Comparison of 4130 and 2024 Tubing, Composite Tubes too.

Discussion in 'Tube and Fabric' started by wsimpso1, Nov 4, 2019.

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  1. Nov 11, 2019 #41

    Aerowerx

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    The true test of an experiment is if someone else gets the same results.

    Carry on, Adrians!
     
  2. Nov 19, 2019 #42

    AdrianS

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    Lost rhe latest spreadsheet in a hardware upgrade.
    Will redo with improvements in a week or so, including stiffness.
     
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  3. Nov 20, 2019 #43

    cheapracer

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    If I may make a request, re; "composites", can we do E-Glass as it's far more common than carbon fiber, and E-Glass extruded tube is commonly available too.
     
  4. Nov 20, 2019 #44

    AdrianS

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    The spreadsheet is based around lookups for material properties, so given accurate data it's easy to add new materials.
    However, there are so many variables in composite construction it becomes hard to manage. Weave direction, plies, resin properties...I'm slowly bookmarking sites that give actual technical data on their CF tubes, not just UTS.
    When I get back from next weekend away, I'll post what data I need, and the HBA squirrels can find the specs.
    I'm going to add wood, too - why not?

    Hey kids - here's how to re-design your kit airplane in simple, affordable poly pipe.
     
  5. Nov 20, 2019 #45

    cheapracer

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    Ok, I'll try to get you some tube specs tomorrow.

    This FRP i-beam might be helpful to Billski as he may have experience running the numbers on his wing i-beam ..

    Thought it might be helpful to cross reference findings with similar common steel beams.

    200mm x 100mm by 8mm
    For Ludites: 8" x 4" x 5/16"

    The beam shown is of course not representative of that size ...



    billski i-beam 2.jpg Billski i-beam 200 x 100 x 8mm.jpg
     
  6. Nov 20, 2019 #46

    AdrianS

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    I'll have to redesign things a bit to handle the extra dimension.

    In the meantime my 'puter is busy transcoding 50 year old films to a DVD edit.
     
  7. Nov 20, 2019 #47

    cheapracer

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    German girls with the very dark sunglasses?
     
  8. Nov 20, 2019 #48

    AdrianS

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    Sorry. Family 8mm starting in 1963.
    There are cool sunglasses in some shots.
     
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  9. Nov 20, 2019 #49

    wanttobuild

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    Glass is good. More flexible.
    The question is, who is gonna ask the question we all have? LoL
    The 12ft x 3/4" x 51/2" spruce spar.
     
  10. Nov 20, 2019 #50

    cheapracer

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    What, you think I'm looking at them to build a bridge?

    Problem with 'glass is fantastically strong in tension, much, weaker in compression. You really have to know what you are doing to size one up for a spar, and that ain't me, not many out there who can.
     
  11. Nov 20, 2019 #51

    wanttobuild

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    Carbon for the spar
     
  12. Nov 20, 2019 #52

    cheapracer

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    No thanks, I can do titanium for the same price, far more versatile and robust too.
     
  13. Nov 21, 2019 #53

    aeromomentum

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    Keep in mind that the critical failure point for most low diameter/length tube structures is buckling. So modulus of elasticity and density are the critical things to look at. In general aluminum does better than E-glass in this application. Carbon is over twice as good as titanium. Titanium is about 30% better than Aluminum. Aluminum does better than steel. But shape, size and alloy matters. For example an extruded aluminum tube can have fluting or ribs (internal or external) and then it can be better than smooth wall carbon.
     
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  14. Nov 21, 2019 #54

    cheapracer

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    All true ... and then there's the reality of it all, well my reality anyway, rather than the facts on paper.

    In 24 hours I could have a Titanium spar designed and made. In 3 to 5 days I could do the same in 6061T6, maybe, or maybe 24 hours if I could find a 6mm sheet locally.

    Fiberglass extruded beam or tube, as above 3 to 5 days delivery.

