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While honeycomb core composites are used across aircraft interior applications for their low weight and high stiffness, efficient and consistent core splicing remains a major design challenge. This paper explores how honeycomb core splicing and finishing can be enhanced by controlling variables of the cure cycle.
While expanded foil wide area conductors have been successfully applied to fiber reinforced plastic skins for lightning strike protection, they incur a substantial weight penalty. This paper explores how very thin wide area foil conductors can help enable powerful lightning strike protection at a fraction of the weight.
Application of expanded foil-based lightning strike protection films to carbon fiber reinforced plastic aircraft skins has been attempted through automated fiber placement. However, the film material frequently has difficulty resisting dynamic forces encountered during application. This paper discusses a conductive lightning strike protection prepreg robust enough to survive AFP application.
You can streamline time-consuming processes, avoid autoclave bottlenecks and automate your applications. This free webinar explores how aerospace adhesives, engineered to meet OEM and Tier specifications, can empower you to tackle tough production challenges and enhance your process efficiency.
(DESCRIPTION) Presentation. Slides. (SPEECH) Good morning, good afternoon, or good evening, depending on where you are in the world, and welcome to today's Aviation Week webinar, Advancements in Lightning Strike Protection Technologies for Composite Aircraft Structures, sponsored by 3M. I'm Hannah Bonnett with Aviation Week and I'll be moderating today's event. We have just a few announcements before we begin. This webinar is designed to be interactive. The dock of widget at the bottom of your screen will allow you to learn about today's speakers, download resources, share this webinar via social media outlets, and participate in the Q&A session that takes place at the end of our presentation. The slides will advance automatically throughout the event, and you may also download a copy of the slides via the green resources widget. Toward the end of our webinar, we will ask you to complete a survey found on the right-hand side of your screen. Please take a minute to fill this out before leaving us today, as your feedback will provide valuable information on how we can improve future events. Lastly, if you're experiencing any technical problems, please click at the Help widget found at the bottom of your screen, or type your issue into the Q&A area and we'll be glad to offer one-on-one assistance. And now onto the presentation, Advancements in Lightning Strike Protection Technologies for Composite Aircraft Structures. Discussing today's topic are Dr. Michael Swan, senior development specialist and project manager for 3M Automotive and Aerospace Solutions Division, and Anna Geary, global new product marketing manager, Aerospace Adhesives for 3M Automotive & Aerospace Solutions Division. Anna, Mike, over to you. (DESCRIPTION) Slide, Advancements in lightning strike protection. (SPEECH) OK. Good morning, good afternoon, and good evening. Thank you for joining us for this webinar where we will be exploring advancements in lightning strike protection, where we'll been looking at exploring new technology advancements in materials for composite structures. (DESCRIPTION) Slide, Presenters. (SPEECH) So the presentation will be delivered primarily by Dr. Mike Swan online and myself, Anna Geary. Mike has been at 3M Company for 34 years, and has expertise in the fields of magnetic media, fire protection solutions, non-woven and thermal acoustic insulation technologies, RFID, and a wealth of knowledge in adhesive chemistries. For the last 17 years, Mike has had a focus on aerospace applications, primarily looking at polysulfide sealant chemistry, a broad spectrum of adhesive technologies, and latterly, lightning strike protection technologies, which we'll be discussing today. He's also a keen aviation enthusiast and a qualified commercial pilot. For myself, I've been at 3M Company for 15 years, primarily in marketing and commercial roles. And I have spent the majority of that time managing and marketing adhesive and tape technologies. And for the last 10 years, that has been focused on aerospace applications. (DESCRIPTION) Slide, Agenda. (SPEECH) So the agenda for today. I'm going to give you a whistle-stop tour of 3M Company, and then we'll move into the main body of the webinar itself. So we'll explore why lightning strike protection is important for modern aircraft, we'll look at servicing films with built-in lightning strike protection and how those can be optimized for design, processing, and quality and weight reduction. And then finally we'll end with exploring next-generation technologies in lightning strike protection and really some exciting developments in that area. (DESCRIPTION) Slide, About 3M. (SPEECH) So, 3M Company. So for those of you that don't know, we're a multinational organization. We have four large business groups where we supply products for safety and industrial solutions, so personal protective equipment, general tapes and adhesives, abrasives, and so forth. We have a transportation and electronics group, so we