[LIVE] Guest Lecture & Coaching Clinic Research Paper Writing

Added: 2026-05-28

[00:02:51]Okay. Uh good morning ladies and gentlemen uh our distinguished lecture professor and as well as uh our fellow students.

[00:03:10]Welcome to the guest lecture uh future of combosite materials from carbon fiber to boductal composites. Before we continue, allow me to introduce myself.

[00:03:21]My name is Mohammad Rigan. I'm a mechanical engineering undergraduate student.

[00:03:29]Okay. And today I will be guiding you throughout uh today's event from the start to finish.

[00:03:39]Okay. Uh so okay. So on this uh occasion uh we are proud uh to you introduce to you we are proud uh to introduce to you for our speaker today professor Michael Robert Wisdom.

[00:04:10]Okay, Professor Michael Robert Wisdom.

[00:04:12]is a professor of uh aerospace structure who has been dedicated decades uh to the world of research and academics. He is uh also a fellow of the Royal Academy of Okay. Uh allow me to reintroduce a professor Michael Robert Wisdom.

[00:05:00]He's a professor of aerospace structure who has been dedicated decades uh to the world of research and academics. He is also a fellow of the Royal Academy of Engineering which is a distinction uh that reflects the international scientific community recognition of his outstanding contribution to the field.

[00:05:20]So uh without further ado ladies and gentlemen uh let us welcome him with a warm uh of applause uh profess professor Michael Robert Wisnom.

[00:05:36]Hello. Good morning everyone.

[00:06:02]Okay. Uh so today we're going to uh here and learn from Michael about carbon fiber composite. It's a lightweight material and it's really quite uh versatile as a structural uh material. We can use it for almost everything but it's mainly evolved from the aerospace industry and it's yeah it's lightweight and it's also strong but there are some characteristic that we can which we find interesting uh compared to metallic material and also with carbon fiber composite we have this freedom to design. I think that's the interesting key point and today we will learn from uh m Michael about the characteristic of carbon fiber composite how does it behave and also how can we predict its behavior and the tools that we can use to predict its behavior as in design it's important that we can predict the behavior so I would like to give the spotlight to Michael to give the presentation and then we can continue with the discussion if you or you have any question you're more than welcome Thank you very much Dr. Pu. It's a real pleasure to be here to tell you something about carbon fiber but also to learn about your very interesting country and culture.

[00:07:35]So on Monday we went to Garuda maintenance and I was very surprised at the beginning of the meeting there was a poem. This is something you'd never have in England. Very interesting. In England, we have a special type of poem called a limick, which is a rhyming poem. So, this is my attempt at merging Indonesian and British culture.

[00:08:02]I came from Bristol to Surabaya to tell you more about carbon fiber to inspire you in your search how to do worldleading research and take your knowledge even higher.

[00:08:15]So I'd like to now tell you a little bit about Bristol and what we do and then move on tell you about carbon fiber.

[00:08:24]So Bristol University it's is a top ranking university and we're involved in Bristol composites institute in education obviously from undergraduate but we have mast's programs and PhD programs and we're involved in research also we have a number of spinout companies and uh involved very much with research and innovation and working with industry and we aspire to be a worldleading institute for composite research and education addressing the overarching challenges of sustainability and net zero. So just a few figures, we have uh a lot of academic staff. We have more than 30 faculty dedicated to composite materials and then we have other faculty throughout the engineering and science departments working on composites and liazing with us. We have a a lot of facilities. We have investment in equipment. We produce good research papers and we have a number of our academics featured in the top uh scientist lists. Just to mention our post-graduate programs, we have a master's course in advanced composites and I was very pleased uh when visiting Garuda maintenance to meet one of our graduates who's now working at Garuda.

[00:09:45]We also have a PhD in aerospace engineering which is a traditional PhD which in the UK is mainly by research but we also have doctoral training centers. These are cohort-based PhD programs where we have a group PhD students who do courses as well as a research project and some of those are based in industry and they they do more industrially oriented projects and receive an engineering doctorate an ND rather than a PhD.

[00:10:19]We have a number of of of key partnerships particularly mentioned we have a university technology center with Rolls-Royce which is a quite a big activity working closely to help them to understand and design better composite structures and we're also working with Vestus wind turbines a large program on looking at carbon fiber in wind turbine blades number of other collaborations with other universities both in the UK and internationally.

