Hi everybody
I have done VIP but I was wondering if someone can help me with the VIP using divinycell as a core. what is the order of the lay up ? I am planning on 1 layer carbon 3k, 2 layers of E-glass 9 oz and 1/4" divinycell …
mold, carbon, glass, glass, core, glass, glass, carbon, peel ply, flow media and bagging film?
or is it better to make each side separately and then compress it over the core with some weight or clamps?
it is for a flat panel roughly 60" by 20" (you might have guessed by now that the part is a front diffuser )
However if you have any suggestions on the materials too please let me know.
Thank you
You’ve got it right, just put an infusion grade perforated film between the peel ply and flow media( helps with removing the flowmedia).
Do it all in one go. We typically perforate the core at approx 25mm centres / 1mm diameter to feed the bottom laminate.
Being a front splitter you may want to increase the core thickness, of course in depends on how far apart the fastenings are and how much panel you have hanging out the front of the bumper.
core will need knife cuts and perferations.
While you don’t NEED to use perf. release film, or scored foam…it will help. I punch holes like what Brad1 mentioned. You can also make thin channels for the resin along the infusion direction. One core I have has 1mm channels cross cut on 1" or so centers. It helps.
As long as you can splice the layers of fabric, and stagger them well, you can do the whole length in out shot. Might have to make a large bag out of 2 pieces and tacky tape. Peelply and distro media can just be layed on top of each other randomly. Fabric you want to make sure the seams don’t line up!!!
As for mounting points. Do not bolt through the foam core. Cut around that area and either add extra layers of fabric, G10/FR4, or metal inserts.
Thank you Brad1, hojo and riff42 … now too make sure I understand correctly you mentioned to use infusion grade perforated film between the peel ply and flow media. is this what you were referring to ?
http://www.fibreglast.com/product/2989/Vacuum_Bagging_Films_Peel_Ply_Tapes
and also to perforate the core itself i should poke holes all the way through the core and create channels … how deep should be the channels ?
however I did not understand the part that riff42 mentioned about :
Peelply and distro media can just be layed on top of each other RANDOMLY. Fabric you want to make sure the seams don’t line up!!!
The RANDOMLY part and not lining up the seams… can you please explain more …
I have never made a big part like this so should I cover the whole area with flow media?
thank you again for sharing your knowledge.
A seam in 1 layer of fabric should not line up with the seam in the next layer. Stagger them at least 6 inch.
As for grooves: Pressing chicken wire into the foam (and removing it again) works wonders. You need only a faint depression when you are using perforated foam. You only need it on the bottom part.
The goal is to get an infusion that runs SLIGHTLY faster on the bottom laminate than on the top laminate. For thicker laminates a layer of CFM (continuous filament mat) works wonders. I have a 150 gr/m2 (very thin) one for that.
so by staggering you mean the top (outer) layers of reinforcement should be larger in size than whatever goes underneath (closer to the core), right?
May I ask where to lay the CFM? Touching the mold surface or the core surface (both options spaced between core and mold skin)?
In my case I am planning uni glass 150g/m at 0º, uni carbon 150g/m, at 45º uni carbon, 150g/m at -45º, Core, uni carbon 150g/m at 45º, uni carbon 150g/m at -45º,uni carbon 150g/m at 0º.
With staggering you mean overlapping?
Do the holes in the core increase the weight of the laminate significantly?
My wing chord will be 1,2m. How wide would you build the flanges?
Would you recommend using a semicircular tube on the positive plug to include a semicircular profile into one flange for positioning and then putting a circular tube on one side of the mold to get another semicircular profile on the other mold side and therefor guaranteeing both mold side fit together?
Thanks
Not neccesarily. As long as the butt or overlap seams in the first layer are more than 15cm (6") away from the second laminate. So if your rolls are 50"wide, then you can shift the seams 6" to the left or right, in the second layer.
mostly against the core.
In my case I am planning uni glass 150g/m at 0º, uni carbon 150g/m, at 45º uni carbon, 150g/m at -45º, Core, uni carbon 150g/m at 45º, uni carbon 150g/m at -45º,uni carbon 150g/m at 0º.
what is the glass doing there? In terms of strength it will not do anything. Need the thickness?With staggering you mean overlapping?
yes and no, staggering your overlaps means shifting the overlaps so no 2 overlaps end up on the same spot.Do the holes in the core increase the weight of the laminate significantly?
yes, somewhat. Depends on the size of hole, of course. Calculate the extra resin, and also keep in mind that the foam surface eats some 250-500 gr/m2 of resin.My wing chord will be 1,2m. How wide would you build the flanges?
I like flanges to be some 10-15cm wide.Would you recommend using a semicircular tube on the positive plug to include a semicircular profile into one flange for positioning and then putting a circular tube on one side of the mold to get another semicircular profile on the other mold side and therefor guaranteeing both mold side fit together?
Thanks
yes, you can do that. Anything will work, basicly. The challenge is to get things absolutely airtight. If all else fails, you can attach a vacuum bag on the outside of the seam, but that is a lot of work. Another option is to incorporate a “RTM light” seam, but the devil is in the details with that option.
Thanks a lot for sharing your knowledge.
what is the glass doing there? In terms of strength it will not do anything. Need the thickness?
