Just guessing here based on previous experience. First they laminate the ply sheets individually on glass "molds" using a vacuum bag. Then they probably trowel on a very thick epoxy adhesive on the back side of the first sheet, then lay the honeycomb and finally apply the top layer with epoxy on the back. All of this gets vacuum bagged to ensure uniform adhesion and thickness.
Easy to say they glued it together with epoxy and vacuum bagged it.... But I'm also curious what their actual process is. I wouldn't be surprised if they're using a layup process I'm not familiar with that gives the honeycomb better seating in the panel -being that it's structural and FAA. 🧐
If you come to germany, I can give you a tour :D I work with those panels, we are manufacturing panels and structures for satellites and other stuff for European Space Agency (European NASA) :D
@@michalgabco6194 Hi Michal, I am from Germany. Is the offer still actual :D? I am also working with composites and I would like to see different processes. Oskar
Back in the early seventies a company I was affiliated with made alveolate, prefab walls used in designs put up all over Africa. It’s funny to see the same ideas now used in aircraft. I’m surprised it took this long but I’m glad to see it happening. It’s a brilliant concept. You guys rock!
These videos are great and really seem to energize the community following the DarkAero 1’s development-keep up all the great work your doing along with the whole teams keen attention to the details. It goes a long way in helping the prospective DA builders come to appreciate and develop confidence in the design decisions YOU have made and continue to make as well form an emotional connection the plane, its design and your family-I wanted to say DarkAero company but for all intensive purposes, you and your brothers are the company. So the other thing about these videos is that everything they answer leads to yet more questions-questions in a good way though. Here are some that spring to mind: • Is there galvanic corrosion risks between the aluminum honeycomb and carbon fiber skins of these composite panels? • Assuming this was an issue, how were you able to assure that the edge of the aluminum honeycomb does not come in direct contact with any carbon fibre in the skins, during setup, bonding? • Most of your videos show the team applying adhesive to both surfaces to be bonded (all-be-it most, if not all, were of carbon fiber-to-carbon fibrer bonds) and much care was used to remove excess adhesive to keep the parts as light as possible. So how were you able to avoid using excess adhesive when making these panels yet not have any places with voids in the adhesive were bonding failed? • Do you use any nondestructive methods inspect and test the quality of the completed composite panels prior to them being used in production-for adhesion between the materials perhaps the use of ultrasound, x-ray, or the old rubber mallet & the human ear trick and for corrosion risk perhaps dielectric or conductive tests between a variety of points on the panels carbon fibre skins and the aluminum honeycomb core. • Why did you choose aluminum vs aramids or some other honeycomb core material when making these panels? • Was is the thermal characteristics of the aramid honeycomb core which you were referring to in the video when you rejected the samples of the commercially available panels or was it something else? • I understand why using honeycombed aluminum core composite for the firewall makes a lot of sense because, despite, using a titanium heat shield on the engine side of the firewall, aluminum alloys can maintain their rigidity and structural integrity for many 100°F higher temperatures than aramids. Without an extinguisher system, this fire would generate heat which could quickly get beyond the breakdown temperatures of the epoxy resins in the carbon fiber skins, and in the aramid honeycomb structures as well as the adhesives used to bond the composite panels together. In case of an in flight engine fire, keeping the the structure to which the engine mount and nose gear are attached, the firewall intact, would seem to be a prudent choice, but the internal structures in the wing would not seem to share the same risk whether the DA-1 is on the tarmac or in flight. Wouldn’t aramid or S-Glass honeycombed cores make for a lighter panel in these none engine compartments areas? • Are you anticipating that runaway solar induced thermal loads could be absorbed into the wing and thereby could compromise its internal structures? • Are you be trying to mitigate risks and increase the survivability of a fuel fed fire in the wing while at altitude? • Have you conducted proper destructive testing of samples from your honeycomb panels, during development to assess their true characteristics for engineering purposes. • Are the edges of the inner edges of the CNC cutouts in the wing tank areas sealed or is the aluminum honeycomb core exposed to the fuel in these places? • Although no pilot should willingly fly into an active lightning storm, what are the risks associated with a lightning strike--to the pilot and passenger directly, the electrical systems, the DA-1’s structural integrity and the fuel and the lubrications system? And what design and engineering decisions have you made to mitigate these risks?
Have you folks tested the resistance of this honeycomb to fuel intrusion? People in the composite boat building world have lots of stories of waterlogged foam cores. I'd like to hear that you kept a sample honeycomb panel in a jar of mogas for a year, and then measured weight gain. I'd like to hear that the edge details were as they are fabbed in the wing.
So I have seen those panels in use on the C-17 and my recollection is they are super strong for the weight but watch out for any water in the panel because it will freeze and delaminates the panel.
I agree. they stated that one of the panels made by a outside mfg was puros and would allow fuel to migrate into the core cells, well ill tell you there is no carbon panels that can be mfg to be completely sealed. they make a tank sealant that can be applied that will seal the carbon but again this adds weight. I'm curious if they run a wet wing or dry wing fuel cells
Your library of videos is excellent. You might consider a video showing stress to failure of carbon fiber parts and aluminum parts. If done right It could get tons of views
OK, more serious question. Edge treatment: I can see you have only a few exposed edges for your panels, mainly in non-structural areas like cockpit arm rests. In order to avoid core erosion, do you specify any particular edge treatment?
@@DarkAeroInc Hey loving the videos. Will Dark Aero be selling just uncut panels to other builders? I would be interested in using this kind of panel in place of Klegcell foam core panels and just wondering if you think that could work. Also curious why you went with a 1/2" panel instead of the 1/4" ones you were ordering from other vendors? Thank you for all the knowledge shared already.
