Re: [Harp-L] Carbon Fiber Reeds, 3D printing, plastic metal adhesion technology...?

[Zombor Kovacs <zrkovacs@xxxxxxxxx>]

Carbon fiber has been present in the consumer market since quite a while, not to mention aerospace. The knowledge and theory is available since many decades. So I would say "everybody" knows how to design carbon fiber composite parts. Designing the material means that you design the structure (ply order, shape, geometry, choose resin and fiber type) according to your loads and this is different for every part although the theory is the same for any part. So if you want to make reeds, you will have to take a closer look at the loads on your reed, put them into a computer and design your part with a suitable engineering software. 
Certainly if you know somebody, who has already made such carbon fiber reeds and can "steal" the exact technology, you will probably have something. But I can tell you, that there are a large number of nuances which will make all the difference and even if you think you know how to do it, you will fail. It is an extremely complicated process especially for the size of the parts which need extreme accuracy. It is true, that we are in the 21st century with supercomputers, nanotechnology and spacecrafts so "don't say it cannot be done". It can be done, but nobody posessing the technology and the ability cares a rats ass about harmonica reeds. They would rather make other stuff like nanomachinery, miniature robotic insects, bionic eyes or ion engines for spacecraft. But not carbon fiber harmonica reeds. They are probably not as important for humankind as the aforementioned things. If they were, we would have very nice CF harmonica reeds in a couple of
 weeks. 


________________________________
 From: "bujohn49@xxxxxxx" <bujohn49@xxxxxxx>
To: zrkovacs@xxxxxxxxx 
Sent: Friday, February 22, 2013 12:41 AM
Subject: Re: [Harp-L] Carbon Fiber Reeds, 3D printing, plastic metal adhesion technology...?
 

As usual, its NOT that important to RE-design the CF material for a reed, But better to investigate WHO has already done similar work and borrow ( STEAL ) from them, I mean - Modify existing nomenclature for a Different product....ej



-----Original Message-----
From: Zombor Kovacs <zrkovacs@xxxxxxxxx>
To: Harp L Harp L <harp-l@xxxxxxxxxx>
Sent: Thu, Feb 21, 2013 2:35 pm
Subject: Re: [Harp-L] Carbon Fiber Reeds, 3D printing, plastic metal adhesion technology...?


Hi Folks,  Reading the discussion about carbon fiber reeds, I feel I could add something 
having spent some time at Zoltek Corporation in one of the world's biggest 
carbon fiber factories as an engineer (I graduated as a materials science 
engineer, but not practicing it just have the basic education).  First of all, I have a piece of carbon-epoxy composite sheet which I intended to 
make reeds of to see how they work. I haven't done it yet, I had more important 
things to do, but seeing the interest I will probably do it anyway and let you 
know in a couple of weeks (I am in a workshop reorganisation process).  Carbon fiber is an interesting material used to create composites. Carbon fibers 
are made of a plastic fiber called PAN (polyacrilonitril) which is gradually 
carbonized in ovens while it is stretched. The molecules in the PAN fiber 
gradually straighten out, everyting burns away, only carbon remains with 
extremely strong covalent carbon-carbon bonds. The inner structure created this 
way gives the fibers an extreme stiffness and a very high tensile strength.
To exploit the extreme stiffness of the fibers it has to be embedded in a resin 
matrix, typically epoxy. As carbon is much lighter than iron (the basic element 
in steel), a carbon fiber has a much lower specific gravity than steel, in 
everyday language it is much lighter. And it is not only lighter, but much 
stiffer. Adding this up, we get a material with extremely high weight to 
stiffness ratio, up to 10 times higher than steel.  Regarding reeds, I don't want to say anything before I have tried it, makes no 
sense to guess. What I can say is that there are different grades of carbon 
fiber, with different tensile strength and modulus values and the resin used for 
the matrix also makes a difference. Carbon fiber only works as a structural or 
spring material infused in a resin matrix, the matrix material and fiber volume 
fraction will (fiber to resin ratio basically) will determine the properties of 
the composite material. A great benefit is corrosion resistance. But because 
carbon fiber is extremely stiff, a reed would need to be made much thinner than 
a copper or brass reed, otherwise the pitch will be too high. If fibers only run 
in lengthwise direction in the reed, the torsional stiffness will probably not 
be very high, so the reed will twist easily. And here is another thing to know. 
The inner structure of a carbon fiber composite can be engineered and it not 
only CAN BE but it IS engineered in industrial applications. This is the whole point. You can 
design the material properties of a composite. This is done by laying plies of 
fiber on top of each other at different angles. So first for example you put a 
layer down in 0 degree angle, and put anotherone on top in 90 degree angle, and 
anotherone in 45 degree angle, or whatever your load on your part is. So in our 
case, we have the problem of torsional stiffness in the reed. What we need to 
do, is run a layer of fibers lengthwise in the reed, a layer crosswise, but we 
need two more layers at a calculated angle (eg +-45 degrees)  which will 
counteract torsional load. This way we can design a reed, which will only flex 
well in one direction but resists flexing in any other directions. We could 
probably design the best reed ever, which would never create dog whistles and 
other undesired noises during an overblow for example. It would only deflect in 
one direction, as it should. Now there are some problems here. As you see, you must design the ply order and 
use the appropriate ply thicknesses to get the right reed stiffness. This itself 
needs a high tech engineering software, but this is not the biggest problem. The 
biggest problem is the size of the reed. How do you make it in such a small 
size? It is extremely difficult if not impossible. You need a mould. Then you 
need to lay those fibers parallel to each other in each ply with a determined 
ply thickness - into the mould. Then you close the mould and infuse the plies 
with resin. For this you need tooling, resin mixing apparatus and finally you 
have to cure the whole thing in an autoclave to get the right composite 
properties. There is no way anybody wants to do this, it is too complicated and 
costs too much.
This is the biggest problem. Otherwise it has great benefits. As I said superior 
corrosion resistance, extreme fatigue resistance the longest lasting reeds could 
be made out of carbon fiber. It is not true, that a carbon fiber composite 
cracks. It only cracks if you have not designed your part with the right ply 
order and not used the right resin. Otherwise it will never crack. So a carbon 
fiber reed in theory could be just as well riveted, or bolted down as bonded. 
Another problem then is tuning. You would need to attach metal weights to the 
end of the reed, which makes it even more complicated (we don't want that to 
fall off any time ever). 
To summarize, it is a nice material but to make a good reed out of CF composite 
is beyond what is worth the effort. I will still try making one using CNC 
machining to cut it out of an already existing carbon composite sheet, but this 
will not be healthy, there will always be some loose fiber on the reed surface 
and the whole reed - because it is machined - will not have the correct 
integrity. Still enough to have a feeling about how it works and sounds though.  Zombor
X-Reed Harmonicas