Monocoque Design Info.

[Andy]

I have searched through some of the previous posts on the forum, but did not find exactly what I was look for, so I thought I'd start a new thread to help answer my questions.

I was wondering for those teams that build a CF monocoque, what types of core have you used? Is it all Ali or some Nomex too? Do you use multiple thicknesses to save costs, or are you using several varying thicknesses? I also assume sample panels using the design specs were tested in order to determine the strengths of the makeup? Any interesting procedures for going about these tests?

Lastly, I was wondering how teams integrate the main and front rolls hoops into their tubs since typical CNC aluminum bulkheads are not allowed for these areas? Any pictures that might provide some insight would be greatly appreciated. Sorry for all of the questions and thanks for any responses in advance.

Andy

[jack]

i too, have allways been wondering what teams core there tubs with...so i asked http://fsae.com/groupee_common/emoticons/icon_wink.gif at WWU we have a cut/fold tub with some other stuff, big tubes (no core) and cnc bulk heads with roll structures bolted to the bulkheads. we will most likely continue with a basis of a cut/fold chassis. we use .4" nomex panel cored with aramid. we use this because we have lots of it around. as for other schools, --nobody quote me on any of this-- UW uses aramid core too. i think there core was about .375" thick. they have no aluminum bulkheads, and just bolt up thier roll structures, so does UWA, who core there tub with aluminum--im pretty sure, which is about .75" thick? Kanas core thier tub with aramid and aluminum in the corners if i remember correctly. not sure how thick. i remember asking the NC state guys about thier tub, but cant really remember what they said. didnt talk to an ETS guys. hope that helps.

[James Waltman]

I should clarify some of Jack's rambling. We used premanufactured panels for our tub. They are sandwich structures made of prepreg carbon fiber skins and aramid honeycomb core. Our chassis is a little different than most others.

We did testing of the panels to work out how to attach our safety harness. We did testing of the individual components to pass the safety equivalency. I think that some teams have submitted hand calculations and FEA for the safety equivalency and I really don't think that should be allowed – but I'm not on the committee.

The website has some pictures of the safety harness pull-out testing:here (http://dot.etec.wwu.edu/fsae/viking35_safety_harness_testing.htm)

Some of the other pictures on the website may give you an idea as well.

Now some pictures:
The chassis before assembly:
http://dot.etec.wwu.edu/fsae/James/Web%20Pics/V35%20Tub/All%20chassis%20parts%20before%20assembly%20%231.j pg

Front bulkhead outer view – the panel fits in the slots
http://dot.etec.wwu.edu/fsae/James/Web%20Pics/V35%20Tub/Front%20Bulkhead%20Single%20%231.jpg

Front bulkhead inner view – This is one of the two halves. The halves get bonded together so the inside is hollow with ribs.
http://dot.etec.wwu.edu/fsae/James/Web%20Pics/V35%20Tub/Front%20Bulkhead%20-%20Inner%20reinforcements%20%232.jpg

Front Subsection
http://dot.etec.wwu.edu/fsae/James/Web%20Pics/V35%20Tub/Holding%20up%20the%20front%20chassis%20section.jpg

This is how we tried to pass the safety equivalency the first time – simple clamp. They said we needed to use at least 2 C-clamps.
http://dot.etec.wwu.edu/fsae/James/Web%20Pics/V35%20Tub/DSC01774.JPG

Front Roll bar mount – the final mounting for the front bar. Our tubes are the strongest part of the chassis so that is what the bar ties into
http://dot.etec.wwu.edu/fsae/James/Web%20Pics/V35%20Tub/DSC02227.JPG

Rear Roll Bar
http://dot.etec.wwu.edu/fsae/James/Web%20Pics/V35%20Tub/Rear%20roll%20bar%20%232.JPG

Detail of the rear roll bar mount
http://dot.etec.wwu.edu/fsae/James/Web%20Pics/V35%20Tub/Detail%20of%20rear%20attach.JPG