Thats actually not really a problem. The interior of most planes (like Airbus A380, , mainly the side/window panels, are largely made out of nomex/aramid honeycomb filled with resin.
@@beachboardfan9544 yes, the honeycomb is good against horizontal forces, you can stand on it all by itself. The resin strengthens it against lateral forces and basically turns the whole piece into a single composite. I saw it at one of my company's subsidiaries, they are a tier 1 supplier for Airbus and basically make the whole interior excluding seats. The venting ducts are the craziest part, completely out of carbon fiber and spanning the a large part of the space above the cabin.
I would love to see a test of the different panels. I’m looking to make the strongest panels possible and would love to see the results on different amount of layers and honeycomb thickness.
Good question. I wonder if the aluminum honeycomb would create a Faraday cage? Don't they embed a copper lattice into the layup on airliners using extensive composites?
Dan Mallery Well I’ve only got about 3000 hours in the 787 and the only time we’ve ever had a problem is when we were parked on the ramp at Shanghai and got struck by lightning. It blew up the ground power terminal and we spent an extra couple of days there. I highly recommend a club called Manhattans ! ; ).
We don’t have good data on that because we haven’t completed lighting strike testing yet. However, we have been doing a lot of research on this and we are leaning on the testing and standards from the FAA (two good ones are the DOT/FAA/CT-89/22 and DOT/FAA/AR-40/13). The two big concerns are interference with the electrical system and fuel vapor ignition. One potential solution we are exploring is conductive coatings.
Are there any corrosion issues using Aluminium honeycomb with Carbon Fibre? When Carbon Fibre is used with Chrome Moly tubing, a plastic spacer is needed to separate the two materials to stop corrosion. What was the criteria for selecting the Aluminium honeycomb? What grade of Aluminium did you settle on and why?
For the webs inside the wing, what do you need the stiffness of the honeycomb for? Those webs should be under shear and compression and tension in plane. What out-of-plane forces do they see? I can see that the thickness of the webs makes them easier to handle and get into position.
Does the honeycomb sandwich build up pressure on a hot day? Windsurfing boards can delaminate if you forget to unscrew the vent and you leave it in the sun.
The internal cells of the honeycomb are sealed so they do build pressure with changes in temperature and atmospheric pressure. This caused some problems for us in our early days of panel testing. We had to come up with a method to bond the honeycomb core to the carbon fiber skin that was strong enough to withstand the large changes in temperature in pressure. Larger structures like the wing, VS, and HS are vented which is analogous to your windsurfing board example.
Fascinating! Quick question: What happens if a lightning strikes the plane, be it in the air or on the ground? If not mistaken, I believe that Boeing and/or Airbus mix in some kind of copper mesh within their composite structures to allow the electricity to flow (creating a faraday cage I´d imagine) and not generate any damage at the impact location. Is this a concern for DarkAero as well? Congratulations on this great work!
your presentation is really unique and informative .I am happy to see the progress of your airplane. wish you good luck. I am sure this will be very successful
good to see but you can also use the cnc and software for unidirectional thin ply layering. that way you reduce carbon waste and weight and increase strenght. the best sandwich core to date is foam core with carbon rods in pyramid structures. you can buy thin carbon rods and cut the foam in pyramids (pyramids can also be adapted for pressure areas) with CNC so you put the rods manualy and them put the other half of the foam (with holes also, the rods have to be in contact with the external carbon layers) and after you lay the thin ply with the cnc on both sides and then to the autoclave. this system can be improved with topology optimization software and several thin bulkheads
The question more has to do with the use of honeycomb core material. I can't remember now, but even if it's not paper, I'm concerned about fuel being trapped in the voids making the airplane unnecessarily heavier.
@@mavigogun You're right, it is brought up at 6:09. What I was referring to specifically, is the bonding joints between the honeycomb and the skin when the wing is assembled. If there is even one error/bubble in that bonding surface it could lead to a slow seepage of fuel into the sandwich structures that would, at minimum, increase the weight of the aircraft. Worse, possibly, is delamination and debonding at those seepage points due to thermal expansion/contraction cycles. The wing could become structurally compromised after a few years or so in the elements. Don't believe me? Look at how careful Mike Patey is when building his fuel tank. ua-cam.com/video/JZSGdM9cWjY/v-deo.html In that example he's just being very thorough to ensure there are no leaks. Also, notice how every cell of that tank has an access panel? There's a reason for that. Future repairability. His tank isn't even a composite tank!
@@Zalex612 It would seem fraught with peril, as complex as it is. Either they have developed blindered to this point, or they aren't sharing their solution. I reckon the second is more likely.
Having gone through the stiffness/weight numbers myself I found that surprisingly enough the aluminum was superior, at least when it comes to that one supplier whose products i was looking at.
Evan, we might do a video on this down the road but in the earlier days when we were moonlighting the company all we did was R&D and destructive testing on the panels. :)
@@DarkAeroInc This was more of a post production QA test to ensure you're not shipping parts where somebody mixed the resin slightly wrong or the vacuum was too high and sucked too much of the resin out etc etc. Just to verify that the material properties are as predicted. At the high end in my world, the incoming raw materials are also tested before you build anything with it.