do electronic materials. We have an automotive and aerospace division, which Mike and I are part of. We have a health care, a big health care organization which provides solutions for oral care, for theater, medical solutions, to name but a few. And then finally we have a consumer division, and you may know us well for our post-it notes, and we also have a plethora of products for home improvement markets. (DESCRIPTION) Slide, Global Capabilities. World map. (SPEECH) So we have a very broad presence across the globe. We have sales operations in 200 countries and general operations in 70. We've got manufacturing plant facilities in 37 countries. For our aerospace division that Mike and I are from and our lightning strike protection material derives from, we have four plants, two of which are based in the US and two of which are based in Europe. But we have R&D capability worldwide, primarily in 55 countries. So we're well set up to service customer needs. (DESCRIPTION) Slide, A trusted partner with aerospace DNA. (SPEECH) And finally just a little bit about our experience in the aerospace industry. So 3M have been operating and developing products and solutions for the aerospace industry for the last 65 years. And we started out with film adhesives in the 1950s and moved on to pastes in that time and low density void fillers for honeycomb filling and so forth. More latterly, we've been developing composite resins, next generation erosion protection films, advanced liquid shims, which are required for these modern aircraft which are made primarily of composite materials, more lightweight structural bonding pastes, and then composite surfacing and lightning strike protection films, which we'll look at various points in this presentation today. (DESCRIPTION) Slide. (SPEECH) So I'll now hand over to Mike and will get into the content. Anna, thanks very much. Thank you. Pleasure to be with you today, this evening, this afternoon, wherever you are in the world. Look forward to sharing a little bit of information on lightning strike and why we want to talk about it. (DESCRIPTION) Slide. (SPEECH) So starting off here is a fairly standard statistic that on average, every aircraft is struck at once a year in the commercial fleet. Also it's safe to say there's over 8 million strikes a day that hit the Earth, that's about 100 times a second lightning's hitting the ground, and that's the small number of strikes. There's even more strikes occurring from cloud to cloud. So it's a very common natural occurrence, phenomena-- sorry-- and it's something that is bound to hit an aircraft. That does not result typically in any loss of vehicle. I think the last recorded accident in the United States was back in 1963. [COUGH] And since then the phenomena of lightning strike has been well understood and how to protect the aircraft. The traditional aircraft structures have been metal over the years. And as we transition more to composite structures, the potential for damage increases. And we'll touch on that briefly on some future slides, they're coming up. The consequence, really, today for lightning strike and the damage it can cause to aircraft is loss of revenue due to aircraft on the ground. That require inspections, potentially repairs if the damage is sufficient, and that can ultimately cause delays in departures and passenger disruption, all of which need to be avoided. (DESCRIPTION) Slide, Lightning strike zones. Diagram of aircraft. (SPEECH) So knowing that aircraft get struck pretty regularly, the FAA and other certification agencies around the world have defined how to view the aircraft. And I'm not going to get into the detail complexity of the physics here. There's much smarter people around that can explain that in more detail if you need. But suffice to say that when you look at the aircraft, you break it into zones where you are most likely to get the high current from an initial strike. So think of pointy bits or large chunks of metal. So anywhere that's highlighted here in orange are zone 1 strike areas. And those have a lot more current but have typically short detachment period. And then you move into zone 2 where the lightning will sweep across the aircraft, reattaching multiple times, typically, as the aircraft flies through the strike. And you can see this in the lower picture with multiple strike points. And then ultimately that strike leaves the aircraft at some point, typically, at the rear or trailing edges of the surfaces. And that exit point typically doesn't shift too much and protection is often provided in those areas by a static strips that stick out from the back of the trailing edges. So each of those zones requires a different degree of protection. Dealing with the high current of an initial strike requires more protection than the longer, slower burn that occurs during the zone 2 type strikes. So it's something to just keep in mind when you're looking at the different lightning strike solutions and how they might work and where they might be used on the vehicle. (DESCRIPTION) Slide, Lightning strike damage. (SPEECH) As we already alluded too, metal structures tend to not be as damaged as much as composite structures. So obviously aluminum structure itself is highly conductive. And metal, when struck by lightning, conducts the energy away from the strike point very