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For further information about how they validated their design and performed physical testing please refer to chapter 4.
Stanford's
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composites dd
Stanford's team had an extensive use of sandwich panels in their monocoque design. They were able to mount their leading arm, front shock, upper control arm, rear shock brace, trailing arm, steering bell crank, steering column, topshell, canopy linkages. To begin, they created an extensive report on the Tensile Testing of Threaded Bushings in Sandwich Panels in 2017 in order to better understand design choices for load chassis inserts. They determined the maximum loading configurations to guide the design of chassis connections.
They also performed FEA on the key mounting points to determine the loads in the x, y and z directions.
List of non structural materials used with composites:
Foaming Adhesive
Econotac
Cutting Carbon:
Scribe lines should be built into the molds from the mold manufacturer
3-5 extra layers of carbon should be added to places that will be cut to prevent rattling while cutting and make stronger edges.
Vacuum Bagging Tips:
- Vacuum bagging on large molds: put stressreleaving dog ears every 23 ft along the mold in
addition to large dog ears near areas where
more bag will be needed (fairings) - While assembling large vacuum bags, DO NOT STEP ON THE BAG OR LET IT DRAG ON THE FLOOR. This will cause microtears and holes which are really hard to find.
- When joining vacuum bags, do not use an overlap joint use a butt joint so that the vacuum tape can be inspected at each point.
- If you are pulling vacuum on four fairings at a time and you plan to use one pump place the pump so that it is near the center of the string of the four fairings. I.e. don't daisy chain four
fairings and put the pump at the end of the line. Place the pump in the middle. Place the vacuum pump at one end of your large vacuum bag and place the vacuum gauge at the
other end. Sometime vacuum failure willnot propagate to the pump on the vacuum. Hardened carbon can easily pierce AirTech Stretchlon stretchy vacuum bag
Place a fan to blow on the vacuum pump so it does not overheat. - When you have vacuum failures spend a few minutes with the entire team searching for the failure, but then you should send everyone out of the room except for one careful person with
good hearing. Turn off all noise sources in the room so it is silent. Have them pull vacuum on the mold, but then turn off the pump. Have that person search alone for the hissing noise of
vacuum failures. Using a stethoscope may help, but sometimes it is a hinderance. Don't forget that you can have punctures in the vacuum bag in the center of your mold in addition to gaps in
the vacuum tape around the perimeter of your mold. You could even have cracks in your mold itself, but if you didn't realize you had cracks in 10/17/2018 Composites Fundamentals - SSCP
https://sites.google.com/a/stanfordsolarcar.com/sscp/home/sscp-2012-2013/composites/composites-fundamentals-and-planning 8/12 your mold before you laid down carbon you
should just go cry or something.
Mold preparation and Release
- Apply Chemlease 15 in two coats to remove
porosity - Apply 35 coats of Frekote 700NC
Inspect the mold for cracks. If you have already
pulled parts and you noticie cracking have
someone vacuum bag the entire mold to see
how bad the cracks are. If it looks like the cracks
will cause vacuum failure you need to seal the
cracks now before you start laying carbon down.
Also check to see if the cracks get worse when
you heat or cool the molds.
Additional Resources
https://www.fpl.fs.fed.us/documnts/fplr/fplr1574.pdf
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