Agreed that quality checks are critical. We have a set of QA checks and manufacturing procedures we use that are mostly proactive but we run some destructive tests as well. In the process of developing the panels, we had to determine all the variables that contribute to making a quality panel. One thing we learned was that on a panel as large as 4'x8', there can be variation across the panel if your process is incorrect. Testing a cut off scrap is only useful if you have the correct manufacturing procedure in place to ensure consistency across the whole panel. We follow a specific procedure to manufacture the panels and document that key variables are within acceptable limits. Who would have thought making a flat panel could be so involved! :)
Wait a minute - you say you didn't use one of the prepreg plates, because it had holes and wouldn't store fuel well - but surely you wouldn't expose a laminate directly to fuel without some sort of liner? Also, when it comes to foam/hex cores, isn't aren't the carbon and cured resins the most temperature-intolerant parts of the laminate? I thought aramid and aluminium were both more temperature resistant than carbon and epoxy.
Thank you for watching Invisty! Great questions! Laminates can be exposed directly to fuel provided that the chemistry of the epoxy used in the laminate is fuel compatible. Yes, typically the cured resin and foam cores are the limiting factor for temperature capability of a composite structure. However, there exists a wide range of epoxies and core materials that can be used which all have different temperature capability. We only use resins and core materials with temperature capability beyond 300 F. I didn't give out any specific numbers in the video but many of the 3rd party panels we tested had carbon fiber and epoxy skins with service temperature ratings of 180F and below.
@@DarkAeroInc Thanks for clarifying, my ignorance probably stems from only using composites for boats. I think the very idea of a kitset carbon panel plane to be ambitious and really cool. Hope you can pull it off with all the tricky engineering required.
When bonding a sandwich panel to the wing skins, do you add a "spar cap" or strip to interface between the edge of the panel to the wing skin. Curious about imprinting the substructure to the outer side of the wing skin.
I hope you guys have a good factory build center because all the glue joints for the wing skins have to be perfect. This is why the commercial gliders have single spar to ease the manufacturing because they only have to worry about the main spar, the ribs, the leading edge and aft spar. Good luck though. We need to have another composite kit that follows the Lancair 360 or the Glasair 3. However, few people can afford to build them.
I am very much interested in how you plan to build the gas tanks. From what I am hearing, it sounds like you will be doing wet wings. How does that work out with ethanol fuels?
Same Thoughts...a large helicopter manufacturer had made their tail boom panels with aluminum core... they had to redesign due to corrosion. I believe this comprised strength and caused problems.
@@jeffreygoyer7760 I would imagine the solution be either or a combination of anodizing the aluminum material, and an epoxy/fiberglass barrier. But let's see what their solution is.
The carbon fiber is electrically isolated from the honeycomb using fiberglass. The panels themselves are carbon - fiberglass - honeycomb - fiberglass - carbon.
Thanks for video. How do you join the shear webs from sandwich panels with the wing skins? Which adhesive do you use? I am concerned of an extra weight gain due to the adhesive which is absorbed by open cells of honeycomb. Also I am concerned of the joint between the skins of sandwich with the wing skin. How do you do surface prep before bonding?
Thanks for watching and the question! We just released a video on how we prevent galvanic corrosion on the DarkAero 1: ua-cam.com/video/yRpMZaU8zKw/v-deo.html
Awesome video as always ! Going to subscribe to the online courses very soon ! One question, I am building my own aircraft now, and I do hesitate between aluminum and aramid honeycomb for the main fuselage frames (both 0,6inch). With your experience, which one would you use? (with 2x210g carbon twill on each side of the panel, plus 50g glass each side if aluminum for galvanic corrosion prevention). Thank you so much ! Waiting for the DarkAero kit !
Does this have to be made with prepreg? Is the surface resin all that's used to bond the honeycomb to the CFRP? I assume bonding honeycomb to sheets after the cure doesn't yield great results and adds weight from extra resin....
Beautiful design for rigidity, strength and lightweight qualities. I wonder if the aluminium honeycomb was carbon also what the qualities difference would be? Answers would be interesting! Great video, liked and subscribed!
Is it more ideal to make the wing, vertical and horizontal stabilizer a whole piece of sandwich panel? (assume the honeycomb core can be made to fit the airfoil and accommodate fuel)
I didnt find a video from you about how to make the honycomb composite. From watching your videos, you prefer unfusion. But can that be used when you have a hoycomb with hollow space between the latyers of fiber/carbon on either end? Do do you prepare carbon panels and cure them and "glew" the carbon panels to both side of honeycomb? If you used a vaccum process, wouldn't the carbon want to go into each honeycomb hole& (and wouldn't the resin want to fill that hole if using infusion?
Really loving how this plane is coming together. Currently on a bit of a project with an old Mooney but I could see myself in a DarkAero in a couple years. One question -- Mooney types really tout the crashworthiness benefits of the steel frame that surrounds the cockpit in those airplanes. How have you guys thought about crashworthiness in this plane?
All modern race car crash structures are made from carbon fibre - it's much better at absorbing energy than steel, and also by not having any holes like you would in a steel frame it's much better for preventing puncture injuries.
So in theory could you make a whole plane out of folded honeycomb carbon panels including all the outer skins? Is there any structural weakening when you mill and bend the panels? It would be a very boxy plane but maybe an interesting proof of concept.
The folding plane concept as been applied on several air frames in the home build community for over 15+ years. Mr. Steve Rahm was the inventor of the process, using foam core vs honeycomb aluminum. pro-composites.com/FAP.html Vision airplanes was one of the most ambitious design using this technique. I think they are no longer around unfortunately. The basic concept is you can make a curve composite panel out of flat one by machining the inner layer, then bend the panel in a form, and they you re-force the areas that are cut with layers of carbon/fiberglass as to re-establish the overall strength. The Personal Cruiser is another plane design that uses the same concept. Here is a video on the assembly process. ua-cam.com/video/Sw7xafhj9ZI/v-deo.html Its actually brilliant, if you can mass produce quality flat sandwich construction. The mfg & assembly process becomes repeatable and at a lower capital expenditure as they are not investing in high cost molds and dies. For the builder its also great as you can ship parts relatively flat, therefore lowering the cost. All the while not having to form your own fuselage using traditional composite construct (Burt Rutan and such). These guys are on to something.