efficiently and moves it out to the separation point on the aircraft where it leaves. Typically you'll see paint damage in the areas where the strike occurs. And depending on the intensity of the strike, anything from a small pinhole burn in the aluminum to a fairly large burn out. I've seen photographs of some fairly substantial damage on metal structures, but that's not typical. Composites on the other hand if they are unprotected will basically blow out from the attempts to transfer the energy from the strike point. The photograph down here shows an unprotected composite material with the fibers pulled out of there. So as a result of that there is a need to put some form of protection on that outer surface. And that's typically a conductor of some sort that will help minimize the damage to the structure. (DESCRIPTION) Slide, Types of lightning strike protection. (SPEECH) The typical technologies that are used in the industry today. I have the first group, which is all foil-related. You could put a continuous foil on the structure. That comes with challenges around shop handling and conformability. And I'll touch on that a little bit when I start talking about some of these other foil-based technologies. The most traditional solution in the industry today is expanded copper or aluminum foils. Basically those are materials that are cut from continuous foil by putting slots into them and then stretching the foil to create this expanded foil. We at 3M and with some other partners have been looking at perforated foils. And in this case, the technique basically involves cutting specific pattern designs that are optimized to provide performance. And again, I will be talking a lot more about that in the next section. Less common but still used are woven and interwoven conductive materials. The conductive fibers are woven in the outer layer of fabric that goes onto the structure. Typically are less effective, but certainly more efficient in terms of being able to put them on the aircraft during its build. And then and then finally conductive coatings. Those are plethora of solutions that involve spraying and applying these types of materials onto the surface. One of the biggest challenges here is, was two challenges. One is to get enough conductivity into those and the second is to know exactly how much material you have applied. Not things that can't be resolved, but definitely challenges in the use of these materials. (DESCRIPTION) Slide. (SPEECH) So this next section I'm going to talk a little bit about what I've touched on previously, which is perforated copper foils and the surfacing resin systems that are used with those. (DESCRIPTION) Slide, Lightning Strike Protection Surfacing Film System. (SPEECH) So, we really have to think of the foil solutions. And if we just think about a traditional expanded copper foil, it's a network of fibers, basically, that are joined together at nodes and you need to fill that with resin in order to get a smooth surface. So, it's important to think about the whole system. And you'll see that as we go through this slide deck that it's a combination of the resin and the conductor that provides this outer surface area onto which the paint goes. So there's a massive amount of functions that that outer layer has to perform. Obviously it's providing lightning strike protection, it needs to provide a smooth paintable surface, and then it also needs to have a bunch of secondary performance requirements. It needs to be compatible with the conductor and the underlying structure and prevent micro cracks from forming, which can allow moisture to get in and cause corrosion in the embedded foils. There's also the question of removing the paint. So those systems need to also provide resistance to chemicals used in paint stripping and just general hardness. And then, of course, in all of these solutions, they need to be repairable after damage. So I won't say there is no solutions out there today. There are very few solutions available that would result in a no-damage situation to the structure. It's a matter of how much protection you want to provide. (DESCRIPTION) Slide, Surfacing Resins. Diagram. (SPEECH) So I already maybe touched on much of the content of this slide. But the surfacing resin, while a very thin layer in the whole structure of the skin, performs a very vital function. And it's important to design the chemistry so that the cure characteristics of the resin system match those of the underlying structure that you end up with the resin being where you want it. So in the pictures you see on the side here, you can get these surface defects. This is a painted piece of skin, one surfaced badly and one surfaced well. On this side here you can very clearly see this pitting. And that often is a challenge because that pitting doesn't show up until you go to paint it or until after you've painted it. So when they're preparing the skin of the aircraft for painting, it's often sanded and prepped and any defects are filled. So if that resin system can provide a defect-free surface, then the people who are doing the painting operation can very quickly move into that operation and not be surprised by telegraphing a defect through the surface. There's also a lot of time and effort going into making sure that these surfacing materials have the appropriate