Carbonfiber skids

[Zombieitch]

I have been considering fabricating a set of skid plates out of carbon fiber. I have got a relatively high working knowledge with creating stronger than steel laminates. I'm wondering what the thoughts impressions your thoughts are. I'm not talking about the looks cool but that's it over priced junk either. Mostly because I can.

 

[Prime]

I am intrigued by this and I would like to see a strength comparison vs the same or similar thickness of plate steel.

 

[Roadwarrior]

Are you not worried about a gash wrecking the skid? I guess when I look at steel skids I see sharp points as not as bad because the steel (with its strength) just causes a small "scar" or gash.. however I would be afraid of carbon fiber wanting to shred when gashed..

Then again I am not too familiar with the actual product so.. I could be wrong.

 

[Slasa]

I'm with Prime. I would like to see how this turns out.

 

[Zombieitch]

Carbon fiber verses Steel strength.

(Material/Density(lb/cu in)/Tensile Strength(psi) Modulus10^6psi/Sp.Modulus
Steel / .280 / 160,000 / 22.0 / 78 )

TENSILE STRENGTH /DENSITY /SP. STRENGTH
CARBON FIBRE 3.50 / 1.75 / 2.00
STEEL 1.30 / 7.90 / 0.17

Carbon fibre has a tensile strength almost 3 times greater than that of steel, yet is 4.5 times less dense.

I'm very much in the early stages of figuring this up, I need to take measurements, calculate the laminate thickness, so on. Basically to keep cost at an acceptable level, I don't want to exceed the strength of the frame the skid plate would be mounted on.


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[Silver dude]

What about abrasion resistance?

Seems like a good idea nice and light.

 

[Prime]

What about abrasion resistance?

Seems like a good idea nice and light.

This would be crucial. Sometimes you have to just drag across something.

 

[Silver dude]

Or impact resistance.

 

[Roadwarrior]

What about abrasion resistance?

Seems like a good idea nice and light.

This. This is what I was talking about..

 

[ThePlasticOne]

I would highly advise against CF skids.

Sure, tensile strength seems high, but how brittle would the skids be? If I dropped down on a sharp rock with a mild steel skid, I end up with a dent. If I did the same with a CF skid, it could crack or even shatter. Skids have to be able to withstand a drop onto a sharp object; the more brittle they are, the less protection they can actually offer. This is why stainless skids aren't the norm - stainless is more brittle than mild.

CF skids do exist, but they're mainly for bikes, which don't see the same kinds of impacts and forces that an offroad truck does.

Watch this fellow put bullets into (and a slug straight through) a significantly thick piece of CF: http://www.youtube.com/watch?v=qoP0iPzupKc

An equivalent piece of steel would just have a little ding. A 9mm rounds imparts between 300 and 500 ft-lbs of force - an SUV can exert thousands of pounds of force, and we know that 3/16" mild steel skids can take the impact (albeit with likely deformation). I don't think an equivalent piece of CF could handle it.

 

[xterror04]

This would be interesting, I would think you would need some sort of thick epoxy coating on them to help slide over objects, I just don't see them lasting long though, the weight savings would be awesome over steel, but I jut don't see them lasting to abuse

 

[Zombieitch]

My two primary concern points have been been brought up. Abrasion and, impact resistance. Both things are rather obvious issues to me.

The engineering sample in the video, appears to to be a nonimpact load baring sample. Many more options exist today than a basic woven cloth.

I'm looking at more of a hybrid laminate honestly using carbon fiber for its strength properties and Twintex for cost reduction and, impact resistance.

Twintex ballistic cloth (also known as Tegris ballistic cloth) should ease impact concerns. This stuff is used to stop IAD's!

