Infusing CarbonCore Plastic Honeycomb...

Discussion in 'Fiberglass and Composite Boat Building' started by Zac Penn, Jan 22, 2016.

  1. Zac Penn
    Joined: Nov 2015
    Posts: 27
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: Jacksonville, FL

    Zac Penn Junior Member

    I am trying to figure out my infusion plan for 4' x 8' sandwich panels of CarbonCore polypropylene honeycomb. I was going to have two layers of 1808 on both sides of the core. The honeycomb has a polyester veil that is thermoformed onto the cells acting as a scrim. I was under the impression that the plastic coating under the scrim created an air tight seal between the scrim and the inside of the cells. However I heard from someone yesterday that they believed the scrim coat was slightly porous and would allow resin to flow into the cells when it was vacuum infused. So that is my first question...
    Has anyone had experience with this material and successfully infused it without resin migrating into the cells?

    If the honeycomb is not porous, or only VERY slightly porous, then that fact alone makes it more difficult for the resin to travel along both sides of the core during the infusion. Usually a perforated or grooved core is used to allow resign to flow on both sides of the core. To eliminate that issue I was going to layup my mold as follows...
    Waxed aluminum mold
    flow media
    peel ply
    1808
    1808
    core
    1808
    1808
    peel ply
    flow media
    bag

    I was going to have the resin supply line on one 8' long side of the panel. The resin supply section of the mold will have the full sized sheet of flow media down first, then a small strip of flow media under the 8' long spiral tubing then another strip of flow media above the tubing and then the full sized sheet of flow media on top of that. This should hopefully allow an even flow front across the entire panel for the 50+ inches of resin travel.
    I was then going to stop the full sized sheets of flow media 6" before the end of the panel so the resin flow can slow down before it gets to the vacuum source spiral tubing.
    The vacuum spiral tubing was going to have at least three evenly spaced suction tubes with clamps so I can close those tubes off if the resin front gets to those sections 1st.

    I know 50+ inches of travel is a long way for resin to flow, but I was hoping with the flow media it wouldn't be an issue. Thoughts? Recommendations?

    Once I have this section figured out I will share more details about this infusion.
    Thanks,
    Zac
     
  2. Stumble
    Joined: Oct 2008
    Posts: 1,896
    Likes: 71, Points: 48, Legacy Rep: 739
    Location: New Orleans

    Stumble Senior Member

    Zac,

    Without any direct knowledge I would probably do a test panel to see. Just because the barrier is not airtight though doesn't mean it wouldn't be epoxy proof. This could actually be a big issue if the epoxy were to trap a vaccume inside the core. It could place the honeycomb under constant preassure.
     
  3. Zac Penn
    Joined: Nov 2015
    Posts: 27
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: Jacksonville, FL

    Zac Penn Junior Member

    Very interesting comment. I hadn't thought about the scrim being resin tight and once the fiberglass cured leaving a residual vacuum in each honeycomb cell. The core compressive strength is 275 PSI so having a constant 14.7 PSI inward pressure on the core wouldn't stress it very much. I will have to do some more research but it could actually be a blessing and possibly improve the shear strength due to the sandwich facings being compressed onto the core.

    I have placed an inquiry with the manufacturer and hope to get a response soon. I do not have all my infusion supplies acquired yet so a sample panel will have to wait. I am just gathering information right now.
     
  4. Tungsten
    Joined: Nov 2011
    Posts: 468
    Likes: 10, Points: 18, Legacy Rep: 75
    Location: Canada

    Tungsten Senior Member

    So your using polyester or Ve resin ?Dont use matt with epoxy.
    I have some plascore here not carbon core but with the same veil on it,Ive only vac bagged it and had no problem with resin getting into the cells.

    Ideally you want it perforated to infuse both sides at once,only need flow media one side then.Lots of options for set up but trying to go 4' isnt very good.