The YB-70 Valkyrie was built with an outer skin of stainless steel skins brazed to a stainless steel honeycomb. They had compound curves. They also had delamination problems. The SR-71, designed just after the YB-70, used sheet titanium instead. Leading and trailing edges, and the inlet cones and vertical stabilizer were initially an asbestos-silicone composite, intended to be stealthy. They may have given up on that at some point. It's amazing how long people have been using composite technology. The De Havilland Mosquito built during WWII was, in some sense, a wood/glue composite, as were some of the wackier German airplanes.
The honeycomb edges connect to the composite layers on a very small surface. How is it still a strong enough bond that can be relied on so much? How and when does it fail? It's fascinating.
I'm curious what the cost difference is between off the shelf panels and your own panels, and why aluminum core over an aramid core in your own panels. I'm also curious about your manufacturing method of these panels, I've only ever seen this done with pre-preg, and I know everyone has their own slight variations on how they make theirs; but I'm going to guess you manufacture, or buy, the carbon panels first, then bond them to the honeycomb, to avoid resin seeping into the honeycomb and adding dead weight, where in typical pre-preg pieces, the honeycomb is sandwiched between the sheets before bagging and curing.
Jim, thanks for watching and the comment. The carbon fiber and aluminum honeycomb are electrically isolated using a layer of fiberglass. We have a video coming out in the future that goes into more details on galvanic corrosion so stay tuned!
Would love to see how you bond the panels to the core structure.
They probably apply epoxy glue to both sheets, add the honeycomb in between and then vacuum bag until cured.
@@jimbit22 Wouldn't that pull the epoxy out of the wetted CF into the honeycomb? I'm curious about this too.
Just guessing here based on previous experience.
First they laminate the ply sheets individually on glass "molds" using a vacuum bag.
Then they probably trowel on a very thick epoxy adhesive on the back side of the first sheet, then lay the honeycomb and finally apply the top layer with epoxy on the back.
All of this gets vacuum bagged to ensure uniform adhesion and thickness.
Easy to say they glued it together with epoxy and vacuum bagged it.... But I'm also curious what their actual process is. I wouldn't be surprised if they're using a layup process I'm not familiar with that gives the honeycomb better seating in the panel -being that it's structural and FAA. 🧐
Super interested. The honey comb seemed flexible. I wonder if you could wet lay a lightly curved surface with honeycomb laminate.
The attention to detail in this build is outstanding. Can't wait to see this thing progress to flight trials.
🐔
Please Show us the Manufacturing Process you implemented your own honey comb panels, Thanks, Great Work Guys, Appreciate your work
It had been like 17 hours since the last video, I was getting concerned. 😂
I would love to see a video on making the panels. That would be interesting.
+1 would be great to see how carbon sheets are bonded together with honeycomb.
If you come to germany, I can give you a tour :D I work with those panels, we are manufacturing panels and structures for satellites and other stuff for European Space Agency (European NASA) :D
@@michalgabco6194 Hi Michal, I am from Germany. Is the offer still actual :D? I am also working with composites and I would like to see different processes.
Oskar
Astonishingly magnificent. New dimension of Engineering.
Hat off to all of you for your passion and doing what you love most !!!
Back in the early seventies a company I was affiliated with made alveolate, prefab walls used in designs put up all over Africa. It’s funny to see the same ideas now used in aircraft. I’m surprised it took this long but I’m glad to see it happening. It’s a brilliant concept. You guys rock!
Honeycomb sandwich construction in aerospace has been around since at least the early 1960’s.
Your videos are some of the best I've ever seen of a aircraft being fabricated. Please continue to be awesome
These videos are great and really seem to energize the community following the DarkAero 1’s development-keep up all the great work your doing along with the whole teams keen attention to the details. It goes a long way in helping the prospective DA builders come to appreciate and develop confidence in the design decisions YOU have made and continue to make as well form an emotional connection the plane, its design and your family-I wanted to say DarkAero company but for all intensive purposes, you and your brothers are the company.
So the other thing about these videos is that everything they answer leads to yet more questions-questions in a good way though. Here are some that spring to mind:
• Is there galvanic corrosion risks between the aluminum honeycomb and carbon fiber skins of these composite panels?
• Assuming this was an issue, how were you able to assure that the edge of the aluminum honeycomb does not come in direct contact with any carbon fibre in the skins, during setup, bonding?
• Most of your videos show the team applying adhesive to both surfaces to be bonded (all-be-it most, if not all, were of carbon fiber-to-carbon fibrer bonds) and much care was used to remove excess adhesive to keep the parts as light as possible. So how were you able to avoid using excess adhesive when making these panels yet not have any places with voids in the adhesive were bonding failed?
• Do you use any nondestructive methods inspect and test the quality of the completed composite panels prior to them being used in production-for adhesion between the materials perhaps the use of ultrasound, x-ray, or the old rubber mallet & the human ear trick and for corrosion risk perhaps dielectric or conductive tests between a variety of points on the panels carbon fibre skins and the aluminum honeycomb core.
• Why did you choose aluminum vs aramids or some other honeycomb core material when making these panels?
• Was is the thermal characteristics of the aramid honeycomb core which you were referring to in the video when you rejected the samples of the commercially available panels or was it something else?