[00:10:51]Our research priorities cover quite a wide range. Advanced engineering for net zero. We look at numerical tools to help design materials and structures. We look at novel structural and material configurations and uh highfidelity experimentation to understand behavior and working on new applications.

[00:11:16]Manufacturing is very important. And we work on manufacturing both in terms of developing new processes but also in modeling uh processes so that we can get better manufacturing processes right first time and reduce the amount of experimentation necessary to get good products.

[00:11:35]Sustainability is an important theme.

[00:11:38]Recyclable materials is is important.

[00:11:41]Low energy manufacturing processes.

[00:11:44]designing structures so they can be disassembled, easily repaired, reused and also looking at at life cycle analysis to understand the implications in terms of carbon emissions uh of the the structures.

[00:12:01]We're very involved in in digital work in applying digital techniques, software engineering using data and that links into machine learning, artificial intelligence. We recently had in Bristol the first international conference on artificial intelligence in composite materials and then we developed new materials. So we have materials at the moment which are being on trial in in space on the space station and we we developed materials for high temperatures for low temperatures and uh high temperature ceramic matrix composites and many other types of materials.

[00:12:40]Another key thing in Bristol is we have national composite center which is it's owned by the university but it's an independent it's really a it's a technology innovation center. So it's designed to take research and new ideas and then translate them into industry by demonstrating and scaling up the technology working with a whole range of industrial partners.

[00:13:07]Okay, so that's a little bit of brief background of what's going on in Bristol. It's a very large activity. NCC has about 450 people. We have about 250 people in Bristol Composite Institute.

[00:13:18]So that's about there's about 700 people working on composites in Bristol with one of the the biggest research activities anywhere in composites.

[00:13:27]So now we'll change gear and we'll talk about composites. Let's start at the very beginning. What is a composite?

[00:13:35]So you can define a composite as a combination of materials which together give better properties than they would on their own. And in this context we're talking about strong fibers particularly carbon but also glass and other materials and uh with a a matrix which is usually in this case we begin to talk about plastic matrices typically epoxy. There are other types of composites which may have metal or ceramic matrices which are particularly good for high temperatures.

[00:14:07]But here I'm going to talk about lower temperature applications which are used in aerospace and other industries.

[00:14:15]And these are made into a unidirectional material fibers in one direction. And then these can be layered in different directions to produce a laminate which has got strength in in different directions. And by putting different amounts of material in the different directions, you can tailor the properties to carry the loads that you've got in your particular application.

[00:14:39]So carbon fiber is extremely strong. It has strength up to about seven gigapascals.

[00:14:46]That's 700 kilograms uh per millime squared. So that's almost one ton on one square millimeter. So you just imagine that that's a very very strong and that's about 30 times stronger than mild steel. So it's very very strong material. It's also stiffer than steel and it's very very light one the density of steel. So you can see from those characteristics its specific strength is extremely high. So that's what makes it a very attractive material.

[00:15:18]However, it is brittle and that's a problem and I will talk about that in the lecture I'm going to give on Monday.

[00:15:23]How to overcome that and also it needs support in compression. You look at this this uh roll of of carbon fiber. You can't really see what it's like but it's very very fine fluffy fiber. The diameter of carbon fibers is about a tenth of the diameter of a human hair. So very very small. And you you look at that and you think, how could you build an aircraft from that? Because it's just it just doesn't take any load at all in compression. But when it's combined with a matrix, then those fibers because they're very stiff and strong, they're able to carry a lot of load.

[00:16:02]It is however difficult to transfer load into the fibers and that's another function of the matrix to allow loads to get to be transferred into those fibers.