    If the core is not perforated and both sides at once then this may work, feed line goes around perimeter and flow media both sides with a resin break where your vac is.You'll have to test that.
    Now pending how thick the core is youll have to chamfer the edge 60 deg or so overlap the flow media and sit the feed on top so resin will go to both sides.You'll have to fill the cells on the chamfered area.Plan a resin break in the middle and youll have to drill holes so the vac can get through.I know you can buy infusion grade plascore that has holes in it.With perf core its works well you only need flow media one side feed line around perimeter and one cutting it in half so 2 4x4 areas vac and resin break in the middle of each.mold side comes out flat and shinny.

    Or one side at atime but youll have to bag to the core or resin gets underneath.This may distort the panel a little

    Another way is 3 feed lines the 8' way then resin goes 2', vac around perimeter but again you need perforated core to do both sides.
    edit;
    And why carbon core? seams odd to have an expensive core like that and then put glass and matt on it.
     
  5. rob denney
    Joined: Feb 2005
    Posts: 756
    Likes: 111, Points: 43, Legacy Rep: 436
    Location: Australia

    rob denney Senior Member

    Should work as long as the resin inlet can reach the media against the mould. Make sure the underside infusion media is not overlapped and the surface should be pretty good. Pulling flow media off peel ply is a messy job. Unless the media is release treated, use perf plastic. CSM is pretty much just added weight and resin. Ve does not need it, and against the scrim, nor will poly.

    I tend to fill from the middle, as there is less distance for the resin to flow. 2' is a safe max distance. Could get more with thicker/better flow materials. Test it and see. Having multiple inlets available and/or a portable inlet will solve any problems until you know how far your resin travels. See other post about peel ply as a resin stopper.
     
  6. Zac Penn
    Joined: Nov 2015
    Posts: 27
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: Jacksonville, FL

    Zac Penn Junior Member

    I am trying to stay as LOW COST as possible so I was hoping to use a polyester resin with a low centistokes value.

    I have also been contemplating using an extruded plastic mesh as the flow media. It would be made out of either PP/HDPE/Nylon and have a somewhat aggressive flow channels to aid in the long distance of the resin flow. Here are two options I am looking into...
    http://industrialnetting.com/xb1130.html
    http://industrialnetting.com/xn3019.html
    My two goals with using a not so common flow media would be to achieve a longer resin travel, and by using a stronger material have it be reusable. I hope to be making many of these panels and if I can reduce the consumables budget by reusing a flow media I would be very happy.

    I see what you guys mean about not needing the CSM on the 0/90 for infusion, however the thickness it provides is needed for my application. Due to the variables in the deflection formula for composite sandwich beams. Reducing the sandwich skin thickness, by removing the CSM, will reduce the total bending strength of the panel. Just a quick calculation using two layers of 1800 vs 1808 per side on the panel will increase deflection by .8" at the same span/width/pressure, but it will reduce weight by 12 lbs. In order to achieve the deflection I would have to go up one size in core thickness, which would change the weight reduction to only 4 lbs. But, the extra cost of the thicker core should negate any cost savings in resin/CSM (I think...I haven't really gotten that far yet to analyze the cost of CSM and resin per lbs)
    So I would rather have the thinner panel at an extra 4 lbs for pretty much the same price.

    As for peel ply material I was going to go with taffeta from the local wholesale fabric distributors to save cost. I have read good things but I haven't tested it side by side yet. Still just gathering ideas and suggestions right now. I will test it when the time comes.

    As of now the core is going to be either 1.5" or 2" thick depending on how my engineer comes back. I am going to chamfer the entire perimeter and use a filler in the open cells. I was unaware of the Plascore material but I have placed an inquiry with their company as well. I like the idea of not using flow media on both sides with their perforated infusion grade honeycomb but I don't want to increase weight too much. Finding out the "Resin Filled" volume of a 4'x8' panel was part of my inquiry with the company.

    I am still very new to composites, but I thought my pricing on the CarbonCore was reasonable and by far the cheapest option when it compares to balsa/foam materials. If anyone has other core recommendations that are in the same density range at a lower price I am very interested.
     
