I can’t argue with the difference the choice of fabric makes but it is logical that the stiffest parts would use a combination of the stiffest fabric, the best design from a stiffness perspective, the right orientation and the stiffest resin.
High modulus fabrics are apparently more brittle but the biggest issue with them for me is finding them to buy. I have only once ever found high modulus twill weave fabric available at any of the suppliers I use. Do you have a source for it in America?
Hi mod fabrics are going to be Unidirectional generally… I do believe that they’re not very good for weaving as the crimps will make them much much weaker. If you were using prepregs, i have a load of high mod stuff around. I’ve never seen the high or ultra high mod in a woven, but surely it must exist if it’s feasible?
You would just use the uni in you layup.
I saw this picutre of a music instrument part, this is what I’d do for more rigidity
take a flat piece an try bending it on it’s side and see how much stiffer it is.
They exist as woven fabrics. I have some that I bought a while ago. I just hardly ever see it available to buy anymore. I believe the seller was liquidating some kind of industrial operation.
High modulus fabrics definitely makes a difference to stiffness and sometimes I prefer to trade some impact resistance for greater rigidity. Carbon fiber is usually many times stronger than it needs to be for my applications but I can always benefit from greater stiffness.
I guess it doesn’t really matter what style of fabric it is because you can always use a more attractive style for the surface layer for most applications. The reason why it matters for me is that drapability is a significant concern for some of my parts.
I have found that using a 4x4 twill is good alternative. Even the standard modulus fabrics produce really stiff parts (much stiffer than most 2x2 twill) and drapes easily over sharp bends. I gave up looking for high modulus fabrics due to limited availability a while ago.
I would find less use for unidirectional high mod fabric because it usually means losing the stiffness to weight benefit as I have to add extra layers.
“I would find less use for unidirectional high mod fabric because it usually means losing the stiffness to weight benefit as I have to add extra layers.”
what do you mean by this? The nice thing about the unidirectional is that it allows you to tailor the fiber direction very precisely. Unidirectional is generally thinner and has much higher fiber volume as well, so it’s also generally lighter and stronger than a part made with fabric. Obviously it’s more time to layup as, for everyone twill ply, you’d need two uni plys to make it equal in directionality. Also as you know, Uni is a bit more difficult to work with.
I’ve also used an 8 harness satin weave cloth once, it was exceptionally rigid. Not sure if it was the fiber itself on that fabric, or the weave. The harness and twill weaves tend to be stronger due to the fact that they have less crimps. The harness fabrics though, are a little more of a pain as they need to be flipped over as they’re laid down to ensure good nesting of the tows.
I mean that uni is great where you want to make parts strong against forces in specific and predictable directions but if you want multi- directional strength you have to add more layers to cover it vs fabrics which have bi-directional strength to start with.
As for the thickness, I have had uni fabric in a variety ranging from fairly thin to fairly thick, like my other fabrics. It’s what you order.
Don’t get me wrong. uni has a place and is great for certain things. It’s just not ideal for what I make usually. I do use it where it’s appropriate.
I am experimenting with carbon nanotube resin this week. If I get the results promised on the tin, I’ll be changing a lot of things. Apparently it increases stiffness by 30% without changing anything else. I am kinda curious what it does if parts are made of 100% carbon nanotube (with resin).
The price of nanotubes has come down so much that I am surprised we haven’t seen more use of it. The hype is that it is stronger and lighter than carbon fiber’s.
Yah I hear you about uni… it’s a pain to produce and often times not as durable as a woven part but, also has it’s strengths. 
I just know for high modulus parts, It’s great because it can be tuned for strength in specific directions. I have a ton of it sitting around and still haven’t put it to use 
Nanotubes are cool. Is this the reason that claims to give like 10-20% better numbers? Nanotubes will be in our future soon, I hope.
Yah it’s stronger but, making it in a useable format for aerospace parts is a bit off. They have some larger production machines and are ramping up to try to make it more available. I also have seen that graphene sheets are now available as well.
Please let us know what you think about the nano tube resin. It sounds like it’s a good deal if it does give much much better properties with no other changes.
Interested in your results with nano tubes. I have a freind in the company I buy my resin from ATL composites. They did extensive testing with nano tubes and didn’t have any outstanding results.
They where supplied to them buy a leading german composite company… The company where very dismissive of ATL’s results from there lab using there nano tubes.
So ATL sent them some of there resin , so they could do there own tests using ATLs resin. And see for them selves.
The fact of the matter was , a very high quality resin is stronger than a crap resin filled with nano tubes.
And adding nano tubes to very high quality resin doesn’t make much of a differance compaired to the cost…added so it not worth doing for a small % increase. Concidering a slightly high post cure temp will add more stiffness / strength.
This is 100% the reason for nano tubes have come massively down in price and are not taking to composite world buy storm.
High quality resins post cured at high temps or pre pregs resins are stronger at this piont in time.
The composite evolution is a wonderful thing , so much is always happening in the industry it’s great to be part of it. No time to be bored 
Tim
I think there is more to it. I would certainly agree that there could be at least a 30% difference in stiffness between parts made with quality resin and parts made with low quality resin. That difference is enough to eat up the benefits of adding nanotubes.
Any test has to be done using the same resin and the same everything else. There are too many other things that effect stiffness to do it any other way.
My findings are limited so far but what I have seen is that the amount of nano tubes you add to each ml of resin makes a huge difference. My guess is that if ATL were not able to achieve any increase in stiffness from using nanotubes, it was most likely because there weren’t enough in the resin.