• I understand why using honeycombed aluminum core composite for the firewall makes a lot of sense because, despite, using a titanium heat shield on the engine side of the firewall, aluminum alloys can maintain their rigidity and structural integrity for many 100°F higher temperatures than aramids. Without an extinguisher system, this fire would generate heat which could quickly get beyond the breakdown temperatures of the epoxy resins in the carbon fiber skins, and in the aramid honeycomb structures as well as the adhesives used to bond the composite panels together. In case of an in flight engine fire, keeping the the structure to which the engine mount and nose gear are attached, the firewall intact, would seem to be a prudent choice, but the internal structures in the wing would not seem to share the same risk whether the DA-1 is on the tarmac or in flight. Wouldn’t aramid or S-Glass honeycombed cores make for a lighter panel in these none engine compartments areas?
• Are you anticipating that runaway solar induced thermal loads could be absorbed into the wing and thereby could compromise its internal structures?
• Are
you be trying to mitigate risks and increase the survivability of a fuel fed fire in the wing while at altitude?
• Have you conducted proper destructive testing of samples from your honeycomb panels, during development to assess their true characteristics for engineering purposes.
• Are the edges of the inner edges of the CNC cutouts in the wing tank areas sealed or is the aluminum honeycomb core exposed to the fuel in these places?
• Although no pilot should willingly fly into an active lightning storm, what are the risks associated with a lightning strike--to the pilot and passenger directly, the electrical systems, the DA-1’s structural integrity and the fuel and the lubrications system? And what design and engineering decisions have you made to mitigate these risks?
La corrosione deve essere fermata!
Have you folks tested the resistance of this honeycomb to fuel intrusion? People in the composite boat building world have lots of stories of waterlogged foam cores.
I'd like to hear that you kept a sample honeycomb panel in a jar of mogas for a year, and then measured weight gain. I'd like to hear that the edge details were as they are fabbed in the wing.
So I have seen those panels in use on the C-17 and my recollection is they are super strong for the weight but watch out for any water in the panel because it will freeze and delaminates the panel.
I agree. they stated that one of the panels made by a outside mfg was puros and would allow fuel to migrate into the core cells, well ill tell you there is no carbon panels that can be mfg to be completely sealed. they make a tank sealant that can be applied that will seal the carbon but again this adds weight. I'm curious if they run a wet wing or dry wing fuel cells
Your library of videos is excellent. You might consider a video showing stress to failure of carbon fiber parts and aluminum parts. If done right It could get tons of views
How do you make your panels? Do you have fiberglass between the carbon and aluminum?
They are using fiberglass. It was subtly said in a previous video about composites used in manufacturing
Here it is ua-cam.com/video/mwTE4MamfVE/v-deo.html
Perfect thanks lancer2204
Loving these videos, I'm learning alot and it's inspiring me to make a build of my own. Thank you!
so great to see the other panels and reasons why you Mae your own. thx!
OK, more serious question. Edge treatment: I can see you have only a few exposed edges for your panels, mainly in non-structural areas like cockpit arm rests. In order to avoid core erosion, do you specify any particular edge treatment?
The exposed honeycomb will be sealed similar to other areas in the aircraft. We have used a thickened epoxy to accomplish this.
DarkAero, Inc Thanks!
Look into trimlok.com edge trim. Lots less fussy than epoxy backfilling and possibly a cleaner look. Probably a small weight penalty.
@@DarkAeroInc Hey loving the videos. Will Dark Aero be selling just uncut panels to other builders? I would be interested in using this kind of panel in place of Klegcell foam core panels and just wondering if you think that could work. Also curious why you went with a 1/2" panel instead of the 1/4" ones you were ordering from other vendors? Thank you for all the knowledge shared already.
So many juicy videos! Thank you!
How do you prevent galvanic corrosion?
Come ???
I am wondering this too.
They are using fiberglass. It was subtly said in a previous video about composites used in manufacturing.
@@Nicks675 OK Thanks.
look like carbon top layer?? maybe its fiberglass to aluminium then carbon on top of that?
Thank you for the great explanation. Good details and shows how much research you guys had to do before getting a move on things. Go Bucky!
Hexcel Corp. was using this Al honeycomb core technology back in the 70's for helicopter blades and snow skis as well as other applications.
Very informative and professional. Keep em' coming 👏
Thank you! :)
If you guys dont use pre preg how do you keep the honeycomb from filling with resin?
I would guess gravity, by having the wet skin at the bottom, directly on the table.
@@nraynaud I'm guessing its a process similar to this:
ua-cam.com/video/YRpu3pb2b3U/v-deo.html
Thats actually not really a problem. The interior of most planes (like Airbus A380, , mainly the side/window panels, are largely made out of nomex/aramid honeycomb filled with resin.
@@12346798Mann Filled solid?
@@beachboardfan9544 yes, the honeycomb is good against horizontal forces, you can stand on it all by itself. The resin strengthens it against lateral forces and basically turns the whole piece into a single composite.
I saw it at one of my company's subsidiaries, they are a tier 1 supplier for Airbus and basically make the whole interior excluding seats. The venting ducts are the craziest part, completely out of carbon fiber and spanning the a large part of the space above the cabin.
I've had some honeycomb cardboard and it is amazing how strong it is though thick. I can almost imagine how strong that construct is.
I would love to see a test of the different panels. I’m looking to make the strongest panels possible and would love to see the results on different amount of layers and honeycomb thickness.
appreciate the content so much guys!!!
This would be great for boutique auto manufacturing, since it bypasses much of the capital expenditure costs of starting an auto line.
Nice. How do you prevent the epoxy from going into the honeycomb?
What effect will an inflight lightning strike have on that method of construction ?
Good question. I wonder if the aluminum honeycomb would create a Faraday cage? Don't they embed a copper lattice into the layup on airliners using extensive composites?
