Plascore vs corecell flexural rigidity

Discussion in 'Materials' started by fallguy, Nov 16, 2018.

  1. fallguy
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    fallguy Senior Member

    is there a simple way from typical tds to compare the two products?

    Which rating is needed?

    I am comparing Gurit Corecell M to Plascore 5# pp honeycomb with veil.

    Just want to know which one will deflect less over the same span.

    Thanks.
     
  2. Sparky568
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    Sparky568 Junior Member

    Did some test panels some time ago. 2 X 2 (feet) square panel of 1/2” gurit (scored) and carbocore. One set of each panel had a simple layer of 1-1/2 oz. csm both sides. The second set a single layer of 1708 on each side. Resin was gp ortho polyester. I can’t give you specific engineering or scientific data but can say in each case the the gurit panel was stiffer. In the end I went with the carboncore as it was sufficient for my application and cost.

    Your decision may be based on the same. I can say exposed edges of foam panels are much easier to deal with than the carboncore. In some cases I am actually finishing the honeycomb panel with a 1” strip of foam, routering the edge and then glassing the whole thing together. Hope this helps.
     
  3. fallguy
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    fallguy Senior Member

    Thanks for the reply.

    The big reason it is so attractive is the panels are available at 60" x 120".

    Someone told me it was more rigid than corecell, but I doubted them.

    The edge treatments are definitely going to be interesting. I am thru bolting the edges of two panels every say 16" around the perimeter, so those will ne through holed and refilled. I expect to do the same as you. Once the panels are glassed; rout and backfill with some thickened epoxy.

    I am trying to decide if to attempt vac bagging. My table is not 60" wide, but I could build side panels for it and just bag the bottom and make it work. Buy bigger bag, etc.

    I think I can reduce resin content by 40-50% bagging. So, say I use 21 oz triax, a hand lam is 21 oz resin per 9 sqft vs 11 oz vac bagged. Or for a 4x8 panel 32/9*10 oz times both sides. Or 640/9, call it 6.5# lighter. Just not sure the savings is worth all the work as well as pp with veil bonds. Maybe to ensure flatness; I'm forced to bag it.
     
  4. Ad Hoc
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    Ad Hoc Naval Architect

    Deflections are based upon several aspect of the arrangement.
    However for your question, assuming all things are the same, then it is down to the 'EI', but since assuming the "I" is the same (like for like) it is about the "E".

    Thus what is the difference in the E between to the two materials?
     
  5. Sparky568
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    Sparky568 Junior Member

    I know what you mean. I made a 4' x 10' layup table, the biggest I could fit in my garage. I recently made a large panel that was 13+ foot long. I just did it in two layups. I bought 4X8 sheets (cheaper shipping) and used scraps from leftover cuts from other pieces. Just glued them together using hull and deck putty.
     
  6. fallguy
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    fallguy Senior Member


    Sorry E?
     
  7. Ad Hoc
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    Ad Hoc Naval Architect

    E = Young's Modulus.

    It is essentially the slope of the stress-strain curve of a material. The value quoted is within what is called the elastic region of the curve. As shown below:

    [​IMG]


    But this wont really answer your question. Why..??..because these are ostensibly 'foams'.
    One doesn't use a foam by itself as a structural member. It has a laminate, a skin, either side. The skin, either side of the core, is what provides the stiffness, the "I" in the deflection calculation. The "I" is also based on the distance apart of these 2 skins.
    The core, which is the foam, of whatever you would like to use, plays no part in the strength/deflection calculation. The core, in this case the foam, of whatever type you select, carries the shear load. Thus the choice of core, foams, is based upon the amount of shear load you wish to carry per unit load application area, not deflection, per se. Unless of course you are using just a foam with no skins and nothing else!
     
  8. Sparky568
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    Sparky568 Junior Member

    Unless you are building an entire boat with this stuff you don’t need an engineering degree. If you can estimate the max load to your application and orientation (vertical vs. horizontal) any of the manufacturers should be able help with the product and layup needed. BTW, carbon core also makes many different foams. I found them very easy to deal with. When I placed my most recent order with them, I ordered some of their foam as well as the honeycomb. I was leaning towards higher density foam but when I described the application I was assured the lowest density foam would suffice. And yes this is a shameless plug for carbon core. They could have sold me a more expensive product but leaned towards the customers need.
     
  9. fallguy
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    fallguy Senior Member

    Well, I was planning to use 21-22 oz triax. Only thought skin was all equals to simplify.

    But it does seem like one core might be able to span more than another core with less deflection.

    Intuitively, for example, a plywood core would be stiffer.

    The manufacturer said corecell has a higher shear and thus would be stiffer, but that didn't really mean much.

    Guess I'll know when I glass some up.
     

  10. Sparky568
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    Sparky568 Junior Member

    Trial and error for peace of mind is a good thing. The more you work with anything the better feel you will have. When I did my foredeck I told them I had transverse frames every 24 inches and a deck flange at both ends. They recommended 1” honeycomb and a single layer of 1708. Results are, it is very stiff and feels like something solid under you.
     
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