I find it very easy to imagine that resin makers would be a little stingy with the nanotubes in order to increase profit margins. I bought my nanotubes separately so I can decide how much to add (if any).
It’s the same issue with regular carbon fiber strands. If you add a small handful of cf strands to a gallon of resin, there will be no meaningful stiffness benefit. If you do a 50% resin / 50% cf mix, there would be a huge difference. Similarly, there is going to be a huge difference between adding 1/2 gram of nanotubes to a part the size of a car hood and using 1/2 kg.
To put it into a little more perspective for people who haven’t seen nanotubes in person, they look like a black powder. The premixed nanotube resins I have seen are clear and they advertise that it makes no difference to the aesthetics of the part…
Carbon fiber strong but… if I made a sheet of cf that was too thin to even see, how strong would it be? Even if carbon fiber was 5 times stronger, you could still snap a part easily if it was so thin. Thinking logically, how much stronger than cf would nanotubes have to be to make a 30% increase in stiffness from a layer that is too thin for the human eye to see?
I think that the price of nanotubes have come down mainly due to more efficient manufacturing processes with increased scale. The same reason why carbon fiber has come down in price too.
I totally understand where your coming from , but as I know them personally and money and being stingy didn’t enter the equation at all.
They have a large lab…testing , developing new resins all the time.
They really wanted the nano tubes to work well… Spent months and probably hundreds of tests… Not just a case of throwing a handful of nano’s into a gallon of resin and saying " nope didn’t work"
Very definitive results… As I said… They sent there resin to the german comany so there was no bias at all. And they got very similar results.
They where hopeing they could make a stiffer resin , so they could lower the amount of carbon or resin in racing yatchs and have the same strength…but the results just where not there as yet.
And high quality pre preg resin wins at the moment. Maybe in the future things will change.
Nano tubes sure are amazing little things
Cheers
Tim
To save me a phone call, do you know the price of adtech 820?
I wonder about this thread. I never realized a stiffness difference in the resin. If there was a difference it was always fibers or the VF.
I am not suggesting that your friend is the stingy one. It’s the resin manufacturers that I am suggesting are the stingy ones with the nanotubes.
Even if you used 3 or 4 times as many nanotubes as some of the manufacturers use, I’m not sure it would help. I think they are way off.
I think we need to start looking at nanotube to resin ratios as being similar to the ratios we use for carbon fiber to start realizing those potential benefits. Nanotubes are stronger than cf but they aren’t 50 or 100 times stronger (or anything close)…
410.00 5 gallon kit with slow hardener , you wont regret using the adtech resin, best on the market in my opinion
I just purchased a gallon w/hardener. It was like $135 including shipping.
Soller Composites has it listed on their website.
Not a bad price at all.
Just a warning, you have to heat that AdTech up if your shop is not sweltering. I tried a couple of pumps of resin after the gallon was sitting in my shop at 75 degrees for a few weeks, and it was thick as molasses and milky white.
Manufacturer says that the white color will go away as the epoxy is heated. I was not happy as I don’t have an oven in my shop to heat this stuff up before use.
That milky white tint doesn’t effect the color / clarity of the finished parts. I think part of it is the UV resistance additive. It does look concerning when you first see it though…
One of the things that actually impressed me most about this resin is the quality of the appearance of the finished parts. The color is just perfect. It has none of that amber tint you get with entry level resins. Parts made with the entry level resin from CE look almost like they have UV damage yellowing as soon as they are pulled from the mold when you hold them side by side with Adtech parts.
The other thing I like is how well it wets out the cf fabric. You can saturate the surface layer and it stays on the laminate without any fisheye / pooling issues, or you can squeegee most of it out easily to achieve low resin to fiber ratios. Very easy to use.
The thing I don’t like is how long it takes to set at room temp to the point when I can pull parts from the mold without worrying about warping. It does dry quickly with the fast hardener but it still need a full 7 days to become properly stiff.
I think the cure time is fine for one-off hobby parts given the excellent properties you get from a room temp cure but… I think that post curing in an oven is a must for any sort of production environment. I definitely need to use my molds more than once per week.
I consider it to be a heat cure resin for practical applications. I used some to make my last batch of prepreg and it lasted a good amount of time in my freezer.
It’s good stuff. Not life changing and the improvements aren’t dramatic but it has won a place on my shelf for now.
That milky white tint doesn’t effect the color / clarity of the finished parts. I think part of it is the UV resistance additive. It does look concerning when you first see it though…
One of the things that actually impressed me most about this resin is the quality of the appearance of the finished parts. The color is just perfect. It has none of that amber tint you get with entry level resins. Parts made with the entry level resin from CE look almost like they have UV damage yellowing as soon as they are pulled from the mold when you hold them side by side with Adtech parts.
The other thing I like is how well it wets out the cf fabric. You can saturate the surface layer and it stays on the laminate without any fisheye / pooling issues, or you can squeegee most of it out easily to achieve low resin to fiber ratios. Very easy to use.
The thing I don’t like is how long it takes to set at room temp to the point when I can pull parts from the mold without worrying about warping. It does dry quickly with the fast hardener but it still need a full 7 days to become properly stiff. Resisting temptation to make joke about it being like my grandpa…oops failed…
I think the cure time is fine for one-off hobby parts given the excellent properties you get from a room temp cure but… I think that post curing in an oven is a must for any sort of production environment. I definitely need to use my molds more than once per week.
I consider it to be a heat cure resin for practical applications. I used some to make my last batch of prepreg and it lasted a good amount of time in my freezer.
It’s good stuff. Not life changing and the improvements aren’t dramatic but it has won a place on my shelf for now.[/QUOTE]