wierd question abot doors

[KnifeEdge_2K1]

as we all know carbon fibre hoods and trunk lids are a good way of lowering weight on a vehicle because they're easily accesible and can be remanufactured using lighter materials easily

now, i don't hear many people doing this with their doors very often. They arnt much more complicated to take off than a hood or trunk lid and I don't know this for a fact but i think they're pretty heavy. wouldn't making the doors outta carbon fibre or something also substantially lower the weight?

the only problem with this as far as I know would be the locking systems and windows, I don't know much about what goes on in the door but i figure the frame itself can't be integral to these systems.

[whiteballz]

i guess it would work...

and if it was, you could just re-create the original shape etc of the inside of the door, so i guess it dosent matter.

[Egg Nog]

I've seen doors done before, but they are exponentially more difficult to fabricate. The locks, handles, windows, and all the associated parts make doors a very complex shape. Moreover, most of the complexities are on the inside, making it hard to properly mould and create. Waaaay harder than a hood or a trunk lid.

[escort mexico]

i has been done, such as on the Apex'i vmax drag car. it does make sense on something like a drag car, where weight is important. what they did was they only had the outer skin of the door (the bit you see from the outside), windows weren't needed, bit of a waste of time if you are going to spend $$$ on reducing weight, so lexan gets screwed onto the door frame. to hold the actual door together they somehow molded the roll cage bars into the door. lots of time and money spent. something tells me that it isn't really worth the money, for anything other than big budget race teams. which is crap, because everyone loves carbon fibre

[cp01ae]

You should also remember that some cars have crash structures built into the doors, these structures also help to give some cars their rigidity, if they lost this, the positive benefits of the weight reduction might be canceled out anyways. Not to mention the loss of safety to the occupants.

[KnifeEdge_2K1]

Originally Posted by cp01ae

You should also remember that some cars have crash structures built into the doors, these structures also help to give some cars their rigidity, if they lost this, the positive benefits of the weight reduction might be canceled out anyways. Not to mention the loss of safety to the occupants.

but cant u duplicate the factory door with a lightweight carbon composite ?
since carbon fibre is stronger than steel wouldnt that increase rigidity and reduce chances of getting hurt in an accident?

[Matra et Alpine]

Originally Posted by KnifeEdge_2K1

but cant u duplicate the factory door with a lightweight carbon composite ?
since carbon fibre is stronger than steel wouldnt that increase rigidity and reduce chances of getting hurt in an accident?

C/F is strong in compression and extension than steel.
C/F is WAY weaker in side/edge impact.
a C/F bar in a dorr would struggle to get the strength of a folded stell component and would be heavy and expensive.

You could possible recover some of the strength by building the dooor as a monocoque, but that woudl leave no room for important things like windows

[Karrmann]

doors just have all those complex parts that are hard to assemble and dissassemble

[Ferrari Tifosi]

Originally Posted by Matra et Alpine

C/F is strong in compression and extension than steel.
C/F is WAY weaker in side/edge impact.
a C/F bar in a dorr would struggle to get the strength of a folded stell component and would be heavy and expensive.

You could possible recover some of the strength by building the dooor as a monocoque, but that woudl leave no room for important things like windows

Way weaker is an understatment, Carbon Fiber's shear strength is horrible, but yes tensile and compression strength's are amazing. Take a carbon fiber and put it in the tensile strength tester and you're going to have to apply 200,000 + psi to break it, however you take a pair of scissors that a five year old owns to it and it is cut easily.

Funny story about this, had a kid in my manufacturing processes class who wrapped a carbon fiber around his finger trying to "break it", idiot. Well the carbon fiber sliced right into his finger, nasty cut. I hope he thinks twice about following through with Mechanical Engineering.

[KnifeEdge_2K1]

Originally Posted by Ferrari Tifosi

Way weaker is an understatment, Carbon Fiber's shear strength is horrible, but yes tensile and compression strength's are amazing. Take a carbon fiber and put it in the tensile strength tester and you're going to have to apply 200,000 + psi to break it, however you take a pair of scissors that a five year old owns to it and it is cut easily.

Funny story about this, had a kid in my manufacturing processes class who wrapped a carbon fiber around his finger trying to "break it", idiot. Well the carbon fiber sliced right into his finger, nasty cut. I hope he thinks twice about following through with Mechanical Engineering.

yeah but when u manufacture something outta carbon fibre dont you cure it with epoxy which hardens it? are you saying you can cut a CF bonnet in half with scissors?

im confused

[KnifeEdge_2K1]

Originally Posted by Matra et Alpine

C/F is strong in compression and extension than steel.
C/F is WAY weaker in side/edge impact.
a C/F bar in a dorr would struggle to get the strength of a folded stell component and would be heavy and expensive.

You could possible recover some of the strength by building the dooor as a monocoque, but that woudl leave no room for important things like windows

what exactly do you mean by comression/extension and side/edge impact

say i had carbon fibre hood or something, what would be compressiopn extension forces and side edge impact forces?

[KnifeEdge_2K1]

http://www.superstreetonline.com/techarticles/54702/
look at pics 17 and 18

would that quallify as side impact? there doesnt seem to be any damage

[Matra et Alpine]

Originally Posted by KnifeEdge_2K1

http://www.superstreetonline.com/techarticles/54702/
look at pics 17 and 18

would that quallify as side impact? there doesnt seem to be any damage

No because that is applying a force which is trying to stretch fibres. That is it's strongest direction and why weabve works on large panels.

I can't find any drawings or pics, but the example everyone has seen is F1 suspension arms. These are designed to take huge cornersing forces as they turn at 6G. The forces from the tyres through the arms to the monocoque are big. But if you stand on one of these arms they shatter.

It's not the side impact of a panel that's the issue, but the side impact on any strengthening sectson you'd have to put in to survive side impact. hence why I'd said it woudl take a monocoque construction as this spreads forces into strech and compression of the monocoque chambers.

In the example in p17, I'd be intersted to see how they got the car on. It would be likely to shatter the sections at the edges of the bonnet where strengthening ribs were added. They would not take the force well as that small section woudl created point forces well in excess of the fiibres shear strength.

[Ferrari Tifosi]

Originally Posted by KnifeEdge_2K1

yeah but when u manufacture something outta carbon fibre dont you cure it with epoxy which hardens it? are you saying you can cut a CF bonnet in half with scissors?

im confused

No you couldn't cut a CF hood in half with scissors. I was talking about the fiber itself, which is where practically all the strength comes from, as the resin is just a hardening material. Composite materials get all their strength from the fibers and hardly any strength is added by the resin.