shop-handling properties. You can make them too sticky or not sticky enough. They need to be able to be stored outside of the freezer for enough time. It's the first part often that goes onto a build-up, and so it is often out of the freezer for the longest of all the components used in making a structure. So you need to design these materials to have the appropriate out time. Clearly, and we're going to talk about this in all solutions in aerospace, keeping weight out of the structure is also extremely important. And I think I touched on these other items already, the chemical resistance and thermal stability, in particular during thermal cycling from the hot-cold exterior skins of the aircraft where you go from minus 65 at altitude to plus 120 Fahrenheit. (DESCRIPTION) Slide, Foil conductor configurations. (SPEECH) So I just want to explain a little more about the expanded foils versus the perforated foil. In the case of an expanded foil, as I described earlier, the foil itself is cut, so there's a slit where I'm indicating with the point of here, and then it stretched. And what you end up with are these nodes here between the slits. And if you look at the cross-section of the holes on the wires here that come from this, when you get into these node sections, you have an immense amount of copper that is essentially not doing anything electrically. You only need a constant cross-section throughout the entire network here. So there's a lot of excess copper in these nodes. And what we've been working on is designing a perforations solution that doesn't have this excess copper in the node point. So if you look at the cross section at any given point here in the perforated solution, it's constant throughout. And this is one of the ways in which we're able to take a decent amount of weight out of the solution. I should also mention that because we're not constrained by the manufacturing process as in the slip expanded foils here, we can tailor the conductivity in any direction. So in the picture here you see there's a bias in, say, this is the downward direction in this picture. There's a bias to give us more conductivity in the one direction versus the other. If you took that hexagonal pattern and made it perfectly symmetrical, you could have x and y conductivity matching each other. You'll see in most of the stuff that we're going to talk about in this presentation the conductance is designed to somewhat mirror what you currently see with an expanded copper foil. So we're deliberately designing a bias into that conductor. But that is certainly not something that is needed. (DESCRIPTION) Slide, Conductor design and impact on strike protection. (SPEECH) In this picture, it's a 2A strike zone with a 12-ply composite panel underneath it. The panel on the left is 170 gsm and that's the total weight of the conductor. And if you see the dots around here, this is where the system is grounded, and you can see the damage from the strike here. And this is a 60 gsm-- sorry, I keep using the word gsm. That's grams per square meter. This is a 60 grams per square meter foil using this hexagonal perforation, and you can see that the damage is comparably sized in the same test here. (DESCRIPTION) Slide, Thinner foil conductors are lighter. Chart. (SPEECH) An interesting consequence of not using the expanded foil technique but rather the perforation technique is not only can we get better use of the metal in it, we also can use thinner foils. And as a result of that, a lot less resin is also required. So in this pictogram on the top here, we're going from a 70 micron, or 76 micron copper used in an expanded copper foil all the way down to the other extreme where we're using a 12 micron copper foil which we're perforating. And if you look at the chart here, you can see that the cross-web and down-web conductivity of a traditional expanded copper foil, 1.6 to 4.8. And then in all the examples that we've given here, the resistance is lower in these perforated foils. So they have equivalent or better performance. And again, we're just trying to highlight here that you can flip the orientation of these foils, and so you can get your conductance in either direction. But in all cases, we meet or exceed the resistance that is currently experienced with the 76 micron foil. And as a result, a lot less resin used in there. And the table below, this section of the table shows this very clearly. You've got the conductor weight going from 142 grams per square meter all the way down to 88 grams per square meter here, and the resin content or the resin weight going from 150 down to 55. So it's a really significant overall savings in weight in the extreme examples that we've used here to demonstrate the potential for this type of solution. The transition from a very open deep type of structure, seen here on the left with the expanded copper foil, to the more streamlined perforated foil does come with a consequence, and that is that you are now starting to move more towards what the surface would consider to be a continuous foil. And copper, in particular, does not adhere particularly well to epoxy. And with the limited amount of epoxy bleeding through here, you have to start to look at surface treatments on the copper to help with the adhesion of the whole system. This is not something that can't or hasn't been