AERO Carbon Fiber Monocoque Group B
Zak Codington Jordan Factor Tyler Gold Scott Patterson Mentor: Dr. Mike Cross
Problem Overview Make a carbon fiber monocoque body for the AERO team that is: ● ●
●
Lighter and stiffer than previous frame Drop in replacement to 2014 steel space frame Pass tech inspection at the Formula Hybrid Competition
What is a Monocoque? A monocoque is a chassis that handles all applied loads via the skin.
Why was this proposed? ● Stay current with top ranking Formula Hybrid teams ● Proof of concept for future years ● Compare the different design choices without being forced into one or the other ● Evaluate feasibility with available facilities
Objectives 1. Improve on the current car in weight and stiffness 2. Monocoque must be a drop in replacement that is compatible with the current systems of the car 3. Adhere to all safety and design rules of the 2014 Formula Hybrid rulebook 4. The design must be manufactured in a reproducible manner
Design Overview ● Simple curves ○ Simplify manufacturing
● Draft angle ○ Allow removal from mold
● Attachment point geometry ○ Ensure drop in replacement
Design Overview Critical attachment points
Design Details ● Three step process ○ Plug pattern, constructed with foam or plywood ○ Fiberglass mold ○ Carbon sandwich
Design Details Continued ● Monocoque broken down into three sections ○ Nosecone ○ Hood ○ Body
Design Details: Carbon Sandwich ● A sandwich construction is used in order to greatly improve stiffness of the carbon composite ● Aluminum honeycomb ○ ○
lightweight compressive strength
● Balsa wood hardpoints ● Carbon layers on the inside and outside
Design Analysis Material and ply selection tools ● Autodesk Simulation Composite Design ● Formula Hybrid Structural Equivalency Sheet Final selection ● 8 UD laminae or 4 woven laminae per laminate ○ 4 layers 2x2 Twill 3k Carbon Fiber ● 1 inch core, requirements dependent on Autoclave ○ 3003 Aluminum Honeycomb ¼” cells, 5.2pcf
Design Analysis Solidworks Coupon Analysis â—? 15kN Load
Tsai-Wu FOS 3.59 Minimum
Max Stress 340 KPa Maximum
Ply 3 (45deg) Stress 115 KPa Maximum
Design Analysis Torsional load 15kN at lower front suspension â—? 3.29 minimum FS â—? 11mm maximum displacement
Construction - Plug ● Exact replica of the product is constructed ○ Plywood or foam
● Fiberglass coating ● Primer
Construction - Mold ● Plug is coated in release agent ● Gel coat applied ● Fiberglassed and resin then left to set
Construction - Product ● Mold is coated in a release agent ● Carbon and resin are laid on the inner face ● Vacuum bag seals the entire mold to ensure good contact between the carbon and mold.
Construction - Vacuum Bagging ● ● ●
Nylon peel ply and polyester breather fabric laid over wet carbon Wrap mold in thin bagging film and seal with gum tape Draw vacuum through sealed valve
Objective Analysis ● Low weight achieved ● Compatible with the current systems of the car ● Could be reproduced in 2 days ● Unable to compare stiffness ● Unable to compete in 2014 competition due to deadline
Budget Overview Plug
$180
Mold
$355
Monocoque
$1280.50
Steel
$92.50
Vacuum Supplies
$283
Tools
$560
Miscellaneous
$240
Total
$2991
Testing Results Nondestructive tests only ● 3-Point Bend ● 160 lbs point load ● 0.091 in deflection Weight ● 38 lbs Lack of test coupon evaluation
Issues ● Plug material selection ● Delays due to construction difficulties ● Poor surface finish ● Plasan Carbon Composites
Conclusions ● Use of off site facility ● Different plug construction method ● Prepreg carbon fiber and autoclave
Future Work ● Steel support structures ● Trim flash ● Pinpointing and drilling attachment points ● Hood reconstruction ● Test coupon analysis
Acknowledgments Facilities and Funding
Materials
Questions?