Question for any Engineers or Materials Scientists out there

[Flem]

I guess I do not understand what kind of improvement you hope to bring to your design.  You only work with one?  which is it, btw?

Nothing here to understand, I'm not tweaking the design. Hill style is my boy bow crush.
I could be wrong but I only see two methods to increase performance. One is thru design, the other is optimizing material selection and orientation. Most focus on tweaking their design, but since thats not an option for me, I'm a material tweaker.

So I have finally come up with some specs for the hypothetical composite. Don't know if its enough, but here is what I have;

Total volume: 103.2cc
Weight of reinforcement: 189.5g
Specific gravity of resin: 1.1g/cc

Since this composite does not yet exist, I don't have a percentage ratio of fiber to resin.
The carbon tow is 24k, 1.8g/cc and I will use approx. 115.2 metres. Don't know how to calculate that as volume. All usage numbers are estimates.
The other thing that I question is how can the mechanical properties be calculated on a material that is progressively loaded? Seems any equation would only yield a linear answer? Unless I am way off in assuming a bow and it's components are considered elastic materials.

[mmattockx]

I could be wrong but I only see two methods to increase performance. One is thru design, the other is optimizing material selection and orientation. Most focus on tweaking their design, but since thats not an option for me, I'm a material tweaker.

Just a dumb question. Does your self imposed bow design restriction preclude adding reflex and the like, as long as the bow looks/bends like a Hill when braced?

Have you found a limitation in the commercial materials that you are trying to avoid or is this an experiment to see if carbon will offer anything extra?

The other thing that I question is how can the mechanical properties be calculated on a material that is progressively loaded? Seems any equation would only yield a linear answer? Unless I am way off in assuming a bow and it's components are not considered elastic materials.

Material properties seldom change due to the loading. Bow materials are most definitely linear elastic materials.


Mark

[Flem]

"Material properties seldom change due to the loading. Bow materials are most definitely linear elastic materials."

Thats where I disagree. Linear=non yielding, non-linear=yielding.

[mmattockx]

Thats where I disagree. Linear=non yielding, non-linear=yielding.

That's correct. Bow materials don't really yield as such in our application, but wood will take some set on the compression side which is similar to yield.


Mark

[avcase]

Nothing here to understand, I'm not tweaking the design. Hill style is my boy bow crush.
I could be wrong but I only see two methods to increase performance. One is thru design, the other is optimizing material selection and orientation. Most focus on tweaking their design, but since thats not an option for me, I'm a material tweaker.

So I have finally come up with some specs for the hypothetical composite. Don't know if its enough, but here is what I have;

Total volume: 103.2cc
Weight of reinforcement: 189.5g
Specific gravity of resin: 1.1g/cc

Since this composite does not yet exist, I don't have a percentage ratio of fiber to resin.
The carbon tow is 24k, 1.8g/cc and I will use approx. 115.2 metres. Don't know how to calculate that as volume. All usage numbers are estimates.
The other thing that I question is how can the mechanical properties be calculated on a material that is progressively loaded? Seems any equation would only yield a linear answer? Unless I am way off in assuming a bow and it's components are considered elastic materials.

Flem,
What is still needed to calculate an estimate are the specs for the carbon fiber you are using.  There is a wide range of mechanical properties for carbon fiber.  The 24k only states the number of fibers present in your TOW material. The volume of carbon isn’t important. The percentage by weight of carbon and epoxy is important.

You don’t want the materials to operate outside their linear or elastic range. If the materials are yielding during normal use, then the bow is not going to last very long.  I even make an effort not to exceed the linear range for the wood core of the bow.

Are you not able to obtain Gordon’s GC-70-UCL for a backing material?  I recently bought and used this for a back on a longbow design.

Alan

[mmattockx]

Are you not able to obtain Gordon’s GC-70-UCL for a backing material?  I recently bought and used this for a back on a longbow design.

Alan,

A while back you told me that fibreglass stores energy better than carbon does. If that is correct, what do you gain by using carbon in your flight bows? Is this just a weight issue or something else? It's not like we approach the material limits of either in a hand drawn bow.

Hopefully this is just a continuation of OP's desire to try carbon lams as an upgrade and not a hijack...


Mark

[Flem]

I've never seen UCL or even ULZ for retail sale. I would not even know what to expect for cost.
I did do some digging and found the specs for the carbon

T800S R1_04132018.pdf

The only reason I'm obsessed with the volume is because I don't have the resin weight, nor do I have a total weight for the unborn composite. I do know the total volume and the weight of one component.
See my conundrum?