resolved, but it's at least something to consider as you start to look at the perforated foils in this thinner type of configuration. (DESCRIPTION) Slide, Resin and Foil Conductor combinations can reduce weight. (SPEECH) Here we've just got a couple of examples of moving from an expanded copper foil into a perforated copper foil. A traditional 73 grams per square meter foil and 142 grams per square meter expanded copper foil are both pretty standard industry materials. And below them you can see the types of resin and ultimately the total weights of the two systems based on expanded copper foil. The numbers here underneath the perforated copper foil are what we have designed to be electrically equivalent to the 73 grams per square meter material. And you can see what we ultimately end up with is less copper, less resin, resulting in about a 20% reduction in the overall weight of the lightning strike solution. And you can extrapolate that weight-saving across the total weight of whatever vehicle you are putting that in. And that's a fairly significant number when you're looking at large aircraft. And the weight savings become even more significant when you start looking at the heavier conductors in the 142 grams range. Upwards of 26% total weight savings. So, pretty exciting technology that can really bring some amazing savings. (DESCRIPTION) Slide. (SPEECH) Just as an example of the resin systems that we're using, this is AF 536. It's a new 3M pure resin system that we're providing with these expanded-- sorry-- we're providing with these perforated copper foils. Has all of the features that we went through with the appropriate shop-handling properties, the appropriate tech. It's designed to really take the weight out of the aircraft and be easy to use on the vehicle. (DESCRIPTION) Slide, Table. (SPEECH) And the last slide in this section is just taken out of our technical data sheet, and I won't belabor the point. But we are currently offering this group of materials. We still provide that resin with expanded copper foil, but you can clearly see with these arrows here, pair that 73 grams per square meter copper with the 60 gram square meter PCF with those 20% to 26% weight savings that we have already talked about. Again, if you have any questions, specifically about that, you can reach out to either myself or Anna or anybody else at 3M. (DESCRIPTION) Slide, Automated Fiber Placement. (SPEECH) I'd like to touch now on two technologies that are more future or forward-looking. The first one is AFP or automated fiber placement. One of the challenges with putting lightning strike down today is that it's typically provided in large sheets and is applied by hand. And this is done on parts that are put together using fairly sophisticated automated equipment. So we challenged ourselves with finding a way to utilize the automated fiber placement equipment used to build parts and come up with a solution that would allow the surface itself and the lightning strike to also be put down on the same equipment. (DESCRIPTION) Slide, Automated Fibre Placement, AFP. (SPEECH) The photo on the right here shows a Coriolis automated fiber placement machine. And on the very right of this picture you can see a tool where we were running some trails. On the left you can see the green, which is our surfacing material color. And that is a fiber-placed lightning striking surfacing in the tool there. And on the next slide I'll show you a video of a spin sped up of the lightning strike being put down on this more complex tool here with compound curves associated with it. What we have demonstrated today with this is, first of all, that the material itself can go successfully through a Coriolis machine with no special treatment associated with it. It sticks well to the tool when it's applied. And from a design point of view, and I'll touch on the next slide, you can put down these individual strands to either give, I'll talk about on the next slide, but the degree of coverage that you use or get with the AFP can be varied. So, this is, if you will, the conclusion of our trials from this original. Was the second time at Coriolis. We've shown that it feeds through the system without jamming, we don't get hung up in the system, we don't see resin accumulation and any other resin in the surface, different to the resin in the primary structure, so that's a challenge that we've overcome, and that we have sufficient tack in it to stick to the tool. (DESCRIPTION) Slide, 100 gsm AFP Conductor. (SPEECH) This is a photograph of the fibers or the AFP conductive material. You can see the oriented strand type cuts here. Again, we're using the same basic principle that I talked about in the previous section, further perforated foils rather than trying to make an expanded foil here. We are perforating a deliberate pattern in here to give us the performance that we need, both electrically and mechanically. You'll notice that when you cut the edge here, we have a smooth edge to this, which helps it inside the Coriolis machine as it goes through the head. And then as I was talking about a few minutes ago, the patterning of the conductor can be tailored depending on how much protection you want from the system. You can put down a checkerboard as you can see in this photograph here, you can 100% cover it in both directions. And then you