Dan Mallery
Well I’ve only got about 3000 hours in the 787 and the only time we’ve ever had a problem is when we were parked on the ramp at Shanghai and got struck by lightning. It blew up the ground power terminal and we spent an extra couple of days there. I highly recommend a club called Manhattans ! ; ).
@@savagecub Yikes. Getting struck by lightning, even on the ground...better just leave the whole bottle. :-)
Dan Mallery
Ah hell, airplane was parked at the gate. We were already at the bar in the hotel when that happened !
We don’t have good data on that because we haven’t completed lighting strike testing yet. However, we have been doing a lot of research on this and we are leaning on the testing and standards from the FAA (two good ones are the DOT/FAA/CT-89/22 and DOT/FAA/AR-40/13). The two big concerns are interference with the electrical system and fuel vapor ignition. One potential solution we are exploring is conductive coatings.
Are there any corrosion issues using Aluminium honeycomb with Carbon Fibre? When Carbon Fibre is used with Chrome Moly tubing, a plastic spacer is needed to separate the two materials to stop corrosion. What was the criteria for selecting the Aluminium honeycomb? What grade of Aluminium did you settle on and why?
I was wondering about the galvanic corrosion issue, too. It seems concerning to me.
For the webs inside the wing, what do you need the stiffness of the honeycomb for? Those webs should be under shear and compression and tension in plane. What out-of-plane forces do they see?
I can see that the thickness of the webs makes them easier to handle and get into position.
I suppose you might ask that of any conventional wood-over-foam web.
Great explanation. Very well presented.
Stiffness increases with the square of the thickness!! Important in honeycomb structures.
stiffness is cubic? stress at skin is inverse of thickness squared?
Great Explanation of your process of elimination to get to the proper building materials of the Dark Aero!
The most famous honeycomb like structure is The Eiffel Tower ...
Very brillant idea !
Does the honeycomb sandwich build up pressure on a hot day? Windsurfing boards can delaminate if you forget to unscrew the vent and you leave it in the sun.
The internal cells of the honeycomb are sealed so they do build pressure with changes in temperature and atmospheric pressure. This caused some problems for us in our early days of panel testing. We had to come up with a method to bond the honeycomb core to the carbon fiber skin that was strong enough to withstand the large changes in temperature in pressure. Larger structures like the wing, VS, and HS are vented which is analogous to your windsurfing board example.
Fascinating! Quick question: What happens if a lightning strikes the plane, be it in the air or on the ground? If not mistaken, I believe that Boeing and/or Airbus mix in some kind of copper mesh within their composite structures to allow the electricity to flow (creating a faraday cage I´d imagine) and not generate any damage at the impact location. Is this a concern for DarkAero as well? Congratulations on this great work!
Also added advantage is absorbing vibration
your presentation is really unique and informative .I am happy to see the progress of your airplane. wish you good luck. I am sure this will be very successful
Excellent instructor.
Thank you for watching and the kind words!
good to see but you can also use the cnc and software for unidirectional thin ply layering.
that way you reduce carbon waste and weight and increase strenght.
the best sandwich core to date is foam core with carbon rods in pyramid structures. you can buy thin carbon rods and cut the foam in pyramids (pyramids can also be adapted for pressure areas) with CNC so you put the rods manualy and them put the other half of the foam (with holes also, the rods have to be in contact with the external carbon layers) and after you lay the thin ply with the cnc on both sides and then to the autoclave.
this system can be improved with topology optimization software and several thin bulkheads
Love this breakdown! Super excited!
Are you guys messing with Ti or MG?
Thank you for watching Andrew! We have a few titanium components but we haven't used any magnesium.
I'm a bit concerned about your fuel tank integrity. Would love to see the thought put into that design question.
Composite fuel tanks have been used for decades in marine applications
The question more has to do with the use of honeycomb core material. I can't remember now, but even if it's not paper, I'm concerned about fuel being trapped in the voids making the airplane unnecessarily heavier.
@@Zalex612 This was spoken to explicitly in the presentation.
@@mavigogun You're right, it is brought up at 6:09. What I was referring to specifically, is the bonding joints between the honeycomb and the skin when the wing is assembled. If there is even one error/bubble in that bonding surface it could lead to a slow seepage of fuel into the sandwich structures that would, at minimum, increase the weight of the aircraft. Worse, possibly, is delamination and debonding at those seepage points due to thermal expansion/contraction cycles. The wing could become structurally compromised after a few years or so in the elements. Don't believe me? Look at how careful Mike Patey is when building his fuel tank. ua-cam.com/video/JZSGdM9cWjY/v-deo.html In that example he's just being very thorough to ensure there are no leaks. Also, notice how every cell of that tank has an access panel? There's a reason for that. Future repairability. His tank isn't even a composite tank!
@@Zalex612 It would seem fraught with peril, as complex as it is. Either they have developed blindered to this point, or they aren't sharing their solution. I reckon the second is more likely.
Was wondering why you chose the aluminum core over the arramid core? Thanks for these videos I'm learning lots from these little bite size videos
Having gone through the stiffness/weight numbers myself I found that surprisingly enough the aluminum was superior, at least when it comes to that one supplier whose products i was looking at.
@@oddspaghetti4287 - very cool. If ya dont mind. By how much roughly?
Hey guys how do you bond those panels like how do you make a T-joint or L-joint after machining the sandwich panel.
Maybe save some of the offcuts from each panel, test each one for bending, and save in a library in case of issues with kit parts.