For visual appeal I'm thinking of using a hybrid carbon fiber Kevlar hybrid like this:

More later





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[DC xterra]

very interesting, i would love to loose the skid weight. im following this one

 

[Pro-2X]

While trying to not seem like a naysayer, the IED thing is more like a one and done kinda thing and rocks hit over and over. I am definitely not trying to stymie creativity, but I would test it in a manner that wouldn't jeopardize your truck if it fails. Potato gun maybe...:kewl:

 

[NMTerras]

I don't think the shattering of a CF skid plate would necessarily cause damage to the vehicle, in fact the force may well be dispersed with the reaction. however, and I think this has been brought up, you need something which takes a hit and keeps on protecting...unless you want to install new skids every time you get a good pop on one...

 

[rokdaddy]

Carbon fiber verses Steel strength.

(Material/Density(lb/cu in)/Tensile Strength(psi) Modulus10^6psi/Sp.Modulus
Steel / .280 / 160,000 / 22.0 / 78 )

TENSILE STRENGTH /DENSITY /SP. STRENGTH
CARBON FIBRE 3.50 / 1.75 / 2.00
STEEL 1.30 / 7.90 / 0.17

Carbon fibre has a tensile strength almost 3 times greater than that of steel, yet is 4.5 times less dense.

I'm very much in the early stages of figuring this up, I need to take measurements, calculate the laminate thickness, so on. Basically to keep cost at an acceptable level, I don't want to exceed the strength of the frame the skid plate would be mounted on.


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Those tensile specs are sorta useless for most skid plate designs unless you figure out some way to firmly secure the material so that it distributes tensile loading across a large area (i.e. bar clamping). Simple clearance holes with screws/bolts won't work; the forces will usually rip out the holes long before the advertised yield point. There are ways to mold fastener inserts into the layup but it takes careful planning and considerable skill to set up.

Also, there are plenty of fiber reinforced composites that have the toughness (impact resistance) and stiffness that you will need but none that I've worked with (in the aerospace industry) have the hardness needed to prevent gouging on rocks. Once you get a scratch that's deep enough to damage the fiber reinforcement, those high tensile values are reduced to nearly zero.

The idea may work well for a sand rail but for rocks, you will need some serious abrasion protection outside of the composite layers.


-Rok

 

[Pro-2X]

Those tensile specs are sorta useless for most skid plate designs unless you figure out some way to firmly secure the material so that it distributes tensile loading across a large area (i.e. bar clamping). Simple clearance holes with screws/bolts won't work; the forces will usually rip out the holes long before the advertised yield point. There are ways to mold fastener inserts into the layup but it takes careful planning and considerable skill to set up.

Also, there are plenty of fiber reinforced composites that have the toughness (impact resistance) and stiffness that you will need but none that I've worked with (in the aerospace industry) have the hardness needed to prevent gouging on rocks. Once you get a scratch that's deep enough to damage the fiber reinforcement, those high tensile values are reduced to nearly zero.

The idea may work well for a sand rail but for rocks, you will need some serious abrasion protection outside of the composite layers.


-Rok

That is probably the best statement you could make.

 

[NMTerras]

none that I've worked with (in the aerospace industry)

awesome name drop!

 

[rokdaddy]

Ha! That's funny. I didn't mean it that way... I was just describing the applications that I've worked with. Different industries use different composites and use different reinforcement fabric layups; I'm sure that there are a bunch of matrix, reinforcement and layup variations out there that I've never heard of.

-Rok

 

[NMTerras]

Haha - here's a less technical perspective: From my years in bicycle racing (yes, it was a long time ago), nothing matched a chromoly (steel frame) for responsiveness, i.e. rebound from application of force. When you really put the hammer down on the pedals, i.e. sprinting, you never get the response from aluminum or carbon fiber you get from good old-fashioned steel - give and "snap-back." The materials that are stronger and lighter necessarily give something up in resiliency/elasticity. There is less or no "give," and when you reach a giving point it does not bend, it breaks. I think that translates into the technical explanation rok and others have given - skid plates give, and sometimes bend, but don't break, and in so doing protect what's under them.
So...the question is, under the limitations as described above (attachment points, strength across surface area, abrasion resistance, etc.) is there a composite out there you can bounce and drag across rocks with a few thousand or more pounds on top of it that won't snap or shatter?