  7. groper
    Joined: Jun 2011
    Posts: 2,467
    Likes: 123, Points: 73, Legacy Rep: 693
    Location: australia

    groper Senior Member

    Don't use csm - have a look around and see what the industry is doing, nobody uses it in high strength and stiffness panels as it's mechanical properties are poor.

    By all means you can and should achieve skin thickness using more of the stitched fiber reinforcements.
    Putting flow media under your panel will ruin the otherwise perfect surface you can achieve off your mold. For this reason alone I would use a more appropriate core material for infusion.

    If you must follow this idea , then you can use continuous filament mat , like CFM except the fibers are continuing and not chopped and doesn't have a binder to hold it all together. CFM acts like a flow media - except you don't remove it when your done, it stays as parts of the laminate...
     
  8. rob denney
    Joined: Feb 2005
    Posts: 756
    Likes: 111, Points: 43, Legacy Rep: 436
    Location: Australia

    rob denney Senior Member

    A better option than filling honeycomb edges is to heat seal them. A household iron is just hot enough to melt the cells without affecting the scrim and can be used to chamfer and seal the edge and a whole lot of other stuff. Takes a bit of practice to get it neat, but easier than bogging it.

    Let us know how the net works as a distribution medium, please.
     
  9. Zac Penn
    Joined: Nov 2015
    Posts: 27
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: Jacksonville, FL

    Zac Penn Junior Member


    Thank you for your recommendations. I did some research after you said that and I don't really like the stitched CFM reinforcement options because they ended being too thick with too low of strength due to the CFM. However I did get introduced to the VectorFusion line of 0/90 stitched materials, which have channels between the roving to assist in resin flow. I need to get pricing so I can accurately compare all the options. Not having to use flow media is a big plus, so if these channels can allow resin to flow the full width of my panel then I am extra happy about that. As long as the costs accounted for. I just don't know if a infusion product is going to cost twice as much just because it is specialty.

    The surface of the panels are not of a concern to me. This is strictly a structural project so cosmetics are not very important. Granted I don't want it looking terrible, but the mold is strictly there to get the same shape out of each part, and not intended to provide a clean finish.


    Very cool idea. I can't believe I hadn't thought of that before. I will have to play with that on some sample pieces and see how long the process would take for the entire 24' perimeter of a sheet.
     
  10. Zac Penn
    Joined: Nov 2015
    Posts: 27
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: Jacksonville, FL

    Zac Penn Junior Member

    I think I may be in trouble unless you guys can confirm otherwise...
    Will the vapor barrier in CarbonCore honeycomb be strong enough to keep the resin out of the cells during infusion?
    I have had a hard time reaching the manufacturer for a response.
    I don't care if maybe 5% of the resin migrates but i can't just fill the cells up with resin and add all that weight and cost.

    I have been in communication with Plascore and they have told me for sure that their standard PP honeycomb w/ vapor barrier and polyester veil will end up filling with resin. They said I needed to use their Infusion Grade material because that barrier film is strong enough to keep the resin out of the cells, except for the perforated ones. So you are thinking to yourselves...Just use the Plascore material and shut up. Well they have a minimum 4 week lead time and do not have any material in stock. I have a trade show in 6 weeks and I need to have a total of eight completed panels on display. That will take at least 8 days. I also need to build and test two panels at 1.5" and 2" thicknesses to determine the proper size core to achieve the deflection desired. I don't want to just guess on the thickness for the large order and after 4 weeks be wrong, and seriously up shits creek.

    So does anyone have experience infusing this material that can set my mind at ease? I can get CarbonCore from FGCI.com by next Thursday but I don't want to waste my time if you guys can help ;)


    I don't know why I didn't think of it earlier, I feel kind of dumb now, but I am going to try and forgo the flow media on both sides and perforate the honeycomb in a straight line right down the center of the panel. The line of perforations will be 8' long and spaced out every 2" OC. This way I can have my 8' long resin feed in the center, like Rob Denney recommended, and the resin will only have to travel 2' to the edge of the panel towards the vacuum lines.