can back away from that 100% coverage and do various degrees of coverage depending on what type of protection you want. And then ultimately as you can see from this table down here, you can go from a fairly heavy solution at 200 grams all the way down to 100 gram square meter conductor. (DESCRIPTION) Slide, Automated Fibre Placement AFP in action. (SPEECH) So this is a video of the material being put down. And I'm told that it will not work in the slide deck here. So I'm going to just back out of there for a second. I'm trying and find that video. (DESCRIPTION) Clicks on play on video. (SPEECH) Hopefully you can see this OK. We've increased the speed about 5x just so that you can see the whole part being put down here. So we're doing 100% coverage, and in the minute you'll see it going into the fairly complex shape here. (DESCRIPTION) A robotic arm moves over a platform repeatedly as it does the application. (SPEECH) Works absolutely beautifully now. I'm very excited by this. So this is something we just want to make you aware of that this is based on, we'll say, a fairly traditional lightning strike solutions as you can see in this photograph here. It's a conductive foil. It's using pretty standard resin systems. So there's nothing terribly complicated about what this looks like ultimately. Obviously it was not an easy thing to accomplish, but we would be delighted to talk to anyone who has any questions on this and how this could be used to speed up production. (DESCRIPTION) Slide, Novel Conductor Concept. (SPEECH) OK. The last part of this presentation is to talk about what personally I think is one of the most amazing technologies that I've probably seen in my entire career. Something that Larry Herbert developed. And hopefully he'll be able to join us for the questions. It's basically a novel way of really looking at how you handle the energy when lightning strikes the aircraft. (DESCRIPTION) Slide, Theory. (SPEECH) You have obviously, as we discussed earlier, a lot of energy, 50,000 degrees of heat in an arc from a lightning strike. You have the sonic impulse from that as it heats the air around it, which is what we hear when we hear thunder from a lightning strike. All of those, how do we manage that energy and move it away from that strike point to minimize or even potentially eliminate the damage to the structure underneath it? (DESCRIPTION) Images appear. (SPEECH) I got a couple of pictures here. The one on the left is taken, and you'll see a video in a little bit of this, is towards the tail-end of a lightning strike on a composite panel protected with a traditional expanded copper foil. And what you're really seeing there is a concentrated burn in a single point. And effectively, the lightning is boring a hole into the structure until it separates and move to its next attachment point. On the photo on the top right, you can see some little fingers coming down from the lightning. And what we're doing here is causing the lightning to be driven across the surface. So we're controlling where the arc is attaching and how it's moving across the surface. And as a result, we can dissipate the energy over a larger area and minimize the damage. This statement at the bottom here is we're really going to some kind of a guided attachment. We want to control how and where the lightning attaches and how long it stays there for. (DESCRIPTION) Slide, Guided Attachment. Outline. (SPEECH) So the structure that's been designed to do this, and there's a photograph on the bottom left here, you can see these little hill-like features sticking up, just visible on the top of this composite layout here. And this images here from a patent show where the conductor is. It is actually a continuous foil in this case. It's a multi-layer structure that has been designed to manage the energy and increase the resistance during a strike event and I'll touch on the next slide. So the idea ultimately here is that lightning will tend to preferentially attach at these high points and then it can be moved away. And I'll explain, on the next slide, why the lightning doesn't just stay on one of those high points but continuously moves around. (DESCRIPTION) Slide, Forced Arc Movement. Diagram. (SPEECH) So, I think this is animated. Here we go, yes. So the lightning strike will attach or one of the streamers it will attach to the skin. It'll, as electricity always does, will go through the path of least resistance, which would be the top of one of these points here. As the lightning attaches, the conductor is heated. I mentioned that multi-layer structure is designed so that the resistance will start to increase dramatically. And as a resistance increases, the lightning will preferentially move to the next peak that's near it, and the same event will happen again. And then the lightning moves again. So basically you're driving the lightning around by the material properties of the conductor responding to the heat. And that cycle just repeats throughout the entire strike. Really, really very cool. (DESCRIPTION) Image. (SPEECH) That's a bit of animation here. (DESCRIPTION) Slide, Resistance. Graph. (SPEECH) What Larry has achieved here is frankly incredible. So we're looking at 10 micron thick layer of conductor in a continuous structured foil. Very low resistance, much lower than traditional expanded copper