Lots o' money to the one who can produce a skidplate behind a "yes"

 

[Acasper708]

I didn't read the hole thing but this was brought up on TNX a while back. I would say it would be a great idea. But start with a hardened alloy aluminum for a outer skin, say 1/8" thick? Then reinforced with carbon fiber layers on the inside for strength!

 

[granitex]

Stick with steel, it is cheaper to work with, it works even after you beat the crap out of it, and is as dependable as gravity. Out of all of the materials that you could think of, they have all been used at some point in time, and they all come back to steel.

I have a good friend that has been a rock crawler for years he and his competators have used just about anything and everything but always comes back to steel.

There are ways to lighten them with dimple dies and internal gussets with thinner plate, but steel is still the best material choice.

CF is a better choice for hoods, and other panels.

 

[Zombieitch]

This thread grew faster than I expected this morning when I started it..

First and, foremost I am in the aerospace industry. For the last 15 years I have been involved with complex composite structures, consisting of flight control surfaces, complex assemblies, propulsion systems, among a few all using composite laminates of a wide verity.

Realistically a 0.10" thick composite laminate using CF or, CF with Kevlar will well surpass the stock skid plates from Nissan. Asper proposed a rather good idea utilizing a thin aluminum plate bonded with the laminate would completely protect the laminate from abrasion and, even impact issues.

This article from 2007 supports the general idea.

http://www.tgdaily.com/trendwatch/3...posite-stronger-and-lighter-than-carbon-fiber

Seeing as we love our guns :smile: in this video the materiel used is one I was considering adding to the laminate.

[video=youtube_share;4NdrcJux7LQ]http://youtu.be/4NdrcJux7LQ[/video]

The thread over at TNX was about reducing weight, I among a few others mentioned carbon fiber (CF) laminates at the time but put no real thought into it past that. In this case a lighter skid would be one result, the primary one would be to create something with insane strength properties all around. If I recall correctly the OP on that thread was planning on using an aluminum and, honey comb core laminate. Problem with that idea is, as the aluminum skins take hits the honey comb core begins to crush. Once the core crushes the only strength provided would be from what is typically a 0.05" thick soft aluminum sheet.

Things like carbonfiber hoods are normally a single layer of CF with Kevlar bonded to black fiberglass matting, I suspect the same is true with the skid plates used on dirt bikes. Kevlar will accept color where CF will not.

Much more homework to do and, some awesume ideas to digest.

 

[Macland]

I'm assuming price point on these would be astronomical?

 

[rokdaddy]

Heya Zombie,

Very cool to see that we work in the same industry. It's fun work that has it's drawbacks but I wouldn't trade it for the world.

I hope my aerospace reference didn't seem presumptuous... I really didn't mean it that way. I meant to explain that my composites experience is LIMITED to aerospace applications. There are plenty of other industries that develop CF formulas that are much more applicible to a skid plate discussion.

I responded because materials science is a passion of mine... but I have to admit that I am no expert.

I watched your video and see where you are coming from, but the others that have responded in this thread have equally strong points. it all boils down to three mechanical properties:

Toughness (impact resistance): http://en.wikipedia.org/wiki/Toughness
Stiffness (related to modulus of elasticity): http://en.wikipedia.org/wiki/Stiffness
Hardness (abrasion resistance): http://en.wikipedia.org/wiki/Hardness

All of the CF formulas that I've seen have great toughness and stiffness characteristics, but they lack in hardness.

You're right; Acasper is headed in the right direction, but aluminum lacks the hardness needed to hold up to rocks. A better material that comes to mind is .032" hardened spring steel. It would be difficult to find an effective way to bond it to the composite while allowing the two materials to deform together as one.

It's easy to be taken aback by videos like the one that you posted but if you were to drag a sharp rock across those CF armor pieces with a 5000 lb force, it would compromise the fibers and those 50 cal bullets would fly right through as if it was made with paper. That type of armor is made from a delicate balance of material properties that simply won't hold up to other types of abuse.

