Thermoplastic Composites... really

Damon · Post by **Damon** » Mon Nov 09, 2009 7:20 pm

Has anyone investigated a thermoplastic composite?

Some pros and cons, as I see them...

pros:
-Possibility for a completely recyclable ski, made from recycled materials
-No volatiles during manufacturing
-Tougher (increased impact strength)
-Cheaper

cons:
-Increased manufacturing complexity - since processing temperatures are the melt temps of the matrix, either the Tm needs to be much lower then UHMW, or you use something like PTFE for base material (which I want to try either way)

discuss?

twizzstyle · Post by **twizzstyle** » Tue Nov 10, 2009 10:55 am

Well you certainly get uber-awesome-aerospace points from me, I think this is an awesome idea!

Your pro of "cheaper" though... cheaper than fiberglass/epoxy wet layup? I have zero experience with thermoplastics so I have no idea, but my gut feeling is the cost would be astronomically higher for materials... no?

Is this in the context of a home-builder? Or pro production?

Damon · Post by **Damon** » Tue Nov 10, 2009 12:08 pm

I was touring the Boeing composites facility down in Frederickson and they started talking about thermoplastic composites for the leading edges... got me thinking.

Cheaper... This depends. If you buy sheets of prepreg, it's not going to be cheaper (yet!) but I'm thinking if you use a commodity thermoplastic, you can get sheets(film actually) of the stuff for super cheap. The fibers are the same - at least according to the limited research I've done. I'm planning on doing some experimentation on creating your own rather than buying prepreg.

For homebuilders, the capability of heating to the melting point of a plastic might be a stretch, but again, this depends on what you use. I'm just concerned you'll have to use a higher temp materials for items you don't want to melt... which usually means more money. Found 8"x120"x.062" (wxlxt) sheet of PTFE for a $120....

jvangelder · Post by **jvangelder** » Tue Nov 10, 2009 7:27 pm

PFTE for a base huh? I toyed with the idea of using it as sidewalls, however i threw that idea out after i played with some .125x1.0 msc length scraps i had from a job at work, i thought it would be way to brittle

If you do try it please post up some results

Damon · Post by **Damon** » Wed Nov 11, 2009 2:09 am

Yep. Funny thing about PTFE is it has to be sintered in the processing of the stuff - so it should hold wax pretty readily. Although with a coefficient of friction as low as it is, it probably won't need wax.

Got another quote, 8"x.062" for $5.50/ft... little more manageable.

hjfast · Post by **hjfast** » Mon Nov 16, 2009 5:30 pm

I love the idea of a recyclable ski but it just isn't really possible. While thermoplastics are recyclable with minor material degradation you have to consider that your epoxy is a thermoset. ( http://en.wikipedia.org/wiki/Thermosetting_polymer for the non-engineering peeps)

Thermosets cure through either heat or chemical processes and can not be re-melted or recycled. A recyclable ski would be great but you would have to approach more than just the composite.

-h

Damon · Post by **Damon** » Mon Nov 16, 2009 9:31 pm

I wouldn't be using an epoxy. The matrix or binder would be a thermoplastic resin, likely polypropylene or polyethylene. Although I do foresee an issue with the composite bonding to the base/topsheet/core.

I'm moving forward with this. I am beginning an experiment to optimize the processing conditions for a thermoplastic composite.

I will be using a 12 oz and 22 oz fiberglass, with films of PP or PE in varying thicknesses. Pressed at various temperatures, pressures, and time. Study should be done in a week.

hjfast · Post by **hjfast** » Tue Nov 17, 2009 12:21 pm

Keep me posted. I would love to see how this works out.

Damon · Post by **Damon** » Sun Nov 22, 2009 9:34 pm

Someone in industry gave me a little rundown to help get me started...

The main difference between working with TP and TS is the viscosity of the resin system, TPs are very viscous by comparison to TS – picture trying to push peanut butter through a screen door mesh; that is the process equivalent of resin film infusion using TPs.