foil, certainly the lightweight copper foils, but at a comparable weight. So we're having problems with the pictures not moving. (DESCRIPTION) Slide, Strike Protection. (SPEECH) This is what I'm going to show in the video in a minute is two strikes. The panels are 10 by 10 as you can see from the description here. You'll see a lot of paint damage and charring on the surface on the novel lightning strike protection solution. On the other one, the damage is substantial and throughout the material. So on the back here, in fact, you can see the plys have been pushed out and there's been damage from the impulse from the strike as well as the burning and charring that occurs on the front side. In this example here the damage is basically non-existent other than the paint has been burnt off the top side of the lightning strike. (DESCRIPTION) Slide, Novel Conductor Concept Summary. Bullet points. Slide, Image. (SPEECH) Oops, I'm sorry. Let me go back to the previous slide there. (DESCRIPTION) Returns to previous slide. (SPEECH) So in summary, this is a novel solution. Unlike the perforated fires we talked about at the beginning of the automated fiber placement, it's a different way of protecting the aircraft, and as such, needs a different way of thinking about how it can be used. Obviously we now have a continuous foil which can provide some enhanced shielding performance. We've demonstrated that it works very effectively in the 2A strike zone area, even with nearly 400 microns of paint on it, with a conductor down at 88 grams per square meter. (DESCRIPTION) Slide, Image. (SPEECH) So, let's move on to the last slide, which is a video. And for those of you that have got to drop out of this presentation, again, here, I'm sorry about this. But for those of you who have not seen a lightning strike before, what we're doing here is looking on the top of the panel. We've got the electrode here, which is around ball. Its above the surface of the panel itself. And I will click Play here and see if it starts to work. (DESCRIPTION) Clicks play on video icon. (SPEECH) So this is a side view. This is the white painted surface. You can see a faint wire here which initiates a strike onto the surface. This is a high-speed 40,000 frames per second. And this first one is striking a panel with traditional expanded copper foil on it. And if you recall from the previous slides, what we're looking at here is essentially just a burn through in that area. This is just a short section of the whole strike because 40,000 frame per second, that would take quite a long time. But you can see by the end of it there's a hole in the structure there. (DESCRIPTION) A hole appears. Smoke rises from the contact. (SPEECH) And there's the damage, effectively burning through that outer layer. And here, we can see now all of the individual attachment points and that behavior that I described earlier. The lightning just doesn't know where it wants to attach. And so just constantly walks around the surface, like we said, taking paint off the surface but doing no damage to the underlying structure. (DESCRIPTION) A burst of light moves frenetically around the surface and lets off smoke. (SPEECH) So both those images or those high-speed images were the same strike on the same panel with the two different protections. And here you can see the damage to the surface. Basically just the paint got some slight charring on it. So, that concludes my presentation. I appreciate you spending the time to listen to us. And we're now going to open up to questions and answers. (DESCRIPTION) Slide, Questions? Logo, 3M, Science, Applied to life. Slide, Q and A. Aviation Week network knowledge center webinar, produced by Aviation week network. (SPEECH) So just before we begin today's Q&A, please direct your attention to our webinar survey available on the right of the presentation window. If you close the survey, you can reopen the widget by clicking on the clipboard icon along the bottom of your screen. And thank you so much in advance for filling out the feedback form. It really helps us serve you better for future webinars. We have had lots of questions come in about the slides and please be assured that you'll receive a personalized follow-up email with details and a link to today's presentation on Demand. But for now, let's move on to the Q&A portion of our event. As a reminder, to participate in the Q&A, just type your question into the text box located to the left of the presentation window, or click the purple Q&A icon at the bottom of your screen. I don't think we'll be able to answer all of the questions submitted today because we've had tons come in, but If not, we'll be sure to share them with our speakers so they can reply to you offline. So, Mike, one of the first questions that came in was just asking if you can expand on how the pattern can be optimized for down or cross web performance. Thank you, Hannah. Yes. Basically the hexagonal shape can be designed to give optimized conductivity where you want it. So if you imagine just a straight hexagon, you would have basically comparable behavior in all orientations. And then as you elongate that hexagon, either in the cross-web or down-web direction, you'll give preferential conductivity in the direction of the elongation. And of course which way you lay that on the path will also