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Why not completely replace fiberglass with carbon?

 
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andrey



Joined: 08 Dec 2012
Posts: 3

PostPosted: Wed Mar 14, 2018 3:11 am    Post subject: Why not completely replace fiberglass with carbon? Reply with quote

As far as I understood, carbon young modulus is 3 times greater, than fiberglass. So 3 times less is needed, to get the same stiffness. Tension strength overpowers for typical ski tension forces for both materials.

So, what are reasons (except price) to use fiberglass?


Last edited by andrey on Sun Mar 18, 2018 7:56 pm; edited 1 time in total
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gav wa



Joined: 18 Feb 2014
Posts: 359
Location: Perth

PostPosted: Wed Mar 14, 2018 4:12 am    Post subject: Reply with quote

Get out and ride a full carbon ski or snowboard. Totally different ride than the same with glass.
It would be fun to ride a full carbon powder board, but i doubt i would prefer it over a glass board.
Super light isn't always better too. Overly light boards don't handle chopped up snow as well as boards with a bit of umph. An F1 car will come dead last in an offroad race.
I have a nice thick, heavy freeride board that has no carbon and on a steep as icy chute i wouldn't choose anything else. Whatever is in front of you and no matter how steep the line you can straight line this thing through anything.

Slalom race gear probably works killer with full carbon though.
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vinman



Joined: 09 Nov 2007
Posts: 1311
Location: The tin foil isle

PostPosted: Sat Mar 17, 2018 12:03 pm    Post subject: Reply with quote

I really like a mix of glass and carbon. Glass for that smoother damp ride and a little carbon for just a little added pop.
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24Dave



Joined: 03 Oct 2011
Posts: 99

PostPosted: Fri Mar 23, 2018 7:45 am    Post subject: Reply with quote

I've made heaps of powder boards in all carbon, but usually with stiff cores and tons of rocker. I love them. But I pick my days here in Utah, pretty much just riding fantastic backcountry conditions.

On a normal profile core one problem that you may encounter is compressive failure of carbon on the deck side. To have the equivalent stiffness of a glass board, you use much thinner carbon and it has less compressive strength than a thick layer of E glass. A veneer layer or aramid or Innegra layer over the carbon helps a lot, but lessens the weight advantage. I'm not saying don't try it.

Also Gav is right on with the way an E glass board will flex deep and absorb shocks from rougher hard snow and the stiffer snappy carbon board-if it really is all carbon it will usually just separate you from the snow a lot more and send a lot more shock to your feet. I have ridden some full carbon splitboards on groomers this year coming and going from bc runs and they carve great on smooth groomers, but really disconnect in the chop.
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24Dave



Joined: 03 Oct 2011
Posts: 99

PostPosted: Fri Mar 23, 2018 7:59 am    Post subject: Reply with quote

I think an interesting all conditions upgrade to the 19 or 21 ounce triax might be like a layer of 4.7 ounce HS (high strength, not high modulus) Textreme carbon at 45/45 or 0/90 next to the core and 6 ounce unidirectional S glass or basalt lengthwise outside of that. Still might explode, but that's part of the fun right?
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SleepingAwake



Joined: 11 Oct 2010
Posts: 123

PostPosted: Fri Mar 23, 2018 9:25 am    Post subject: Re: Why not completely replace fiberglass with carbon? Reply with quote

andrey wrote:
As far as I understood, carbon young modulus is 3 times greater, than fiberglass. So 3 times less is needed, to get the same stiffness. Tension strength overpowers for typical ski tension forces for both materials.

So, what are reasons (except price) to use fiberglass?


The problem with that is, that a ski fails looong before you actually reach the limit compressive strength of a given fiber. The laminate fails usually in buckling, which depends amongst other factors on the thickness of the laminate (the bending stiffness of the laminate).

Further more - you would need even less than a third of the weight of carbon for the same stiffness. the modulus is three times higher, but the density is lower so at the same weight a carbon laminate ends up thicker than glass (this is why you need more resin for a carbon or flax laminate compared to glass to get the same volume fraction).

But because the laminate ends up being so thin, the strength of the ski will be lower. To compensate you have to add more carbon and reduce the core thickness. this worsk as the stiffness of the ski is proportional to something between the core thickness squared and core thickness cubed, while the strength is linearly depended to the core thickness.

In the end the weight saving does not come from a lighter laminate, but from a thinner (=lighter) core. So overall the mechanical design of a carbon ski is much more complex than full glass desig.

And i agree that full carbon just doesn't feel as good. I usually mix carbon, glass and Flax in different orientations to get the best properties out of all the fibers.

I hope this is helpfull. Don't hesitate to ask if it isn't - I'm writing this from an airport and the belgian beers are delicious!

Cheers!
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rswilliams13



Joined: 26 Aug 2011
Posts: 7

PostPosted: Fri Dec 07, 2018 7:36 am    Post subject: Reply with quote

24Dave wrote:

On a normal profile core one problem that you may encounter is compressive failure of carbon on the deck side. To have the equivalent stiffness of a glass board, you use much thinner carbon and it has less compressive strength than a thick layer of E glass. A veneer layer or aramid or Innegra layer over the carbon helps a lot, but lessens the weight advantage. I'm not saying don't try it.


Don't use Kevlar/aramid on the top, it is one of the worst composites under compression, much worse than glass or carbon, it's great under tension though. Basalt is around 20% better than e-glass under compression and tension if you want to experiment with other materials. basalt has great dampening properties too. I've been experimenting with carbon basalt hybrid layups and liking the results.

As others have said, carbon is much stiffer than glass, but really not much stronger and worse elongation properties, I've experimented with some super light full carbon snowboards, and they have basically all broken.

I tried replacing 20 oz triax glass with a full carbon stitched 45/45 biax and uni-directional combo totaling about 8-9 oz/yd and they were much weaker and I didn't like the dampening properties.
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