Gel coat is fairly heavy and doesnt allow me to inspect that the infusion was succesfull. So I didnt wanted to use it and thought a first layer of glass would allow to sand a little bit in order to do the finishing on top of the superficial glass layer and protect the carbon.
yes and no, staggering your overlaps means shifting the overlaps so no 2 overlaps end up on the same spot.
Ok You mean two overlaps shouldnt cross each other.
yes, somewhat. Depends on the size of hole, of course. Calculate the extra resin, and also keep in mind that the foam surface eats some 250-500 gr/m2 of resin.
I thought about using filmed honeycomb. However this material lacks channels and holes. Is it therefor unusable?
Can I lay the spiral tube into the semicircular pattern of the mold?
About the layers: see attached. The top one is ok, the bottom one is less ok, as it creates a big clog of fiber.
When butt-seaming, things are even worse. Then you end up with hardly any strength on that spot.
tanx herman … great, now i get the seam line part 
I ordered some divinycell foam yesterday but they had to cut the sheet into smaller pieces ( quarters I believe) for shipping. now do I need to glue the pieces together before vip and if so, would hot glue work?
As for the seams generally no seams should bisect an underlaying seam (overlap). 1/2 inch overlap is preferred in most applications I’ve ever delt with. Look at the seam lay up at try to get intersections to fall out of e o p. This is the added benefit of using unidirectional prepreg as it needs only adjacent overlaps where bi axial and cloths need overlaps in both axis. Your sketch is 2d so bottom picture is deffinately bad but top is bad to as it creates a linear direction of seams running in a sing axis. If you are truly clocking your laminates your seams should also clock with corresponding angles to the above and below ply with Attention to the ply at hand.
A properly layed composite that bears loads in 360* often times has an almost abstract array of print through that reveals the underlying overlaps. Looks like a bunch of random crisscross under the surface.
Keeping your over laps linear, say all following the same axis even though you are clocking your plies actually creates a laminate that is stronger in one direction and can later propagate disbonds. The overlaps will give thickness and focus stress in a places you don’t want stress concentrated.
Overlaps create a small amount of strength in a single direction assuming the overlap is in one direction. On skins this would be bad. Non critical areas like fairings or scoops it’s not a big deal. You also have to think about what happens in the overlaps during the infusion. Is it getting the right amount of resin…
Sorry for jumping in here I hope I’m not throwing abstract ideas into a well planned design. I don’t quite understand exactly what it is you are making but I’m hearing overlaps and wing cord in the same discussion.
I’ve seen overlaps run parallel on leading edges as well as run with the spar.
Cores are generally bonded together with film adhesives when the core is formed. Just hot glueing it and placing it in the laminate… Is a no no. I wouldn’t fly on that.
So if I lay ±45º layers it wouldnt be good to have an overlap every meter pointing at +45º?
I should be alternating an overlap at +45º and one at -45º and always avoiding that both cross each other.
In the case of 0º overlaps the preference is to let them overlap at the spar glueing section or the leading edge of the flap and trailing edge of fixed wing section.
I thought about using the following layup schedule:
100g/m2 bi glass, 160g/m2 uni carbon 0º, 160g/m2 uni carbon +45º,160g/m2 uni carbon -45º, 150 CFM, Core, 160g/m2 uni carbon -45º, 160g/m2 uni carbon +45º, 160g/m2 uni carbon 0º,100g/m2 bi glass.
Would the two layers of 100g/m2 bi glass against the mold skin and against the infusion mesh be problematic to wet out correctly?
Thanks a lot for your advice
Biggest factor is what direction your strength is needed and Taylor your laminate with regard. There is software out there that places overlaps in the proper areas using formulas that engineers strength characteristics into the laminate because of overlaps and seams. This is more prevalent in faster than Mach aircraft and more so in composite helicopter blades. Not so much attention is paid in general aviation and home built projects.
Again… Sorry for bursting out in your discussion.
So long as you don’t have bonded structures underneath you are fine. -45/+45 per meter. If you do have underlaying structures you will have thickness irregularities. 0* at spar bond is correct and at trailing edge seam. You want continuous thickness at rib bond lines so no overlaps or intersections over this area. Say a 45 cuts the center wing box right in the middle. bad. intersections over core is totally fine. Spread your laps evenly -45/+45 along the leading edge so when you glue the leading edge you have evenly spaced laps along the length of the wing or flight control.
I had to draw you layup on paper… To understand.
What width is your fabric??? This will help you figure overlaps. And yes overlaps can give you disbonds. Dry areas.
Also wing cord. Material width and wing length should help you figure 45. Intersections. Lol berridos you really got alot to think about. Herman is on point with the chicken wire trick. I’ve seen cores have small profiles machined into the core to allow resin flow.
Berridos member tet is also a very very helpful resource on this forum as he has a wealth of experience in aerospace composites.
You can’t go wrong with a balanced stack and evenly spaced overlaps and interactions. The less the better.
On conplex shapes like fuselage to wing root fairings overlaps and plies get congested and overlaps become a problem.
I think you are fine but with 42" width fabric and 4 plies you will end up getting overlaps every foot or so @ 45 if that makes sense.