SpecBC wrote:
I have considered doing a semi-monocoque chassis as well, but I think my concern comes from not having an autoclave to cure the chassis in(not to mention my total lack of experience with CF lol).
I think I could make a tub mold but I am still not clear on how these monocoque chassis are made, as in do they use honeycomb panels for the entire car or is it mostly just multiple layers of CF fabric? I feel like on some of the cars that have the suspension subframes basically just made out of CF, I don't get how they make that hollow portion and cure it all on the back/inside of the part. Maybe that is where the pre-preg and autoclave come into play.
I was trying to think of a way to vacuum form a tub but I still don't know the answers to the above questions so that would be difficult. Obviously a steel space frame is still the easiest and cheapest by far but it would be fun to do a CF tub
Do you know any of the answers to these questions RebecaLynn?
Good luck with your project, sounds pretty awesome.
Ben
If I may address this a bit, I've worked with composites a fair amount, in design and manufacturing. Mostly FSAE with some school and personal projects, and some mold design and production (carbon/FG cases) for an old job I had.
An autoclave isn't necessary (the resin will set on its own at room temp with or without air/light exposure), but a vacuum bag setup with absorbent cloth is pretty much a must for decent pieces. It's not too bad to work with, but prepreg is sooo much easier and more precise to cut and lay, but it requires an autoclave (plus vacuum bag) to cure, which gives you a lot of time to lay up compared to dry mat. Fiberglass is easier to work with and more tolerant of manhandling during lay up (due to CF's wide weave and structural properties), but once get the hang of which ways it can bend and be shaped over/around/into molds or forms using the weave and apply the vacuum bag well, the end quality starts rising quickly.
There are a variety of ways of making monocoque chassis, from laying individual layers of dry mat soaked with resin, to premade honeycomb sandwich panels which you can cut, bend and bond, to additions of kevlar layers or aluminium or nomex (among others) honeycomb between layers of varying thicknesses, cut and laid around or inside a mold, which is how F1 monocoques are constructed.
Tubs can be made from pretty much anything that will hold its shape during curing, release the part easily, and allow a vacuum bag to reach the entire surface not exposed to the mold. Milled billets are great for smaller parts, but I've used everything from coated MDF, fibreglass (usually a negative mold off of the original/concept with wood bracing), machined alum and steel, though I'm sure there are many more ways to skin this proverbial cat.