[00:16:11]So carbon fiber composites were invented in the UK. Well, there was more or less simultaneously in Japan and the US and and UK, but the really early work uh I would argue was done in the UK. It's now commercialized worldwide. That really started in the60s, but composites are older than that. They're very much older. And one early reference to composites comes from the Bible from the early use of composites in Egypt. And one of the verses in the Bible says how Pharaoh commanded the task masters of the people and their four men who shall no longer give people straw to make bricks. So they used to make composites from mud and straw. The straw is the fiber, the mud is the matrix and that provides a strong material even several thousand years ago. But but actually composites are much older even than that because plants are fiber reinforced composites. If you look at uh fibers from from if you look at uh plants such as flax or hemp, then they are made of fiber bundles and they are fiber reinforced composites. And in fact, you can extract the fibers to make natural fiber composites. And that's quite a growth area because it's it's a natural sustainable material and it can be grown anywhere. And I understand there's quite a lot of work in Indonesia on these materials. So plants are fibers and there many other applications. Wood is is a is a composite and bamboo also.

[00:17:48]Bamboo is a fascinating material. Um you see in this picture on the left that uh there's a graded structure through the thickness. They're hollow. You have the graded structure and the fibers actually get more uh higher volume fraction of fibers towards the outside to give improved bending strength and stiffness.

[00:18:08]So they're a fascinating uh composite material.

[00:18:13]So what are some of the advantages of composites? Composites have very high strength, very high stiffness and that gives large weight savings. There's no problems with corrosion. They don't suffer from fatigue. Uh and you can tailor the properties by varying the layout. But the behavior is very complex and difficult to understand and to predict. And that's been a lot of my work is to understand how composites fail. And I've just finished writing this book which will be coming out very shortly on failure mechanisms in composites to really help to understand how and why composites fail uh in order to be able to use them better in different applications.

[00:18:54]So how do composites fail? Well, they fail in different mechanisms depending on the loading.

[00:19:02]So in tension then they are brittle normally and the the failure is controlled by the brittle failure of the of the fibers. In compression it's controlled by stability. Again you get a brittle failure but it's it's controlled actually by the stability rather than by the strength.

[00:19:24]And the transverse failure, you can also have separation and they're rather weak in the transverse direction because you're just relying on the matrix to carry the load. And since the matrix is not very strong compared to the fibers, then that is a potential weakness. And whilst you can laminate a composite to get different properties in the plane through the thickness, you've got that weak matrix layer. So the delamination and the through thickness failure is a critical issue composites and one of the most difficult ones to uh address and one which has caused the most problem and when there have been failures in composite structures it's usually due to that delamination. When Boeing introduced the the 787 airliner which is all composite I'll tell you a bit about that later. That's one of the problems they had with some delamination failures.

[00:20:19]So let's just view some of the properties and the different types of of loading and just tell you a little bit about how they behave.

[00:20:29]So in tension they're elastic there's no plasticity they're elastic to failure and this shows stress drain curve in tension and in compression and one of the interesting thing is they're fairly linear but there's a slight stiffening in tension and in compression there's a there's a softening and that softening can be quite quite big quite a reduction in stiffness at high strains and compression when they do fail it's sudden and catastrophic And in tension, it's controlled by the strength of the fibers. The fibers are very strong, but they're also very variable.

[00:21:05]And what matters is when you get a cluster of weak fibers together, they can interact and join up and precipitate failure of the whole structure. So you get an increasing number of fiber breaks as you increase the load. And then at a certain point, you've got enough fiber brakes that you get a catastrophic failure.

[00:21:26]So the failure looks like the picture in the top. Fairly clean break.

[00:21:33]But if you look at it under the microscope, you'll see clusters of broken fibers. You see some fibers here broken. And at higher magnification, you'll see that there's areas where we got a number of broken fibers here, but then they're also connected by splits because in this direction, transverse the fibers, it's very weak. So when you get these fibers then they can split and these failure can join up uh to create failure surface for the whole thing to fail.

[00:22:04]You can also in some materials you can get a a a brush like failure which is it's still pretty sudden but it's a bit more it's not quite as brittle as the one I just showed. And this is normally associated with a a weaker matrix or a weaker interface between the fibers in the matrix and also with higher strain fillets. So this is a glass fiber epoxy composite. Glass has got much lower modulus and much higher failure strain carbon and tends to give this more brushlike failure.

[00:22:38]So tensile failure is controlled by the strength of the fibers and is is very good. compressive failure is more difficult and is usually much lower than the tensile strength.

[00:22:50]So the fibers themselves are actually very strong. The problem is you just imagine these tiny fibers. They they they can't really carry a load without buckling.