Evan Gatehouse Good idea
Evan, we might do a video on this down the road but in the earlier days when we were moonlighting the company all we did was R&D and destructive testing on the panels. :)
@@DarkAeroInc This was more of a post production QA test to ensure you're not shipping parts where somebody mixed the resin slightly wrong or the vacuum was too high and sucked too much of the resin out etc etc. Just to verify that the material properties are as predicted. At the high end in my world, the incoming raw materials are also tested before you build anything with it.
Agreed that quality checks are critical. We have a set of QA checks and manufacturing procedures we use that are mostly proactive but we run some destructive tests as well. In the process of developing the panels, we had to determine all the variables that contribute to making a quality panel. One thing we learned was that on a panel as large as 4'x8', there can be variation across the panel if your process is incorrect. Testing a cut off scrap is only useful if you have the correct manufacturing procedure in place to ensure consistency across the whole panel. We follow a specific procedure to manufacture the panels and document that key variables are within acceptable limits. Who would have thought making a flat panel could be so involved! :)
Awesome work guys!
Wait a minute - you say you didn't use one of the prepreg plates, because it had holes and wouldn't store fuel well - but surely you wouldn't expose a laminate directly to fuel without some sort of liner? Also, when it comes to foam/hex cores, isn't aren't the carbon and cured resins the most temperature-intolerant parts of the laminate? I thought aramid and aluminium were both more temperature resistant than carbon and epoxy.
Thank you for watching Invisty! Great questions! Laminates can be exposed directly to fuel provided that the chemistry of the epoxy used in the laminate is fuel compatible. Yes, typically the cured resin and foam cores are the limiting factor for temperature capability of a composite structure. However, there exists a wide range of epoxies and core materials that can be used which all have different temperature capability. We only use resins and core materials with temperature capability beyond 300 F. I didn't give out any specific numbers in the video but many of the 3rd party panels we tested had carbon fiber and epoxy skins with service temperature ratings of 180F and below.
@@DarkAeroInc Thanks for clarifying, my ignorance probably stems from only using composites for boats. I think the very idea of a kitset carbon panel plane to be ambitious and really cool. Hope you can pull it off with all the tricky engineering required.
When bonding a sandwich panel to the wing skins, do you add a "spar cap" or strip to interface between the edge of the panel to the wing skin. Curious about imprinting the substructure to the outer side of the wing skin.
Are you using baffles in fuel cell and wing tanks?
Looks great guys. Keep up the good work
So, no ultimate load test? Just design to 2.5x planned loads?
I hope you guys have a good factory build center because all the glue joints for the wing skins have to be perfect. This is why the commercial gliders have single spar to ease the manufacturing because they only have to worry about the main spar, the ribs, the leading edge and aft spar. Good luck though. We need to have another composite kit that follows the Lancair 360 or the Glasair 3. However, few people can afford to build them.
@2Phast4Rocket, this part of the assembly process is done on our end. The builder receives the wing fully closed out.
How do you deal with galvanic corrosion?
Interesting design. Very modern.
I am very much interested in how you plan to build the gas tanks. From what I am hearing, it sounds like you will be doing wet wings. How does that work out with ethanol fuels?
Very concise explanation! May I ask how do you join separate panels which are perpendicular to each other along the edges?
Thank you for sharing. One quick questions.
How did you handle the potential issue with galvanic corrosion?
Sì! E la corrosione?
Same Thoughts...a large helicopter manufacturer had made their tail boom panels with aluminum core... they had to redesign due to corrosion. I believe this comprised strength and caused problems.
@@jeffreygoyer7760 I would imagine the solution be either or a combination of anodizing the aluminum material, and an epoxy/fiberglass barrier. But let's see what their solution is.
The carbon fiber is electrically isolated from the honeycomb using fiberglass. The panels themselves are carbon - fiberglass - honeycomb - fiberglass - carbon.
Jim Bede would be proud
Can composite be used instead of aluminum? And which? Thank you.
How do you bond it to itself?
Is the CFC resin UV resistant?
great job guys! question, how would aviation fuel, over time, affect glue (polymer) which you use to sandwich panels with the wing skin ?
Do you soften the resin by heat for bending it?
Thanks for video. How do you join the shear webs from sandwich panels with the wing skins? Which adhesive do you use? I am concerned of an extra weight gain due to the adhesive which is absorbed by open cells of honeycomb. Also I am concerned of the joint between the skins of sandwich with the wing skin. How do you do surface prep before bonding?
How do you guys stop corrosion between the aluminum and carbon? Are you layering fiberglass between?
Awesome videos, love to see the progress!
Thanks for watching and the question! We just released a video on how we prevent galvanic corrosion on the DarkAero 1: ua-cam.com/video/yRpMZaU8zKw/v-deo.html
Awesome video as always ! Going to subscribe to the online courses very soon ! One question, I am building my own aircraft now, and I do hesitate between aluminum and aramid honeycomb for the main fuselage frames (both 0,6inch). With your experience, which one would you use? (with 2x210g carbon twill on each side of the panel, plus 50g glass each side if aluminum for galvanic corrosion prevention). Thank you so much ! Waiting for the DarkAero kit !
What method are you using to prevent Galvanic Corrosion?
Just out of curiosity. how much carbon fiber was used for the skins?
Great video! Why did you choose aluminium instead of aramid for the honeycomb layer?
How did you bond the carbon fiber sheets to the aluminum honeycomb?
Does this have to be made with prepreg? Is the surface resin all that's used to bond the honeycomb to the CFRP? I assume bonding honeycomb to sheets after the cure doesn't yield great results and adds weight from extra resin....
Beautiful design for rigidity, strength and lightweight qualities. I wonder if the aluminium honeycomb was carbon also what the qualities difference would be? Answers would be interesting! Great video, liked and subscribed!
I assume you put a ply of fiberglass between the carbon and the aluminum honeycomb to prevent galvanic corrosion?