Lastly, you cant ignore the fact that the CF in those videos is 1.25" thick. That's great for ablative, disposable, energy absorbing armor, but not so great for semi-permanently installed armor like off-road skid plates. Also, the weight would be very close to the 3/16" steel found on most commercially available skids.

Again, I hope that I'm not coming across as presumptuous. My tagline under my avatar pic says "socially retarded" for a reason.

I like the discussion that you've presented and the input that everyone else has given; it's all relevant. I also like the determination that you have with this.

I want to say "don't give up on this" but I can tell that you don't need that kind of advice.


-Rok

 

[Zombieitch]

I'm assuming price point on these would be astronomical?

That all depends on what you consider astronomical, some people spend a $500+ for hid retrofitted headlights, $400 per LED bar, $600 and, up for complete cat back systems, thousands to upgrade the suspension, before installing bumpers and tire carriers. Yes the suspension upgrades offer by far more than just added weight carrying ability. I'm not even going to post anything about $$ until after I get the laminate hammered down.

Heya Zombie,

Very cool to see that we work in the same industry. It's fun work that has it's drawbacks but I wouldn't trade it for the world.

I hope my aerospace reference didn't seem presumptuous... I really didn't mean it that way. I meant to explain that my composites experience is LIMITED to aerospace applications. There are plenty of other industries that develop CF formulas that are much more applicible to a skid plate discussion.

I responded because materials science is a passion of mine... but I have to admit that I am no expert.

I watched your video and see where you are coming from, but the others that have responded in this thread have equally strong points. it all boils down to three mechanical properties:

Toughness (impact resistance): http://en.wikipedia.org/wiki/Toughness
Stiffness (related to modulus of elasticity): http://en.wikipedia.org/wiki/Stiffness
Hardness (abrasion resistance): http://en.wikipedia.org/wiki/Hardness

All of the CF formulas that I've seen have great toughness and stiffness characteristics, but they lack in hardness.

You're right; Acasper is headed in the right direction, but aluminum lacks the hardness needed to hold up to rocks. A better material that comes to mind is .032" hardened spring steel. It would be difficult to find an effective way to bond it to the composite while allowing the two materials to deform together as one.

It's easy to be taken aback by videos like the one that you posted but if you were to drag a sharp rock across those CF armor pieces with a 5000 lb force, it would compromise the fibers and those 50 cal bullets would fly right through as if it was made with paper. That type of armor is made from a delicate balance of material properties that simply won't hold up to other types of abuse.

Lastly, you cant ignore the fact that the CF in those videos is 1.25" thick. That's great for ablative, disposable, energy absorbing armor, but not so great for semi-permanently installed armor like off-road skid plates. Also, the weight would be very close to the 3/16" steel found on most commercially available skids.

Again, I hope that I'm not coming across as presumptuous. My tagline under my avatar pic says "socially retarded" for a reason.

I like the discussion that you've presented and the input that everyone else has given; it's all relevant. I also like the determination that you have with this.

I want to say "don't give up on this" but I can tell that you don't need that kind of advice.


-Rok

Your cool man, I was actually glad to see another person with working knowledge on the subject. The laminate in the video I posted is twintex bonded to its self, its a fiberglass polymer. http://fiberglassindustries.com/glasspolyprotechdata.htm its really cool stuff. I was reading a tech data sheet on it in automotive applications using it in conjunction with (CF) to create a highly impact resistance laminate with high strength properties as well. One of the interesting points I noticed was that laminate can be drilled and, tapped to allow threaded fasteners, but gave no data on what the fasteners load rating could be. After a good nights sleep I will try and, find the data sheets for the carbon and, twintex laminates.

 

[Zombieitch]

I had a chance to run some numbers, carbon fiber for total strength and, KEVLAR for impacts. Now to find a resin that doesn't mind heat from the exhaust system. I wasn't able to find the data sheet I was looking at, for the material I was considering. I did contract a vendor about it, to get the strength that made it attractive it requires a heated press.. Not exactly a easy process.

As to pricing, I know what I'm looking at for the raw materials. Approximately $1000, with excess that can be used for other coolness.


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