Here is what I would recommend as targets to get you started:

· Fiber Weight Fraction (FWF) = 50%
o you should start with equal parts of fiber and resin by weight
· I would recommend that you document the melt flow temperature with a thermocouple in the small batch ovens in the lab.
· I would start with the laminate heated at the melt flow temperature, and then bracket up in 5-10 degree increments
o You will need a thermocouple on the part, and need to adjust the press temperature set point up to achieve the desired temperature – in most cases, the press will be between 10-50F higher than the part, depending upon how well the press and tool are insulated.
· You need to design your laminate so that the part is seeing 200-500 psi – this is good for range finding in your DOE
o You will need to ensure that pressure is being developed on the part rather than the tooling
o Ensure you use standoff blocks to minimize platen deflection and not damage the press

You will want to evaluate primarily ASTM D2344 short beam shear result, this is a resin dominated test and you will be able to determine laminate quality or lack thereof by data scatter.

Additionally, you will want to perform some qualitative tests, usually micrographs and dye penetrant testing, you might not have access to a stereomicroscope or dyes.

The primary problem you will encounter is dry core bundles, to achieve good ASTM D2344 results, the resin needs to flow through the thickness of the fiberglass rovings. What generally tends to happen is that the resin ends up on the outside of the fiber bundle and does not penetrate fully. If you strip the insulation coating off of a multi strand wire, this is generally what a poorly saturated TP laminate looks like rather than the slide above.

scrach · Post by **scrach** » Sat Dec 05, 2009 12:51 am

something I have thought about too, although I am new to ski building and dont have the skill to try just yet.

I would agree with you that the hardest thing is going to be not melting everything else. The right ballance of materials is key.

For the viscosity issue, you might want to look at a product like "Twintex" (Im using it in my masters). it comes in a commingled fabric of glass and PP in fiber form. This helps with the viscosity issue you industry friend is talking about. If the matrix is woven in to the reinforcement ahead of time it you dont have the issue of penetrating the rovings.

Not something that is easy to try at home. keep us posted

doughboyshredder · Post by **doughboyshredder** » Sat Dec 05, 2009 9:40 pm

200-500 psi !!!!!! Yikes.

Damon · Post by **Damon** » Sun Dec 06, 2009 8:19 pm

Yeah - the pressures he's using definitely take this out of home builders perspective. Although he is making aircraft components, so his fiber/resin ratio and dimensional tolerances are near perfect. A goal of mine is to get this to be something w/ reasonable processing conditions.

As far as the experimentation goes, it's been tough getting a good wetout so far - I need to start finding some of those woven prepregs. I've been using film in varying thickness and the resin will encapsulate the fiber, but they are too viscous to penetrate the weave.

scrach · Post by **scrach** » Mon Dec 07, 2009 7:20 pm

googled "thermoplastic skis" and this came up:

http://www.patentstorm.us/patents/55449 ... ption.html

so someone has done it and even gone so far as to patent it. Its crazy what people will go patent to try an make a buck, how is a material selection an "invention" thats BS. no new material was invented, just the application.

anyway, shows that it is possible. I hope thats encouraging. I didnt read through it, but there might be some hint to help your manufacturing.

cheers

doughboyshredder · Post by **doughboyshredder** » Mon Dec 07, 2009 8:36 pm

looks like K2 has thermoplastic skis and snowboards with any fibers and any cores with any type of process patented.

Patents suck.

Damon · Post by **Damon** » Mon Dec 07, 2009 9:32 pm

haha... nice find.

Looks like I've got a solid 4 years to get the process down.

This doesn't surprise me too much - I believe K2 is trying to incorporate some of these processes into their nordic skis, they gave a presentation to the seattle SAMPE chapter recently about their desire to take the "art" out of ski manufacturing - and I think TP composites was one of the solutions.

Sean - see anything when you were there?

Edit... http://www.wikipatents.com/5544908.html-4 - definitely for nordic. Also it appears it only covers cap construction?

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Thermoplastic Composites... really

Thermoplastic Composites... really