FRP bonded connection calculations

Discussion in 'Boat Design' started by boats_designer_fr, Jan 31, 2019.

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  1. Ad Hoc
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    Ad Hoc Naval Architect

    Agreed, you do not know nor should you post non-sequiturs.

    And yet:

    etc etc....and yet ....you cannot resist posting on a topic subject you clearly state from the outset that you know nothing about it nor how to calculate it, yet constantly and consistently do provide an opinion. An opinion that is based on zero knowledge of the subject at hand, by your own statement.

    So, please, for the sake of the OP and others that wish to understand how to do these calculations and learn, just remain quiet and let others (without egos that feel the need to keep posting) comment as required ..
     
  2. TANSL
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    TANSL Senior Member

  3. Ad Hoc
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    Ad Hoc Naval Architect

    Further to my previous comment, i'll explain:
    Your 2nd image:

    upload_2019-2-6_10-39-34.png

    For the core to fail at the locations you note, this woudl imply that the stiffness of the hull, noted by the 2 red arrows, is less than the stiffness of the core.
    In general composite design, this is never the case, if designed correctly. It would be like having a steel core with a sponge laminate. The core, has a much lower E an hence lower structural stiffness, EI. Two skins moved progressively farther and farther apart become stiffer and stiffer, the I. The core is designed for for only one purpose, to carry the shear load. Thus it is a simple matter of Force/area. Not forgetting the 'area' is along the width of the panel.

    Then looking at your first image:
    upload_2019-2-6_10-44-19.png

    All the locations noted by the arrows (only shown on one side for clarity as it occurs on both sides of the web) are load paths. This is where the load is transferred from the web to the hull structure. All these locations have higher E than the core and as such, their relative shear strength shall be greater. And thus we are left with...the bond of the upper skin to the core - noted by your red wiggly line. Even by inspection the amount of area that this covers will be significant to the point the tensile load, as it will now be, on the adhesion of the laminate to the core will be low. Otherwise, if this is suspect, the whole structure and hull and ergo material properties selected are incorrect.

    Thus, to imply the core is suspect is meaningless and clearly reflects a lacking in the ability of very basic structural analysis.

    It is like saying...if the engines fail on an aircraft, the plane will fall from the sky...as if that is a revelation of expertise and knowledge of aircraft design.! ?
     
    Last edited: Feb 6, 2019
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  4. Mr Efficiency
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    Mr Efficiency Senior Member

    No specs for the laminate, no indication what the load magnitude is, not much at all, and no response since post #1 !
     
  5. rxcomposite
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    rxcomposite Senior Member

    There will be no core to fail if indeed there is a core. Even if it did, it was determined from early start.

    Panels are designed with a firmly fixed edges and uniform load. It is then checked if it will fail with a concentrated load on center. The outer surface is designed to carry the stress load (tension/compression) and the inner "core" with diminishing stress level from the outermost surface. The inner laminate in the shaded portion of the diagram can be a weaker laminate such as CSM, absorbent felt, coremat, or even wood. Cores for sandwich panels are evaluated for shear. If the analysis shows failure from early design stages (that includes the safety factors/allowable strength, not UTS), the fixture design is moot and academic.

    The OP is not asking if his panel design will experience a core failure. From the OP's avatar, he claims to be a boat designer_FR(P?). I am sure he has worked it out.
     
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  6. Alik
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    Alik Senior Member

    "The core is designed for for only one purpose, to carry the shear load" - this is design assumption, not the physics of material behavior, especially in such details.
    Also OP did not say this is part of hull structure. It can be any structure.
     
  7. Ad Hoc
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    Ad Hoc Naval Architect

    Sure, but all one has to do, if one wishes to be pedantic, is interchange wherever I have used the word - hull - or - hull structure - and place your own word describing whatever structural element it is....beit, tank, bridge, linkspan, house...etc etc....but, it does not change the fundamental of the analysis. Any structural engineer can tell you that. The description of said, is merely its reference point.

    Incorrect.
    This is not a design "assumption". This is basic structural mechanics. Again, any structural engineer can tell you that.

    This is called the properties of the material one wishes to use. It is basic metallurgy and any material science engineer will tell you that.

    Thus:
    Please explain without using your usual non sequiturs such as, referring to 15m chain plates, or opinions on peeling etc etc (which have nothing to do with the Q at hand)...can you please explain in structural engineering terms what it is you either disagree with or do not understand about the purpose of a core in composites. As your statement does not make any sense, structurally.
     
  8. gonzo
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    gonzo Senior Member

    In that case you should stop assuming it is a hull or, by that same logic, anything related to a marine design.
     
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  9. Mr Efficiency
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    Mr Efficiency Senior Member

    Has he came back to explain anything yet ? Nope ? No surprises there !
     
  10. Ad Hoc
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    Ad Hoc Naval Architect

    Hmmmm...let me think.
    What is the name of this website forum...is it:

    cake-design.net.....er...nope
    curtain-design.net....er...nope
    gardening-design.net....er...nope

    Hmmm...well, what is this website called:

    Boat-design.net.....well, bugger me with a prize winning leak. BOAT DESIGN.....for the hard of hearing that is BOAT - DESIGN :D
    Now, I may be going out on a limb here.....scary i know, considering the background noise loafers that still cannot answer a simple question yet post like they know what they are talking about....but and it is a very BIG BUT....the clue may be the name - that being BOAT and DESIGN.

    So Boat implies.....curtains....cakes...er nope! What is a boat then....since i cannot assume it is a hull...oh what a dilemma...what shall I do??? o_O

    Now as far as I know a boat goes on the water....and anything related to the water is also referred as - marine too.

    Thus, the one assumption i can make with 100% confidence is that you have nothing to contribute to this thread at all.
    For evidence - see the unrelated postings on this thread thus far....

    But such a reply again clearly demonstrates a lack of understanding of structural mechanics, period. Endless misdirection replies (see above) wont hide that fact!
     

  11. Boat Design Net Moderator
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    Boat Design Net Moderator Moderator

    OK, probably a good point to close this thread as it seems to be causing more annoyance now than going in a productive direction. To the OP (or anyone else reading this thread interested in the original question) if you have related questions to the original post, please start a new thread with as many details as possible so the answers can be as helpful as possible. Thanks to all who take their time to help others, and thanks to all for your help in keeping the forums a place where people are kind to one another. Thanks.
     
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