dictate which way that preferential conductivity goes. Hannah. We had another one asking, how do I know which copper and resin weight combination to select from my application? Thank you. Yeah, that's an interesting question. The conductor itself broadly is something that needs to be defined between the OEM and the certifying agency. Now, for a given conductor weight in traditional expanded copper foil, 3M can guide you very clearly to the appropriate perforated copper foil that would give comparable performance. So, we can certainly assist there. And then in regards to the resin itself, we can define that resin weight to give you the best surfacing performance for the conductor system that's being used. So if it's a heavier conductor, we can provide the solution with more resin in it, or if it's going on to a part that is particularly complicated and has a lot of low-pressure zones, tend to cause porosity, we can work with you to define the resin there. Hannah. Thanks, Mike. One of the attendees asked if the AFP solution is available today and how they can trial it. OK. The AFP is not a commercially-available solution today. We have materials and we'll be happy to work with anybody that's interested in looking at it. So we'll reach out to you and anyone else who's interested in that after the webinar. We have another attendee asking how PCF is made from metal foil. Yeah, I think I explained in the presentation that expanded copper foil is just stretched from slips put into copper foil. And the perforation is basically taking the same foil, but you can use multiple techniques to put those perforations in there. Traditional perforation would be a mechanical embossing of the shape and there are many other ways that that can be done. OK. Can you talk about the repairability of these various foil applications? Certainly. Expanded copper foil, as I told you, has been used extensively on composite aircraft a considerable amount of time now. And OEMs and the MROs have worked out good schemes for repairing those types of things. The perforated copper foil doesn't fundamentally change how composite structures are handled when it comes to repairing. So if you have to cut out a section and put a new piece, then you would use the same technique that you would use today for an expanded copper foil solution. One of the questions that came in said that carbon fiber and some other composites are conductive. Asking about any special protective techniques or application procedure changes. I'm sorry, could you repeat that question, Hannah? Sure. Sorry, Mike. One of the questions that came in said carbon fiber and some other composites are conductive. Any special protective techniques or application procedure changes? The short answer is no. We would not expect any changes in how that would be handled and protected. OK. One of the questions that came into said dramatic weight savings, how commercial is this product? So, yes, the perforated copper foil, I assume that was what that question was relating to, is commercially available now. We have a portfolio of offerings that we showed in the presentation and we'll be happy to share with you. So if you would like to get samples of any of those materials, they can be arranged to be shipped down. OK. We've got somebody asking if it's commercially available or in development. I think it's the same question, but, yes, commercially available for the perforated foils, the other two solutions are both in development. So the AFP, obviously we're making enough material but it is not commercially available yet. And for the last solution that we showed that we call it the advanced conductor solution at the end, that is a bit further back in development and we'll be looking to partner with somebody to drive that forward in the future. We've got a question am asking what's the recommended techniques to electrically bond between seams and panels. We would not recommend any change to the current method. Again, I'm assuming we're talking about the expanded copper foil versus the perforated copper foil. Both would be handled and managed in exactly the same way. OK. Fantastic. Well, Mike, thank you so much for taking part. And before we sign off, I'd like to thank you and Anna and our sponsors, 3M. Just a reminder that within the next 24 hours, all attendees will receive a personalized follow-up email with details and a link to today's presentation on Demand. And please feel free to invite your colleagues and peers who may not have been available to listen to the event. If you joined late or had any audio issues, that will be shared with you very soon. Thank you so much for attending and have a wonderful remainder of your day. Thank you. (DESCRIPTION) Slide, Dr. Michael Swan, Senior Development Specialist and Project Manager. 3M Automotive and Aerospace Solutions Division. Hannah Bonnett, Moderator, Events Content Director, Aviation Week Network. Anna Geary, 3M E.M.E.A. Product Manager, Aerospace Adhesives, 3M Automative and Aerospace Solutions Division
Meet your processing, quality and lightweighting targets with industry-leading LSP materials. This webinar also discusses how advanced technologies such as automatic fiber placement, novel conductor concepts and more can help you automate your processes and strengthen lightning strike protection for composite structures.