[Mad Max]

Change the subject a little.
mmattockx, what did you do for a living? If I may ask

[avcase]

I've never seen UCL or even ULZ for retail sale. I would not even know what to expect for cost.
I did do some digging and found the specs for the carbon

T800S R1_04132018.pdf

The only reason I'm obsessed with the volume is because I don't have the resin weight, nor do I have a total weight for the unborn composite. I do know the total volume and the weight of one component.
See my conundrum?

I suppose it depends on how you make the laminate. I assume you would lay it up, and then you would need to grind it to a thickness and width. Am I correct?  In this case, you won’t know how much fiber is still present in the same. So I would take the finished sample and precisely measure the thickness, width, length, and mass. Do a deflection test if you can, and then take a propane torch and burn away all the resin until just the carbon fiber remains.  Precisely weigh remaining carbon fiber.  This will give a good idea of the fiber to resin ratio by weight.

Alan

[Flem]

Back to square one or post one. Excuse me while I quote my myself;

"So my question, is there any body here who has access to lab equipment that could be used to get some meaningful numbers? Otherwise its just a subjective exercise. I know a couple of you out there have alluded to a materials background and if you are willing to do some testing, I would be happy to pay shipping and any other associated costs."

Call me greedy, but I am going to want more and diverse data if I am putting in the effort to make and or deconstruct this composite.

[mmattockx]

mmattockx, what did you do for a living? If I may ask

I am a mechanical engineer. Do most of my work in oilfield equipment and structures design/analysis/rating/certification.


Mark

[Mad Max]

 

[Stagmitis]

Flem are you thinking about using your laminate for both back and belly? Sorry if was discussed earier.

[Mad Max]

I suppose it depends on how you make the laminate. I assume you would lay it up, and then you would need to grind it to a thickness and width. Am I correct?  In this case, you won’t know how much fiber is still present in the same. So I would take the finished sample and precisely measure the thickness, width, length, and mass. Do a deflection test if you can, and then take a propane torch and burn away all the resin until just the carbon fiber remains.  Precisely weigh remaining carbon fiber.  This will give a good idea of the fiber to resin ratio by weight.

Alan


sounds like a plan to me

[Flem]

Sound like a toxic fiesta burning all that epoxy. I'd like to know who has done that and how much residue was left on the fiber. That and you still won't have squat for stats for your effort. I'm not doing all that just to fill some numbers in an equation!

Just for the back, I've got something else in mind for the belly.........

[avcase]

Sound like a toxic fiesta burning all that epoxy. I'd like to know who has done that and how much residue was left on the fiber. That and you still won't have squat for stats for your effort. I'm not doing all that just to fill some numbers in an equation!

Just for the back, I've got something else in mind for the belly.........

Flem,
Burning away the resin to inspect and measure the fiber content is a pretty standard inspection procedure.  Just don’t do it inside or in a poorly ventilated area!  The resin burns away leaving clean fibers behind.

Otherwise, I’m running out of ideas for you. If your goal is to compare your layup to the Gordon Composite spec, then you have to test it and measure the mechanical properties.  Companies that manufacture composites and maintain their quality invest a lot of time and resources in this.

There is yet another method, but it involves measuring natural vibration frequencies and it still requires you to precisely measure the length, width, thickness, and mass of the sample.

You can also not worry about it.  Just make carbon laminates as best you can and use them. Don’t worry about how it compares to anything else. Do it by feel. Flex the pieces you make. Destroy a few pieces and observe how they fail. Build bows. Make adjustments to your process and do it again.

Alan

[Shredd]

Flem,

You can also not worry about it.  Just make carbon laminates as best you can and use them. Don’t worry about how it compares to anything else. Do it by feel. Flex the pieces you make. Destroy a few pieces and observe how they fail. Build bows. Make adjustments to your process and do it again.

Alan
[/quote]

 

Great idea on burning off the resin... Never heard of that... Simple but accurate... Thanks for sharing...

[Flem]

Yo guy's I'm not worried about anything, except maybe wasting time. Apparently nobody believes me when I say this is an exercise in curiosity. It would be like me telling some of you not to worry how fast or far your bows shoot, just go out and shoot them and enjoy the experience. Don't waste your time chasing some elusive number. 

And besides, I have had a generous offer to have my composite tested by a University testing lab manager!  Now I'm going to have to get off my a$$ and actually make this material.

[Mad Max]

wasting time?
you got nuffin else to do

[Roy from Pa]

Long as yer having fun Flem, that's all that matters.