Very low resin content in laminate

Discussion in 'Materials' started by Cacciatore, Jan 23, 2020.

  1. Cacciatore
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    Cacciatore Naval Architect and Marine Engineer

    Hi Guys , what could be the issues about the use of very low content of resin in a laminate stack using Fiberglass or Fibercarbon ? I am talking about 25-30 % in mass of resin content for building hull.
    I know that I increase a lot the mechanical properties of laminate but what are there any problems of delamination or fragility ?
  2. TANSL
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    TANSL Senior Member

    If the fiber is well soaked in the resin, there should be no problem. But how are you going to get such a low proportion of resin? Probably (I am not sure), at first glance it will be seen that the fibers are not well locked. The resin, by the way, is more fragile than fiber and contributes to the mechanical properties of the laminate, although it does not greatly increase them. Delamination, with little resin, is likely.
    But in this forum there are true experts who can answer you with their authorized voices.
  3. gonzo
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    gonzo Senior Member

    A dry laminate won't have enough resin to bind the fibers together. It may increase the tensile values per weight, but will also be less stiff and tough. Not all mechanical properties are increased.
    fallguy likes this.
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    I don't even know you could get that low even in theory, cherry-picking the fabrics, and using epoxy resin. I think duflex panels are 50% or thereabouts, 25-30% is a hell of long way south of that.
  5. ondarvr
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    ondarvr Senior Member

    You can get into the 70% glass range, but you need to fully wet out and envelope every strand of fiber.

    Too little resin and there’s nothing holding the fibers in place.
  6. upchurchmr
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    upchurchmr Senior Member

    Prepreg is about 30% resin.
    Lots of technology and work to get there.

  7. fallguy
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    fallguy Senior Member

    You can achieve resin contents of around 35% using vacuum, but you have to go max pressures and you can't really do that with any low boiling point resins. Typically, anytime you get underneath the 35% mark, you are starting to starve the glass, except for, of course prepegs.

    Every contributor has made valid statements and perhaps the most important point is what will happen under starvation. And that is delamination.

    Most of my wetbag work we tested at resin contents of about 35% which was done by using maximum vacuum with 10mm bleeder release films. We tested those laminates versus hand laminated work side by side with some simple impact testing and I was really surprised that the lower resin content performed much better at hammer impact than the hand laminated which was running at about 50% resin. The more resin, the harder the laminate and the easier to break I suppose...although try breaking a glob of epoxy off the shop floor! To this day, I still worry about whether we had enough lock between glass fibers at our percentages. I jumped up and down on some of my panels with 220 pounds in dynamic efforts and the 12mm panels performed very well.

    I was very nervous about having delamination problems at my lower rates of 35%, so was please to see the hammer and bounce test results. However, I would be even more nervous if we ran as low as the numbers you are stating. It could probably be done with low viscosity resins and very open release films, or by preheating the resin to drive the viscosity up (I believe prepegs are heated, but that is way outta my ballpark). My point here is that I would get very nervous about being resin starved below the numbers I was getting.

    Be careful what you wish for...35% or 40% are already pretty low

    edited later~it should be noted; most of the methods will require a full wetout of the glass and then removal of excess; so you don't use 35% resin in a 35% layup; you still use 45-55% resins for wetting out and the rest is removed under pressures and discarded...there is a lot of wastage in reducing resins in the laminates for the typical person; I don't know enough about prepeg manufacturing to comment on the resins wasted in that process
    Last edited: Jan 24, 2020
    TANSL likes this.
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