What type of adhesive to use with Divinycell H100

Discussion in 'Materials' started by Joshua Alexander Saxon, Feb 13, 2022.

  1. Joshua Alexander Saxon
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    Joshua Alexander Saxon New Member

    Little unconventional. I am not building a boat, I'm building a small car. I hope you can still help me. I am planning to use Divinycell H100 to build the chassis and I am wondering what type of adhesive to use to glue the pieces together. I hope this is allowed. Thank you.
     
  2. fallguy
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    fallguy Senior Member

    Epoxy. Raw epoxy precoat and final thickened epoxy with 1/16" vee trowel both sides with optimal joins of 1mm. Thickener is typically fumed silica.

    But this won't be strong enough alone for a car chassis; so this is not a structural schedule for laminating glass to the core, etc.

    You can also buy products like gelmagic. https://www.systemthree.com/products/silvertip-gelmagic-non-sagging-epoxy-adhesive

    But important to note you need to test components to meet your structural requirements. Not for me to give you qa standards.
     
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  3. Joshua Alexander Saxon
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    Joshua Alexander Saxon New Member

    Thank you, also probably worth mentioning that the foam is 1in thick
     
  4. fallguy
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    fallguy Senior Member

    Raw foam cores are not very strong.
     
  5. Joshua Alexander Saxon
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    Joshua Alexander Saxon New Member

    It's sandwiched between carbon fiber sheets. Computer analysis' have confirmed this will work.
     
  6. fallguy
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    fallguy Senior Member

    6061 Aluminum has shear strength of about 30,000 psi. Raw h100 is about 205 psi. So, it is important to note when discussing laminating advice when such a massive discrepancy between cores presents. The products are about 150 times different and shear would be critical in auto accidents.

    I accept no liability here. Just pointing out fair concerns when being helpful. The bond strength of epoxy is often noted in generic, untested terms of 2000 psi, which is also 15 times less than aluminum.
     
  7. rxcomposite
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    rxcomposite Senior Member

    If you are using the H100 as core, you can bond it with epoxy as its shear strength is greater than H100. Corebond will do.

    If you are using the core as an element of a design, such as a beam, you insert laminate in between. Usually when the depth to width ratio of the beam exceeds more than 1. This is because tall I beams are not stable when side loads are present, i.e. torsion.
     

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  8. Ad Hoc
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    Ad Hoc Naval Architect

    For an I-beam, you show, that's correct.
    But if it is a 'box' shape section, that's different. It has torsional stiffness and a shear flow area:

    upload_2022-2-16_15-47-39.png

    Where T=2.A.q..... A being the enclosed area of the closed cell - shown in black

    You only need to check the webs for buckling, and shear under the load...
     
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  9. Scuff
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    Scuff Senior Member

    How do you determine the schedule for the laminate between the cores?
     
  10. rxcomposite
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    rxcomposite Senior Member

    That would depend on a lot of factors. Are you just duplicating the shape if the old chassis and making glass over foam core core? Are you using hand layup epoxy?
    You haven't given us much information or drawing.
     
  11. rxcomposite
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    rxcomposite Senior Member

    This might give you an idea so that we are in the same page.
     

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  12. Scuff
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    Scuff Senior Member

    I attached the drawing for the ibeams for my boat. I think I misunderstood the drawing you provided. Ed just calls for csm between the layers of foam. Since I'm using epoxy would a layer of 6 or 8 oz cloth suffice?
     

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  13. rxcomposite
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    rxcomposite Senior Member

    Ok. Now we are on another page. I thought there is a similarity to OP's thread.

    When building up core foams, gluing it together is a practical idea. You don't need to increase shear by adding shear ties. There are several ways. Corebond (polymer type), epoxy mixed with microbaloons to form a slurry (coat both sides then trowel), or a light CSM of about 280 gr/m2 or less will do. with the exception of 1 and 2, it is a good idea to "hot coat" both surface with a light coat of epoxy to ensure max bond since some foam surfaces are rough.
     
  14. Scuff
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    Scuff Senior Member

    My mistake I misunderstood. Sorry to hijack the thread.
     
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  15. rxcomposite
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    rxcomposite Senior Member

    Scuff. That is OK. Seems similar. I reserve the mat interface for high density cores because I need high shear strength. Unfortunately, low density core surface is so rough, I have to use micro slurry to have a good bond.
     
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