Is it more ideal to make the wing, vertical and horizontal stabilizer a whole piece of sandwich panel? (assume the honeycomb core can be made to fit the airfoil and accommodate fuel)
what's the density tho? I'm considering using this one our launch vehicle.
Some part of me wants to build funiture using this so moving would be super easy. like a 4kg Desk or something.
I am building scinfi dioramas...where would one find the aluminum honeycomb sans sandwich?
What did you used for your ginormous fuel tanks??
Hey! I just wanted to ask how you glue or attach the carbon fiber sheets to the honeycomb core. Thanks!
Viktor, thanks for the question! We haven’t publicly disclosed that information. That’s more of a trade secret at this time.
@@DarkAeroInc Oh alright i understand, thanks for replying.
I didnt find a video from you about how to make the honycomb composite. From watching your videos, you prefer unfusion. But can that be used when you have a hoycomb with hollow space between the latyers of fiber/carbon on either end? Do do you prepare carbon panels and cure them and "glew" the carbon panels to both side of honeycomb? If you used a vaccum process, wouldn't the carbon want to go into each honeycomb hole& (and wouldn't the resin want to fill that hole if using infusion?
so, do yall sell panels now
how did you manage the problem with eletric-corosion between aluminium and carbon ?
There is a later video on that subject. They use a lightweight layer of glass between them.
Thanks for the great video. Is there a video explaining how you create your sandwich panels? If not could you make one please??
What's the fire resistance of your panels? Both carbon fiber and aluminum burn very well in air. Do you add a fire retardant into resin?
I wonder if this would be possible to apply to smaller parts, like the ones used on multirotors, which use 2.5-5mm thick carbon fiber plates.
Can that used in car body? And is can that stop a knife
Really loving how this plane is coming together. Currently on a bit of a project with an old Mooney but I could see myself in a DarkAero in a couple years. One question -- Mooney types really tout the crashworthiness benefits of the steel frame that surrounds the cockpit in those airplanes. How have you guys thought about crashworthiness in this plane?
All modern race car crash structures are made from carbon fibre - it's much better at absorbing energy than steel, and also by not having any holes like you would in a steel frame it's much better for preventing puncture injuries.
So in theory could you make a whole plane out of folded honeycomb carbon panels including all the outer skins? Is there any structural weakening when you mill and bend the panels? It would be a very boxy plane but maybe an interesting proof of concept.
The folding plane concept as been applied on several air frames in the home build community for over 15+ years. Mr. Steve Rahm was the inventor of the process, using foam core vs honeycomb aluminum.
pro-composites.com/FAP.html
Vision airplanes was one of the most ambitious design using this technique. I think they are no longer around unfortunately.
The basic concept is you can make a curve composite panel out of flat one by machining the inner layer, then bend the panel in a form, and they you re-force the areas that are cut with layers of carbon/fiberglass as to re-establish the overall strength.
The Personal Cruiser is another plane design that uses the same concept. Here is a video on the assembly process.
ua-cam.com/video/Sw7xafhj9ZI/v-deo.html
Its actually brilliant, if you can mass produce quality flat sandwich construction. The mfg & assembly process becomes repeatable and at a lower capital expenditure as they are not investing in high cost molds and dies.
For the builder its also great as you can ship parts relatively flat, therefore lowering the cost. All the while not having to form your own fuselage using traditional composite construct (Burt Rutan and such).
These guys are on to something.
Yes, the "Chipper" was manufactured this way and was boxy.
The YB-70 Valkyrie was built with an outer skin of stainless steel skins brazed to a stainless steel honeycomb. They had compound curves. They also had delamination problems.
The SR-71, designed just after the YB-70, used sheet titanium instead. Leading and trailing edges, and the inlet cones and vertical stabilizer were initially an asbestos-silicone composite, intended to be stealthy. They may have given up on that at some point.
It's amazing how long people have been using composite technology. The De Havilland Mosquito built during WWII was, in some sense, a wood/glue composite, as were some of the wackier German airplanes.
The honeycomb edges connect to the composite layers on a very small surface. How is it still a strong enough bond that can be relied on so much? How and when does it fail? It's fascinating.
Found some technical insight here: ua-cam.com/video/aL8HQtpxQqg/v-deo.html
I'm curious what the cost difference is between off the shelf panels and your own panels, and why aluminum core over an aramid core in your own panels. I'm also curious about your manufacturing method of these panels, I've only ever seen this done with pre-preg, and I know everyone has their own slight variations on how they make theirs; but I'm going to guess you manufacture, or buy, the carbon panels first, then bond them to the honeycomb, to avoid resin seeping into the honeycomb and adding dead weight, where in typical pre-preg pieces, the honeycomb is sandwiched between the sheets before bagging and curing.
Just Great , what about weight ?
4:10 The name of that technique is kerfing.
Do you use any separator material between the aluminum and the carbon composite to avoid galvanic corrosion?
Nils, thank you for watching. Yes, we have a layer of fiberglass that separates the aluminum honeycomb from the carbon fiber.
Would like to see how they bond the wing skins to those ribs?
Very interesting airplane and fabrication. Show us how you made the honeycomb panels before sending them to the router.
Weird question, can we make a chassis, body for an ae111 with this. I've got the money. Just not the time.
Kick ass. Nice video.
How do you deal with the corrosion that happens between the carbon and aluminum?
Jim, thanks for watching and the comment. The carbon fiber and aluminum honeycomb are electrically isolated using a layer of fiberglass. We have a video coming out in the future that goes into more details on galvanic corrosion so stay tuned!
I like your approach, make one big panel and cut it to make various parts, very economic👌