[00:23:02]So the strength of the individual fibers been measured up to about 4 gigapascals with a 15% failure strain. Those are very high numbers. But those numbers are not achieved in composites. And the reason for that is because the failure is controlled by stability and not by strength.

[00:23:23]So it's usually referred to as microbuckling, but it shouldn't be confused with with oiler buckling. So engineers are normally more familiar with with stand traditional buckling, oiler buckling, which is a structural phenomenon. But this is actually instability and it's due to lack of support from the matrix. But it leads to a brittle and catastrophic failure and the failure is typically at an angle. In this case here, there's an angle across the width and an angle through the thickness which is characteristic of a compressor failure in composite.

[00:24:02]So the shear instability mechanism can be illustrated in this picture here. The fibers are not perfectly straight. So inevitably you have a little bit of of winess or misalignment in the fibers and then when you put them under compression that because of the angle if you resolve the stresses then you will get shear and that shear in the matrix the matrix is not stiff enough to resist that shear then that will lead to more rotation more shear at a certain point that mechanism can become unstable and it leads to collapse and you get an increase in the in the bending and then the fibers break in bending and you get a a kink band as it's called propagating across the across the specimen.

[00:24:51]And you can see an example of this from this nice microraph where you see here we've got some some buckled fibers here and here that it because of this angle this is we've got large shear stresses and then at a certain point that bending becomes such that you start to break the fibers up here and and starting to break down here and that will produce kink band which under the microscope you can see those fibers misaligned like But globally, macroscopically it looks like a crack actually from a design point of view can be treated like a crack propagating through the material.

[00:25:33]So transverse tensile failure in most cases composites are brittle and they fail with a a sudden failure at a relatively low stress and it's very dominated by the matrix and there's a lot of scatter typically.

[00:25:52]So you're just relying on on the matrix to carry the load. Macroscopically you see a a fairly clean break. But if you look under the microscope you'll see how we get debonds starting at the fiber matrix interface and then propagating through the matrix to form a crack.

[00:26:12]So it's really controlled by the the matrix and also you need to have a good bond between the fibers and the matrix because this otherwise this debonding may occur quite poorly.

[00:26:25]So delamination is really crucial. um it's caused by these high inter laminina stresses and the low through thickness strength because you're relying on the matrix.

[00:26:40]So you can have fibers in the plane to carry the different inplane loads but you don't normally have fibers through the thickness. There are some types of composites where fibers are introduced through thickness and these tend to have better behavior in delamination but not such good performance in the plane and usually the inplane loads dominate. So these laminated composites are very good for most cases but you have to be very careful with the design because if there are areas where you have high through thickness stresses then you may get unexpected failures.

[00:27:17]So let's look at some causes or some features which cause damination. The delamination is due to the high interlamina stresses weak matrix and the low fracture toughness of the matrix and it can initiate premature failure even under inplane loading and so it's something to be very careful about. So there are several different sources of these interam stresses. Clearly you can have features in the design which actually apply out of plane loading. So if you have a um feature like this a bracket and you apply a load like that that is producing a load out of plane of that laminate that produces a direct in this case tensile and sheer stress through the thickness. So that sort of feature is quite often used. composite widely used for yacht masts and you may have a a bracket in there to attach to a rigging and that produces an interlam load directly which can be can lead to failure. other features such as in this stiffened structure. This could be a wing skin and a a rib or spar and you may have pull-off loads due to fuel pressure loading and that again produces direct through thickness loading which there are in this part here there are no fibers to take that loading. So that can lead to matrix failure and delamination.

[00:28:43]But there are also features which are special about composites and weren't understood in the very early days but now much better understood because you actually have discontinuities in the material and these discontinuities can lead to very high local stresses theoretically singular stresses going to infinity uh which can provoke damination.

[00:29:05]So, one example is if you have a tapered laminate and you to taper the laminate, they're normally made from plies and you would drop off a ply. You'd stop this ply here, but at the end of that ply drop, you have a a very high localized stress because all the load that's in that middle ply there has to come out into the other plies. So, you have a very high local shear stress and that type of feature can lead to delamination. We've done a lot of work on designing these to to reduce the risk of delamination particularly under fatigue loading.

