CC Materials/Manufacturing/Assembly Detailed Design

Ownership

Testing/Validation DRI	Contributors	Project DRI
Ivan Cao (Deactivated)	None	Daphne Lai (Deactivated)

Task Chart

Task	Status (type “/status”)	Notes
Find the main material for the cover	COMPLETED	Catamaran Cover Materials/Manufacture/Assembly Concepting
Research material specifications	COMPLETED	Hand to Renzo by the end of the week
Clean up detailed design research	COMPLETED	Check with Adrian on numbers
Manufacturing research	COMPLETED
Mold research	COMPLETED
Waterproofing	COMPLETED
Finishing	IN PROGRESS	Might not be as important EVERYTHING IS IMPORTANT - DAPHNE
Item list of parts and how they will be manufactured (roughly)	COMPLETED
Main material sourcing and pricing	COMPLETED
Foam molds	COMPLETED
Manufacturing research	IN PROGRESS
Infusion equipment	IN PROGRESS
Manufacturing plan	IN PROGRESS

Assistance Task List (type “/action item”)

Check-in Daphne Lai (Deactivated)
Double check calculations with Adrian

Material Detailing

Material strength of Acrylic (Plexiglas), PETG 3D printed plastics.

[1] Acrylic
Yield Strength: 64.8 - 83.4 MPa (Average value: 75.4 MPa)
Young’s Modulus: 2.76 - 3.30 GPa

Flexural Modulus: 2.96 - 3.30 GPa
Flexural Yield Strength: 98.0 - 125 MPa (Average value: 109 MPa)

[2] PETG
Yield Strength: 28.3 - 58.6 MPa
Young’s Modulus: 1.10 - 20.3 GPa (Average value of 2.65 GPa)

Flexural Modulus: 1.17 - 2.76 GPa
Flexural Yield Strength: 39.2 - 88.9 MPa (Average value of 69.5 MPa)

In short, Plexiglas is a strong enough viable alternative for the side walls of the cover.

Gel-coat
Protective finishing layer for composite surfaces.
Leaves a hard smooth surface good for sticking on adhesive.
Requires sanding and buffing for a smooth surface.
If painting the cover, apply gel-coat first then paint over it.

Source:
[1] http://www.matweb.com/search/datasheet.aspx?bassnum=O1303
[2] http://www.matweb.com/search/datasheet.aspx?matguid=4de1c85bb946406a86c52b688e3810d0

Material Strength of Fiberglass Foam Core Composite.

Assuming quarter inch thickness of all fiberglass (no foam core).
This is to make calculations easier, results might be the same with a foam core or even better.

Fiberglass composite flexural strength- 350Mpa.
Fiberglass board of dimensions 0.7m x 0.5m x 0.00635m.
2 x 70kg humans acting as force.
3 point bend test.

Result stress is 72MPa using formula below.
Stress is less than yield strength.

Which means a quarter inch thickness is more than enough and could be thinner.
Note that results are theoretical, but results are no where close to yield strength.

Deflection at load point (more math):

Foam Sandwiching and Resin

Standard epoxy resin is a good choice for fiberglass.
Has heat resistance of up to 150C. Enough time for occupants to escape vehicle in a thermal runoff situation.

Resins in general melt polystyrene and styrofoam foams so they cannot be used.
Polyurethane foams are a good alternative.

Foam are bought in large thick sheets, they can be cut down into size using hot wire foam cutter.
Composites Canada carries urethane foam which is a good place to buy from.

Summary of materials to buy

Fiberglass - 9oz or similar woven cloth
Resin - Epoxy resin
Foam - Urethane foam

Quantity not determined yet.

All available on compositescanada.com

Math

Manufacturing Detailing

Table of Processes (type “/h4”)

Process Name	Details	Notes
Wet layup	Done by hand Manual layering of fiberglass and resin onto both sides of foam core Minimal equipment and tools required	Most inexpensive option and least amount of setup work required
Infusion	Vacuum bagging creates even pressure on the part Nicer finish and stronger part than wet layup Quite a bit of tools required Requires mold (most likely)	Uses more resin Good for parts of the cover where it bends and curves as the pressure from vacuum bagging keeps them in place

For the current cover design, a mix of both manufacturing processes is viable and is probably the best choice in terms of reducing time spent manufacturing and resources used.

Part Name	Mold and Manufacturing method	Notes
Top cover (Front)	No mold really required Wet layup on a flat surface of glass	Creating a flat piece of the cover on glass provides a really smooth finish that does not need any additional sanding Only one side needs to look nice
Top cover (Rear)	MDF mold Infusion	Shape is pretty curved and arches backwards so MDF mold it is
Inner walls	Wet layup on a flat surface of glass	Not the main bearer of load
Front side walls	Wet layup on a flat surface of glass	Not sure if to do wet layup or infusion for the added strength because the side walls would need to support the panel on top resting on it
Rear side walls	MDF mold Vacuum bagging infusion	CAD model for the wall seems too complicated to create a mold manually
Rubber seal	Hand cut with box cutter and a template for the exact shape Laser cutting to shape Send to 3rd party to manufacture	Few options available

Waterproofing

Gasket for battery cover would be stamped out or cut out from a flat sheet of rubber to match the outline of where the cover would sit on the edges of the walls.
Neoprene is what is typically used for gaskets (synthetic rubber).

Gaskets could be manufactured by using die cutting, water-jet cutting, and laser-jet cutting.
Manufacturing could be potentially done in-house with a large enough laser cutter and a large sheet of rubber, or could potentially be made using a small blade slicing the rubber to the CADed shape.

For the seal to be effective, it should be one continuous piece that covers all openings and shall be compressed against the surface of the resting site and the cover so that small air gaps could be filled to prevent potential water from leaking.

Assembly Detailing

Fiberglass/Foam core/Resin cost

Total surface area: 5.19m^2
Widest part of cover: 0.7112m
Required area of cloth: 23m^2 (2 layers each side plus 10% for headroom)

Would need to order 26 yards
Priced at $11.55 per yard
Approx price: $300 (before applicable taxes and discounts)
Link: https://shop.compositescanada.com/#/product/FJ09-7725-38-LY

Foam:
One sheet of foam cut into 4 thinner sheets covers 5.946m^2

Would need to order 1 sheet
Priced at $42.6 per sheet
Approx price: $42.60 (before applicable taxes and discounts)
Link: https://shop.compositescanada.com/#/product/U720-100-48

Resin:
Ratio by weight is 2.5:1 resin to fiberglass
Fiberglass is sold by weight per square yard
Total area 20.76m^2 or 24.83 yard squared
Total weight in cloth: 24.83*8.8oz = 218.504oz. Around 6.2kg
Would require 15.5kg (34.17lb) of mixed resin.

Foam for mold

Solid insulation foams from local hardware stores are good mold making material.
Can glue multiple sheets together to increase thickness for desired mold shape.

Volume per sheet: 2304 sq. in
Front right and left wall: 182.22 sq. in
Rear right and left wall: 289.66 sq. in
Front lid: 790.32 sq. in
Rear lid: 2521.2 sq. in
Total mold volume: 4255.27 sq. in
Requires 2 sheets: $40 total