Design of a Carbon Fiber Composite Monocoque Chassis for a ...

Design of a Carbon Fiber Composite Monocoque Chassis for a Formula-Style Vehicle

Alex Carline Mitchell Hiller Riley Masters

Formula SAE Overview

Monocoque Introduction

Previous Design

Geometric Constraints

Material Selection

Mounts and Inserts

ANSYS Simulations

Testing

Manufacturing

Acknowledgements

Overview

Formula SAE Overview

➢ International collegiate design series sanctioned by the Society of Automotive Engineers (SAE)

➢ Students design, manufacture and race an open-wheel, Formula 1 style car

➢ Static and dynamic events

Monocoque Introduction

➢ A monocoque is a structural “tub” like chassis that replaces a traditional

steel tube space frame

➢ Commonly made from carbon fiber composite sandwich panels

➢ Used in top tier racing, including Formula 1

Monocoque

Complete

Chassis

Full Car Without

Aerodynamics

➢Successful first monocoque design

➢Half monocoque design

• Lighter and stiffer than spaceframe

➢Good driver visibility

➢Small molds

Previous Design - Advantages

Half Monocoque

Line of Sight

BR20 Half-

Monocoque Chassis

Previous Design - Disadvantages

➢Shear suspension loads

➢Did not take full advantage of unregulated layup regions

➢Overbuilt – Overweight

➢Upright driver position

➢Multiple manufacturing defects

BR20 Half

Monocoque

BR20 Cockpit

Check

BR20 Front

Suspension

➢Normal suspension loads

➢Compact packaging

➢Unique damper mounts

Geometric Constraints – Front Suspension

[FRONT]

BR21 Bottom View

BR21 Left Front

Suspension

[FRONT]

Geometric Constraints – Rear Suspension

➢ Aluminum rear end cap

➢ Easily removable engine and

drivetrain

➢ No engine bay floor in case of

leaks

Left ViewBottom

View

Top

Right

View

Top

View

Geometric Constraints – Driver Controls

➢ Improved wheel position

➢ Improved packaging

➢ Lower driver position

➢ Lower CG

➢ Maintained visibility

Drivers

View

7 Ft.

Material Selection

➢ Better or comparable carbon fiber needed

➢ Important material properties compared

➢ Various core materials used

Mounts and Inserts

➢ Composite panel potted inserts used for mounting

➢ Made from high performance thermoplastic, Torlon

➢ Inserted in cleared out hole

➢ Epoxy injected around insert

ANSYS Simulation – Methodology

➢Laminate Design Method

➢ Ideal Results

• FOS of 1.65 minimum

• (1.15 for material imperfections + 1.5 for manufacturing quality)

1• Front Suspension Load Case

2• Rear Suspension Load Case

3• Rollover Load

4• Front Impact

5• Torsional Stiffness

6• Bending Stiffness

Modify Laminate

Run Load Case

Analyze Results

ANSYS Simulation – Load Case

➢Load Case

• 2G turn, 3G bump, 1.5G braking

• Aerodynamic and weight loads

➢Mesh

• High density in load region

1

• Front Suspension Load Case


3• Rollover Load

4• Front Impact



ANSYS Simulation – Load Case

➢Resulting Laminate Regions

• 23 Different Laminate Regions

• High Stress Overlap Regions Defined

➢ANSYS ACP Considerations

• LH and RH versions create 37 different laminates


➢Results – Front Load Case

• FOS: 1.696

• Peak Stress: 67.49 MPa

• Peak Tire Contact Patch Deformation: 2.12mm

➢Isometric View of Results:

1



3• Rollover Load

4• Front Impact



Deformation

FOS

Stress


➢Results – Rear Load Case

• FOS: 1.658


• Peak Tire Contact Patch Deformation: 1.28mm


1



3• Rollover Load

4• Front Impact



Deformation

FOS

Stress


➢Results – Rollover Load Case

• FOS: 3.44


• Load Type: 2G vehicle mass perpendicular to rollover plane


1



3• Rollover Load

4• Front Impact



Setup

FOS

Stress


➢Results – Front Impact Load Case

• FOS: 1.30


• Peak Deformation: 1.374mm

• Load Type: 50kN on Front Bulkhead


1



3• Rollover Load

4• Front Impact



Deformation

FOS

Stress


➢Results – Stiffness

• Target Torsional Stiffness: 3,555 Nm/deg

• Simulated Torsional Stiffness: 6074.16 Nm/deg

• Simulated Bending Stiffness: 113,649 Nm/deg


1



3• Rollover Load

4• Front Impact



Torsional Stiffness Bending Stiffness

𝐾 =2 ∗ 𝐹 ∗ 𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒

𝐴𝑛𝑔𝑢𝑙𝑎𝑟 𝐷𝑒𝑓𝑜𝑟𝑚𝑎𝑡𝑖𝑜𝑛

Torsional Stiffness Equation

Designed Laminate Total Cost and Mass

➢Results:

Testing - Composite Panel Potted Inserts

➢Test jig created for pull test on insert

➢Unable to physically test, but will be conducted at later point

➢Will be conducted on MTS

➢Insert performance seems promising

Testing – 3 Point Bend Tests

➢Method:

➢Panel Test Setup:

Simulation Setup:

Correlation of Results

Simulate in

ANSYS

Create and Test Panel

Analyze Results

Experimental Setup

0

1000

2000

3000

4000

5000

6000

1 2 3 4 5 6

Stiffn

ess (

N/m

m)

Test Sample

Tested Panel Stiffness vs. Simulated

Actual Stiffness (N/mm) (w/o rig compliance) Tested Stiffness (N/mm)

ANSYS Stiffness N/mm)

Manufacturing

➢ Fully comprehensive manufacturing report produced

➢ Guides WMU Bronco Racing Team through step by step process

First Layer of Carbon Fiber

Vacuum Bag

Remaining Layers in First Set of Carbon

Fiber

Vacuum Bag and Cure

Core and Film Adhesive Placement

Vacuum Bag

Core Gap Repairs

First Layer of Second Set of Carbon Fiber

Vacuum BagRemaining Layers of

Carbon Fiber

Vaccuum Bag and Cure

Demold, Trim and Lap Joint

Thank You!

➢Mitch Macdermaid

➢FSAE Team Members

➢Dr. Daniel Kujawski

➢Suraj Nikam

➢Dr. Mitchell Keil

➢Sponsors:

Acknowledgements

Questions?

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