    6061 Extrusion, 2 to 4 weeks depending on how busy the factory is, and if they have 6061 ingots to hand.

    Hand laid E-glass epoxy a week or 2, but I would need an expert to design it for me, as for Carbon Fiber, I wouldn't know where to start!

    As is often cited around the forum, what's best is not only what materials you know, but also what you can get you hands on, and must include what processes you have available to you locally.

    Of course cost is also a factor, Ti is still hideously expensive, about $25 per Kg, or $11 per Lb. a set of spars costs me way more than the entire aluminium sheeting for the plane.
     
  15. Nov 21, 2019 #55

    wanttobuild

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    I think there is a lot of interest in this subject.
    I am surprised to see Aeromomentum chime in.
    I am watching his site for the AM10 mount info.
    Maybe a lot of non welders can resurrect some old rag and tube designs.
    Ben
     
  16. Dec 1, 2019 #56

    wsimpso1

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    Hey, I have not forgotten about this, just had a bunch of other things that had higher priority, like dealing with the leaves, finance prep for taxes, making airplane parts, getting the ADS-B In and Out working on the wife's airplane, you get the idea.

    It is time to move on to composite tubes. This stuff can get fussy. What we did for tubes in compression gets only a little hairier because you have to use the E11 for the laminate angle of the cloth used to make the tube wall. In tubes that are table rolled from BID or BIAX cloth, the fibers are all at + and -45 degrees. But you can use UNI cloth and put it at different angles to suit your loading. Just a for-instance of running the UNI cloth at + and - 30 degrees to the long axis, which works out to 90% of your cloth at +/- 30 while 10% of your fibers are at +/- 60 degrees from the long axis. Yes, there is payoff for going from +/-45 to smaller angles relative to the long axis of the tube - the tube gets stiffer in the long direction, which means it will not need as thick a wall to support column loading that way. We have transforms to get the stiffnesses for cloth made this way, we can set the ID of the tube, and add plies until it passes at the same loads as the 1 x 035 steel tube did. Now that right there made your head hurt, you just wait.

    We are also doing tension, which gets down to tensile strength of an off axis composite. To maximize this we want as much of our fibers the long way of the tube as we can stand, just like for compression, except that we do not have to worry over Euler and Johnson, tensile strength sets the game.

    Then we have torsion. Best fiber orientation for torsion is +/- 45 degrees, unless you want it soft or weak in torsion...

    Then we have bending and we go back to strength the long way in the part, both in tension and in compression, pretty much like we did for metal tubes, except we have to find that strength for our fiber orientation and mix.

    In all of these, we can do some siplifying if ALL of the fibers have the same set of orientation, +/- 30 degrees or +/- 45. Mix up the fiber directions, like with table rolled TRIAX or some UNI cloth used the long way, and it gets more complicated. Also if you mix loadings, like torsion and bending at the same time, it also gets more complicated. We have to compute the [ABBD] stiffness matrix for each lamina, then add the peices together to get the whole section's [ABBD] matrix, figure out the {FM} load vector, then solve for {ek}strain vector and then decompose through the lamina to get strains then check for failure criteria. Lots of stuff ahead of me. I intend to compute the smallest tube ID that can pass at the loads that eh 1 x 035 steel tube can carry, and then iterate the tube ID and thickness until I get the lightest tube that passes. I will not go below about 0.030" wall, and I may use braided tubes... Gotta see how it works out.

    Maybe do all this in the next week, but the homebuilt airplane wants me to make a fuel tank and some heat/ventilation parts too. So we shall see.

    Billski
     
  17. Dec 1, 2019 #57

    AdrianS

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    Great.
    We've had the party, and I'm redoing my isotropic materials spreadsheet.
    That's straightforward, and can be easily extended to any metal. But -
    I've been reading up on composite anaysis, and there are just so many variables, as Bill pointed out.
    Given the formulas, I can build pretty comparison sheets, and even set up an iterative solution seeker, but I'm following bill, not leading :).
     

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