Carbon Fiber Monocoque
for the UVM AERO Team
Zak Codington
Jordan Factor
Tyler Gold
Scott Patterson
Mentor: Dr Michael Cross
Abstract
The University of Vermont Alternative Energy
Racing Organization (AERO) proposed that a
carbon fiber monocoque to be designed for the
Formula-Hybrid competition in 2015. As a
monocoque, the skin alone must support all the
loads experienced while driving. The approach
taken was to use a ‘wet lay’ technique with
aluminum honeycomb sandwich construction to
yield the high strength to weight ratio. The
construction of this project is a huge leap
forward for the advancement of the AERO
team. Due to deadlines and difficulties, this
years monocoque will serve as a proof of
concept for future competitions.
Design
The design of the monocoque was intended to
fit all of the current attachment points on the
current car. On top of that, the manufacturing
process had to be considered since
complicated shapes create difficulties in
construction. Minimal curvature of the panels
allowed for the plugs to be created out of
plywood and foam. Aerodynamics took a
backseat in the design as structural integrity,
dimensional accuracy and manufacturability
were the priorities. Final design can be seen in
figure 1 below.
Figure 1: Final monocoque design
Analysis
Competition structural equivalency sheet (SES)
requirements, Solidworks Simulation, Abaqus,
Autodesk Simulation Composite Design were
used to decide laminate patterns, layout, and
number of layers, and core thickness.
Simulated loading conditions, included front
impact, side impact (seen in figure 2), front
torsion, horizontal bending, and vertical
bending. Based on these simulations and
requirements, 1 inch 3003 aluminum
honeycomb was used for the core with 4 layers
of 3k 2x2 twill carbon fiber laminated with
epoxy resins laminated at 0 or 45 degrees.
Material selection was based primarily on SES
requirements but showed adequate strength in
additional simulation. Aluminum honeycomb
was chosen over Nomex due to budgetary
constraints.
Lk
Figure 3: Rendering of the final monocoque with steel structures
Construction
The construction of the monocoque was
done in three separate sections: the main
body, hood, and nose cone (seen
assembled in figure 3). The nose cone
was built first as a way to perfect the
technique for the main body and hood. For
each section, a pattern was created using
high density foam (nose cone and hood)
or plywood (main body). These patterns
were coated with a layer of fiberglass and
epoxy before being painted with primer.
They were then coated with gel coat and
several more layers of fiberglass,
effectively creating molds from the
patterns. These molds were then coated
with mold sealer and release. The outer
skin of carbon was then laid in and
vacuumed to the mold to remove voids
and insure uniform shape.
The three
steps of the nosecone process can be
seen in figure 4.
Testing
According to rules, each team
entering in the competition must
submit the results of three test
coupons to demonstrate the bending
strength, attachment point strength
and pierce resistance. Due to
unforeseen issues with carbon
supply, the testing consisted of a
three point bend test on the
monocoque with a point load of 160
lbs applied at the location of the
driver. The test yielded a deflection of
0.091 in.
Issues
•  Limited resources due to tight
budget
•  Aggressive time constraints to due
to limited facility use, ESF facility
seen in figure 5
•
Formula-Hybrid structural
equivalency sheet competition
deadlines
Ongoing Work
Figure 4: Progression of nose cone from plug to mold to final product
For the main body and hood, sections of
aluminum honeycomb were cutout and
replaced with balsa wood hardpoints and
then glued to the outer skin. The inner
skin was then laid and vacuumed, creating
an ultra-stiff carbon sandwich
construction.
Due to difficulties experienced during
construction, the monocoque is not
currently competition ready. Prior to
driving the following items must be
addressed:
•
Steel support structures
Locating and drilling attachment
points
•
•
Reconstruction of the hood
•
Test coupon analysis
Acknowledgments
This project was supported by the
Clean Energy Fund, Lee Diamond
and the UVM Environmental Safety
Facility, McLube, and Airtech
Figure 2: Panel displacement bending analysis
Figure 5: At work on the main body mold in the ESF workroom