Core materials - aluminum vs aramid honeycomb

Discussion in 'Materials' started by hospadar, Dec 27, 2016.

  1. hospadar
    Joined: Apr 2011
    Posts: 62
    Likes: 3, Points: 8, Legacy Rep: 30
    Location: Michigan

    hospadar Junior Member

    Hi!

    I'm wondering if anyone can elaborate on the working differences between aluminum honeycomb & aramid honeycomb - I'm having trouble coming up with a good discussion of the difference.

    From what I can tell:

    -aluminum: a little heavier, a little stronger?
    -aramid (nomex): lighter, but weaker?

    I'm really wondering:
    - What's the difference in strength-to-weight ratio between aluminum & aramid honeycombs?
    - Is aluminum more or less conformable the aramid honeycomb? (I'm going to be working with 1/8" or 1/4" thick honeycomb)
    - Is aluminum harder to laminate into a panel than aramid?
    - Is aramid more suitable for a small home project without all the proper equipment?

    Things that I can't use for this project:
    - pre-pregs
    - curing oven
    - proper honeycomb adhesive films

    Things I can use:
    - vacuum bagging
    - home-made molds

    I'm looking to make some small-ish very thin composite panels - Right now I'm planning to make my own thin s-glass or carbon plates then laminating them to the honeycomb core.

    I'm actually going to end up using this for some musical instrument soundboards, although I'm kinda practicing my composite-making skills for some boat-work later-on.

    For this particular project, any kind of water-absorbency issues of aramid aren't a problem since I hopefully won't be submerging the little guitar I'm making.
     
  2. upchurchmr
    Joined: Feb 2011
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    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    Do you have any information that honeycomb panels will act as a good sound bar?
    Personally I have no knowledge, but given that the sound board has to vibrate at the frequency played, I would be concerned that the adhesive will damp out the free vibration, and each separate skin might not be free to vibrate.

    At 1/4 or 1/8 thickness there might not be much concern about the contour for a typical guitar. There are different core construction if you are looking for a significant contour.
    Look up OX core as an example.

    My guess is that you are not going to be so concerned by strength to weight, but rather stiffness.
    Any reasonable sandwich construction is going to be lighter than a single skin, unless the acoustics drive you to an unusual layup.

    Do you really need an "ultra-light" guitar?
     
  3. hospadar
    Joined: Apr 2011
    Posts: 62
    Likes: 3, Points: 8, Legacy Rep: 30
    Location: Michigan

    hospadar Junior Member

    Aramid honeycombs are used pretty regularly in guitarmakig for "double top" guitars where the soundboard is made with a honeycomb core and thin veneer skins.

    Overall weight isn't important per se, but volume and sustain of the instrument is closely related to the stiffness/weight of the vibrating soundboard (specifically how much string energy is converted into soundboard motion).

    Mostly I'm concerned with the workability of the core material, I'm reasonably certain that aramid comb will work since the pros use it, but I don't know what particular factors keep them from using aluminum (str/weight? Incompatibility with wood? Difficult adhesion?)

    For this case, I don't reeealy care about sound, just want to make a laminate that won't fail right away and teach myself some composite-building skills along the way.
     
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