Carbon Fiber Ramps

General Composites Discussions Composites Talk
#1

So I have a driveway with a steep enough angle where I pull out wood ramps when I take my car out. It’s acceptable but since I’m doing composite work now I’d like something a little easier to move. I know ramps have been done before but I just have a few questions.

  1. How many layers and of what fabric. I’ll place probably my next order with solarcomposites.com since they have some of the best prices around that I’ve seen so check their website out and give me some information if you could.

  2. The ones DDcompound made had what looked like 90degree angles, almost like an upside down U shape as the ramp itself. I know these sides will help stiffen the ramp but are they necessary? Could I just make a flat surface ramp, or rather could I get away with making a flat surface ramp? I am planning to attach some type of rubber on the bottom where the front and back meet the concrete so it’s not to damage the carbon

  3. Would you use a core material? Right now I just have some 3mm lantor soric but I figure with 10 or so layers of carbon on each side that would provide plenty of thickness.

Just some other information. This is to aid a 3000lbs car. They’ll be about 2 feet wide and 4 or 5 feet long. I could make them thinner but that would require me to get out of the car an extra time to align things properly. I’d rather have the extra width to play with.

Let me know your thoughts please. Again I’m no engineer and if I mess this up the amount of carbon and such would be a larger waste than or part I normally do so that’s why I’m asking to begin with.

Thanks in advance and I’ll be sure to post results once I get done.

#2

Make them half the width, and make a mark where to put them. This aleady saves you half the carbon…

The sides on the DD Compound ramps are for stiffening purposes.

Cannot help on the calculation part, it would be very nice to make an educational item out of this.

#3

Herman! Just the guy I wanted to reply, haha.

Well I already had ramps that were half the size originally. Then it was a hassle lining up my car and worrying about if I were to run off or not. Then I made new wooden ones and haven’t had an issue.

I like the fact that I don’t need to keep them perfectly straight and I don’t mind if it costs me 2x the price to get what I need since this is a personal project and won’t be for another month or so until I get time.

The calculation part I guess all I’m asking for is how many layers of what people would recommend.

#4

Maybe I should go with some Uni as well? If you scroll down to the end of this page they have all their stuff listed by the foot.

http://www.fiberglasssupply.com/Product_Catalog/Reinforcements/Carbon_and_Kevlar/carbon_and_kevlar.html

#5

I also have problems with getting one of my cars out of the drive and this would be the perfect solution. I’ll be watching this thread to see what you come up with.

#6

Your drive is so steep, you need ramps to get out of it!??!?!

Is this your house?
http://www.nachi.org/forum/attachments/f16/15761d1194038126-max-driveway-slope-driveway_steep2.jpg

#7

Haha yeah, well not that steep.

So I was just told the 90 degree sides are pretty mandatory.

Anybody know now where I can source quadraxial carbon fiber fabric in the US?

#8

Instead of quadraxial you can use 2 layer of biaxial placed with 45degrees.
I used the quadraxial because I got it very cheap.

#9

I hope those are photo shopped.

#10

Ok cool.

Would you use UNI as well in this case? Or just stick with a lot of layers of biaxial?

#11

Of course I would use uni too, you need it to take the loads.

#12

You will need to cut the forces into their respective components.

Worst case scenario is a wheel of the car in the middle of the ramp. You have general bending forces over the ramp, but also local bending forces in 90 direction. (span 60cm/ 2ft).

You will need to find out the amount of laminates to withstand these forces. The flanges on the side help to keep overall stiffness, and can be designed with lots of UD in the top. The rest of the flange is under heavy shear, so should have +/-45, and the surface, due to its size, could have all the UD used in the top of the flange, but distributed over the area. Actually in steel calculations only 30x the stiffener thickness can be taken into account, so if your flange is 10mm thick, only 300mm of riding surface can be taken into account for stiffness purposes. Split that in half, as the surface is only on one side of the stiffener. The rest of the riding surface sort of “hangs” between the side rails, hence the need for 90 degree fiber.

You could also design differently, not U shaped but H shaped, where the side rails will take all bending forces in length, and the bed just the weight of 1 wheel (plus 1/4 car) where the forces should be distributed to the side rails.

#13

I’m bumping this up because I’m slowly starting to try and piece this project together.

I think essentially it’s going to be an expensive trial and error kind of project. I’m thinking of just going with a flat panel that’s an inch thick.

I’m going to source quad fabric just for ease because if I used biaxial and just twisted it I’ll have a lot of waste left over from cutting.

#14

sduffass-

sounds like a fun and pretty easy project. I buy a lot of product from Solarcomposites and i’ve always been happy with the quality and prices. Regarding the design choices, the flat plank would be a good way to go, but…some ideas to consider:

An easy way to consider what orientation to put your fibers is to envision the ramp was made from squishy foam. If you press in the middle where you car wheel would be…the foam would compress together on the top surface and the bottom surface would stretch out. The fiber part of the composite only adds strength along the direction of stretch (bottom). The epoxy resin has high compressive strength so it contributes to the areas under compression (top).

The larger the distance between the top and bottom surfaces makes for a stiffer beam, or ramp. The center of the ramp doesn’t add much mechanical strength or stiffness. So you should definitely use a core material, but primarily to separate the top and bottom layer of the ramp. You could use Styrofoam or anything…probably like 50mm thick.

Without resorting the the FEA calculation, i’d use a thick foam core, uni on the bottom, and a woven cloth at 0, 30 and 45 deg from the long axis all around. Thickness or number of layers…many.

Good luck!

#15

Interesting project. Subscribed.

#16

After speaking with a few people I’ve decided to add the side flanges back in for stiffness and strength. I’m going to have to get someone to weld some flat pieces of steel for me for the mould. I’m still pricing everything out. It’s an expensive project to say the least with a very minimal reward. We’ll see though.

#17

Why not fold some aluminium sheet? Might be cheaper in the end, and no problem with irregular welds.

#18

I thought about that but I would think aluminum would fold under pressure or the sides would cave in or something. I also just thought about making some out of sheets of plywood and screwing the sides on and then sealing it, sanding down flat, and then caulking the edges. A lot cheaper than paying someone to weld but more work.

#19

There is no pressure or forces if all materials are placed correct without tensions. I folded a 2mm steel sheet for my ramps and used a shafted 15mm core.
Look at the carbon fibre ramps thread, there is everything showm and documented.

#20

What you can do also is making the mould from chipboard or similar, and stick self adhesive teflon to it.

In any case make sure it is airtight