series1)

17. y = 18119x + 21.204
0
1000
2000
3000
4000
5000
6000
0 0.2 0.4 0.6 0.8
Load(lbf)
Displacement (in)
Hardpoint Test Panels
.5" Hardpoint
Panel 1
.5" Hardpoint
Panel 2
Linear (Series1)

18. Factors of Safety over Core Failure
Front Lower Forward 3.859911 Rear Lower Forward 10.34577
Rear 7.427245 Rear 12.20871
Upper Forward 1.280878 Upper Forward 4.753317
Rear 2.530728 Rear 1.757584
Toe link 11.50272 Toe link 8.651866
Pushrod 1.954779 Pushrod 1.68903

19. Boundary Conditions for ANSYS Torsional Stiffness

21. ANSYS model predicts 4800 ft-lb/deg torsional
stiffness

22. Figure 10. "Lozenging" Effect

23. Figure 11. Vector Principal Elastic Strain around Lip

24. y = 1538.5x
-1000
-800
-600
-400
-200
0
200
400
600
800
1000
-0.6 -0.4 -0.2 0 0.2 0.4 0.6
Torque(ft-lb)
Angular Displacement (deg)
Hub-Hub Torsional Stiffness

25. y = 4083.7x
-1000
-800
-600
-400
-200
0
200
400
600
800
1000
-0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2 0.25
Torque(ft-lb)
Angular Displacement (deg)
Monocoque Torsional Stiffness

27. Design goal:
frame stiffness 10x overall torsional wheel rate
Overall
torsional
wheel rate 120 ft-lb/deg
vehicle 1553.03 ft-lb/deg
suspension 2500 ft-lb/deg 12.5x wheel rate
frame 4100 ft-lb/deg 20.5x wheel rate

28. ANSYS Corner Brake Bump

29. Factor of safety of >5 everywhere on body. Max
strain of 18e-3 strain obtained from tensile tests

30. Stress Contour

31. patch load 217.5 lbf
upright height 6.7 in
hardpoint stiffness 28000 lbf/in
top A-arm load 89.74449 lbf
lower A-arm load 309.9383 lbf
top hardpoint deflection 0.003205 in
lower hardpoint deflection 0.011069
camber change at max
corner 0.122069 deg
Camber
Compliance due to
hardpoints

32. 3 Point Bend Test Results
y = 6080.6x - 43.689
0
500
1000
1500
2000
2500
0 0.1 0.2 0.3 0.4 0.5 0.6
Load(lb)
Displacement (in)
3 Point Bend C
y = 6946.3x - 415.24
0
500
1000
1500
2000
0 0.1 0.2 0.3 0.4 0.5 0.6
Load(lb)
Displacement (in)
3 Point Bend A
y = 7586.5x - 57.412
0
500
1000
1500
2000
2500
0 0.1 0.2 0.3 0.4 0.5 0.6
Load(,bf)
Displacement (in)
3 Point Bend B

33. Manufacture Pictures

34. Core Sections and Core Splice

35. Figure 14. Three part cure (2 autoclave, 1
postcure) for improved surface finish

36. Cured Laminate