Carbon Round Tube Lay-up Design for Beginners

Discussion in 'Materials' started by CloudDiver, Nov 9, 2018.

  1. CloudDiver
    Joined: Jun 2014
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    Location: San Diego

    CloudDiver Senior Member

    I'm interested in making some parts using CNC filament winding, mostly utility kinds of things that aren't subject to the heaviest loads like vertical supports for hard-tops (lightweight ones, lol).

    Eventually I'd like to be able to make spinnaker poles, life-line stanchions, etc; those of course have to be designed with specific loads and forces in mind. I have a machine I can practice on, 3 axis with a 12 ft X axis (not mine, but I am allowed to use it). Right now I'm not planning to make anything just yet, just work with the software to create the filament lay-up and examine the properties, cost, time, etc.

    So I'm looking for some general advice on designing the filament pattern, and generally how to change the pattern to address tension, compression, and twist (torque) accordingly.

    Next year I will have my own machine that is 20 ft overall, will likely have a functional 17 to 18 ft X axis. FYI, my max filament deviation from 0 degrees on the long axis will +/- 5 degrees, (I might be using the wrong terms here), but needless to say I can't do a true uni-directional layer long-ways. That's fine, I'm not making masts (good thing I mentioned that to get it out of the way).

    For my first exercise I'm planning to make a 55 mm tube with a .9 mm wall thickness. This is not boat related, I want to replace some 7075 AL tubes and I want to design a filament wound tube that beats all the properties of 7075 in the same resulting dimension.

    FYI, I'll be vac bagging the tube to get the best compression and resin ratio possible from a wet lay up, then post curing around 150 deg F. In the future, after more experience, I could easily dry wind the filament and infuse the resin, but that just isn't necessary at the moment to save a few grams.
  2. JamesG123
    Joined: Mar 2015
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    Location: Columbus, GA

    JamesG123 Senior Member

    Yeah.. most of that will be proprietary information that anyone who could give you that isn't likely too. BDN is about boat design and has a pretty good brain trust of composite peeps, and some build composite masts, but the engineering and laying up of composite tubing is its own animal. Very few boat builders want/could roll their own with a machine. Its not just not economical to invest in the hardware and also figuring out what you are trying to figure out unless they just happen to have someone with that in their background.

    You'll probably have better luck on some of the composite forums and sites, or the vendors who supply the materials or even machine mfgs. Or if all else fails, trial and error it until you get it dialed in. And then you become the expert with the proprietary info you won't share. lol
  3. JosephT
    Joined: Jun 2009
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    JosephT Senior Member

    The book referenced below is a good one. Analyzing strengths for woven composites can be time consuming as the material densities can vary with composites. You might just want to jump into mechanical testing to validate the strength. Chapter 8 has a section on "Static Mechanical Tests" that may be very useful. To increase the strength of a filament wound structure you can go a few routes:

    -Improved resin system (e.g. high temp with autoclave)
    -Increased material thickness (obvious choice...make it thicker to improve strength)
    -Add an iso-grid as the base layer, which basically adds integrated stiffeners to your cylindrical shapes. This can dramatically increase the strength to weight ratio of any cylinder you spin. It will require a disposable foam mandrel of course (e.g. carve grid into foam mandrel, then spin your filaments over it, compress in clam shell female mold for smooth surface).

    I have seen composite spinnaker poles, booms and masts. I have not yet seen anyone fabricate composite stanchions, but they would seem like a very good idea. Existing metal stanchions bend under load and eventually break. A composite stanchions would be fantastic.

    Good luck!

    rxcomposite and Doug Lord like this.
  4. CloudDiver
    Joined: Jun 2014
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    Location: San Diego

    CloudDiver Senior Member

    Thanks very much! Excellent suggestion...
    JosephT likes this.

  5. rxcomposite
    Joined: Jan 2005
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    Location: Philippines

    rxcomposite Senior Member

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