DIY Prepreg?

Discussion in 'Composites' started by RSD, Oct 2, 2019.

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  1. Nov 2, 2019 #21

    User27

    User27

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    More trouble than it is worth? For a homebuilt aircraft sized moulding just (gently) use a plastic 'scraper' to spread the resin and fully impregnated, then vac bag. To roll out the resin would need a fair amount of experimentation to get the resin spread evenly and to fully impregnate the cloth.

    Reasonably straight forward to create a cored laminate with a wet layup and vac bag, probably the most cost effective method. It is labour intensive, but a roller system will be pretty expensive.
     
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  2. Nov 2, 2019 #22

    Vigilant1

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    Is it possible that the roller machine is overkill? It would seem possible to do this with a table, then a layer of blotter material, a layer of perforated PE, your layup, another layer of solid PE, and a large hand roller. (You'll get a good arm workout in the bargain). Or, just bag the thing and let the resin out through the perf.
    Using the industrial roller machine the excess resin still has to go somewhere--the only options are out the sides (a mess) and to get pushed along into the to-be-rolled section as it feeds in. There will be a lot of pressure applied and (more importantly) a lot of friction as the goo is forced through the fabric. That pressure and friction will produce heat which might be okay (lowering the viscosity of the resin so it will flow better) but could reduce the cure time so much that it is not practical to then get the wetted fabric onto the plane/part and affixed to it. Only testing and trial/error will tell, but it would seem more straightforward to just put the dry fabric in its final destination, wet it out, then remove the excess epoxy with a vacuum bag and the 14psi of naturally available pressure.
     
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  3. Nov 2, 2019 #23

    Bille Floyd

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    Perhaps if Ya used an airless paint sprayer, then the
    roller , to spread the resin evenly ?

    Here is a question of some importance :
    We all know that adding a reactive diluent to epoxy, in excess
    of 5% , will terminate the molecular weight chains. So what
    the epoxy with reducer was sprayed into the fabric, and the
    reducer was allowed to evaporate, then the wet fibers were
    gone over with a roller ; would that keep the weight chain's
    from terminating ?
    This could be done on a really flat , wet-out table ; before the
    fabric was put on the part, or mold.

    Bille
     
    Last edited: Nov 2, 2019
  4. Nov 2, 2019 #24

    TFF

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    Sounds like such a mess. Unless you could buy some dedicated designed machine, you would need a crew operate and to keep some sort of regular rollers clean. Probably pretty waist full as you have to have plenty of resin ready any time make some. You trying to crank the handle and put it in a mold right away? Like a play dough machine?
     
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  5. Nov 3, 2019 #25

    RSD

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    I've been given some information from someone already using this method that will shorten the learning curve considerably.

    The roller system actually isn't that expensive - its a machine designed to curve sheet metal using rollers.
     
  6. Nov 3, 2019 #26

    RSD

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    Straightaway though you lose the consistency and repeatability using the hand roll method.

    You still end up with a heavier and less strong part this way
    Keeping the excess resin in front of the rollers is the aim to prevent mess

    A lot of the heat/friction will be controlled by the speed of the rolling.

    Do I know if this will work - not 100%
    Do I think that the potnetial gains make giving it a try worthwhile - 100%
     
  7. Nov 3, 2019 #27

    Topaz

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    Indeed, that's what experimental aircraft are all about. The other day, I just finished editing and posted a talk from the Experimental Soaring Association 2019 Western Workshop, on materials and methods testing one of the presenters was doing. It's worth a watch (it's up on the ESA channel on YouTube):


    As for your "roller" technique, who knows? You say you have someone who is using it, so they'd be the person who could guide you. Conventional vacuum-bag layup accomplishes pretty much what you're looking to achieve, without the unknowns, but if you've found a simpler solution, definitely try it out and get back to us. If you can do some quantitative testing to show the fiber/resin ratios you're achieving, I'm sure that'd be appreciated.
     
  8. Nov 3, 2019 #28

    RSD

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    I will take a look at it.

    The other person using it is using it to create their own prepreg, but they said that they can't see any reason why it wouldn't work for what I want to do either. Where I see it being especially useful is for complex shapes that vacuum bagging doesn't necessarily suit. I will certainly let you know how it goes, it might be evolutionary, it might be revolutionary,... or it might be one massive sticky mess!
     
  9. Nov 3, 2019 #29

    User27

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    Sounds like you've got it sorted - let us know how you get on.
     
  10. Nov 3, 2019 #30

    RSD

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    I don't think that I am quite at that stage yet but I think that it has a sufficiently good risk/reward or cost/chance of success to make it worthwhile giving it a go. Will certainly let you all know how it goes.
     

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