    Thanks,
    Zac
     
  11. rob denney
    Joined: Feb 2005
    Posts: 756
    Likes: 111, Points: 43, Legacy Rep: 436
    Location: Australia

    rob denney Senior Member

    the first rule of infusion (boat building generally) is to try something at a small scale first. Given your time and materials limitations, I would skip the infusion and bag the panels one face at a time. If your resin out time is high enough, you could do multiple faces with a piece of perforated mdf or similar between the panels.

    Depending on the application, I would worry about the shear properties of 2" thick plastic honeycomb. You might be better off removing/flattening the core and allowing the laminates to come together.
     
  12. Tungsten
    Joined: Nov 2011
    Posts: 468
    Likes: 10, Points: 18, Legacy Rep: 75
    Location: Canada

    Tungsten Senior Member

    Robs got the answer,easy and will work the first time.
     
  13. Zac Penn
    Joined: Nov 2015
    Posts: 27
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: Jacksonville, FL

    Zac Penn Junior Member

    Well rats... I was hoping someone had experience with this material I could learn from.

    The problems with hand laminating then vacuum bagging is time, space and experience. My laminate will be 52" wide x 106" long. I don't know how easily I can wet out a full layer on a table. Can I start on a 55" x 96" sheet of scrap starboard, wet out 7' or so, and then fold/roll the wet side so i can slide the remaining knit onto the table? Like I said newbie ;)
    I really don't want to bag/vac multiple times for a single test panel, so I would need to wet out two full layers of laminate, and four reinforcing strips, quick enough to transfer/position/bag/vac while the resin can still easily travel out of the laminate.
    How close to gel time can I get and still successfully full out excess resin?

    I am going to try contacting the manufacturer again today and see if I can get a straight answer.
     
  14. Zac Penn
    Joined: Nov 2015
    Posts: 27
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: Jacksonville, FL

    Zac Penn Junior Member

    Well I was able to talk with the manufacturer today and they confirmed that you shouldn't vacuum infuse the raw honeycomb sheets. What he suggested as the cheapest and easiest option would be to wet out the veil on both sides and wait for it to gel. During that time, you can prepare the mold and first layer of laminate. Once gelled, I can carefully place it onto the mold and then finish the laminate and bag.
    While this is not the ideal setup for the future, it will allow me to infuse the first test panels and experiment with the perforation placement in the core.

    Please if anyone else has experience with this material, feel free to comment away. I will update once I get my hands on the materials.
     

  15. rob denney
    Joined: Feb 2005
    Posts: 756
    Likes: 111, Points: 43, Legacy Rep: 436
    Location: Australia

    rob denney Senior Member

    There are long pot life resins available which will give you plenty of time, but require a moderate post cure (blower heater, electric blanket, etc). Depending on what you are testing for, you could lay them up without vacuum. Do one side, leave it to cure, flip it and do the other side. One panel a day, easily.

    If this is not an option, then start testing. Get a sheet of window glass and some infusion materials and infuse some 2' sq sample. Once you get that right, have a go at a big one. Hand lay some as well, and compare weight, stiffnessand breaking loads. Or, use foam which is much less likely to be an infusion problem, and in 2" thicknesses, less likely to have structural problems.
     
Loading...
Similar Threads
  1. ahender
    Replies:
    4
    Views:
    317
  2. rob denney
    Replies:
    53
    Views:
    1,128
  3. CristianJ
    Replies:
    4
    Views:
    848
  4. Dejay
    Replies:
    44
    Views:
    4,272
  5. Tungsten
    Replies:
    30
    Views:
    3,502
  6. svquintana
    Replies:
    20
    Views:
    8,043
  7. Jetboy
    Replies:
    17
    Views:
    2,647
  8. nicste
    Replies:
    4
    Views:
    1,390
  9. Steve W
    Replies:
    201
    Views:
    20,989
  10. dshowalt
    Replies:
    5
    Views:
    1,721
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.