[00:29:39]Another feature which is very special to composites is the edge effect. So if you have a laminate like this n laminate here then at the free edge you have a very special state of stress because uh the in the laminate you have stresses in both directions but when you get to the free edge you can't have any stresses normal to the edge so that gives rise to inter laminate stresses and they can be very high. So this plot here comes from one of the famous early papers on composites which shows how the inter laminina stresses build up near the edge. So away from the edge of a this is a crossly laminate away from the edge there's no interlaminal stresses. If you just load it in the plane there's no through thickness stresses but as you get near the edge then you get these very high stresses and theoretically they go to infinity. Of course, in reality, they're not infinite, but they're still very high, and this can cause them to delaminate from the edge.

[00:30:39]So, these stress discontinuities and also the loading in either case can provoke damination and can be a major form of failure. And most of the failures that have occurred in composite structures have been because of this type of failure. It's relatively straightforward to design your structure with enough fibers in the different directions to take loads, but it's quite easy to to get through thickness stresses because of local design features or other issues which can give rise to these delamination failures which may greatly reduce the strength of the structure. So delamination is often referred to the Achilles heel of composites because it it's a real danger and people are used to working with metals and they convert to composites.

[00:31:24]This is the most important thing to worry about because it is very different behavior here than what you get in metals.

[00:31:33]So delamination often leads to premature failure. It destroys the ability to transfer the loads between the plies.

[00:31:41]Therefore, it can give rise to buckling.

[00:31:43]If you got compressive loads, you have delamination. It's able to buckle and fail and therefore greatly reducing the compressive strength. But it also a very interesting mechanism. It's an alternative way to to shed the load and allow separation without breaking fibers. So if you have this laminate here which is a 45 minus 45 laminate and you load that in tension then you can get these matrix dominated failures weak failures joined up by delamination which will allow that component to separate without breaking the fibers. So although you got very stiff and strong fibers, with this mechanism, it can actually fail without having to break those fibers. And structures are very good at finding the lowest energy route to failure. And if there is a weak root somewhere, the structure will find it.

[00:32:33]You'll get a premature failure. And even if you have fibers in the in the loading direction as well, you may still get this type of behavior occurs in the offaxis flies which may then put the load additional load onto the the fibers and cause earlier failure than you would otherwise get. So this is very important in structural behavior especially for impact and compression after impact.

[00:33:00]I'll show you something about that in a second.

[00:33:04]Not failure is very important because usually you put holes in structures but actually that's a very bad thing to do with composites because composites are notch sensitive.

[00:33:15]So if you have a with metals if you have a ductile metal like aluminum then if you put a hole in it then and you load it in tension then you'll get plasticity around the hole and you won't see a large reduction in tensile strength. You may see some problems in fatigue, but tensile strength will not be greatly effective. You put a hole in the composite, you get quite a big reduction in strength. So composites tend to be more designed based on static loading rather than fatigue. Whereas metals, it's very often it's the fatigue that causes the main problem.

[00:33:53]So there's very complex mechanisms at these notches. We've done a lot of work to understand it. uh won't go into too much detail but what happens is you get splits in the different fiber directions and these splits join up by the delamination as I was talking about previously and this allows a damage zone to propagate from the notch and then eventually can pull out just leaving these ligaments of of the zero degree fibers and during this process at some point the fibers will break and it the failure you get depends on when those fibers break in relation to when these other damage modes happen. So we had a big program on looking at scaling effects to understand what happens as you change the sizes, the dimensions, the thicknesses of the plies and to understand the different failure modes.

[00:34:42]And you can see in this picture here we get three very different types of failure. So the top one is a is a brittle failure just straight across the the width of the specimen. And that has occurred because there's little splitting or delamination has occurred before the fibers break. And that you tend to get that with large holes and also with with thin or dispersed plies.

[00:35:09]When you have smaller holes, then you can get more pull out here. So you can see more damage. You can see there delamination and pull out and a um a more gradual failure. And if you have very small holes or you have thick block supplies then it becomes delamination dominated and in this case here you can get complete delamination of the whole specimen and then the fibers may fail later. So very different failure modes depending on the different parameters and we've done work to really understand this and see how to predict that and how to design structures which fail the way you want them to.

[00:35:48]Now impact really is very crucial for composites and uh the damage under impact is really significant. It's probably the most important thing.

[00:35:58]Delamination I would argue is the most important design issue for composites but in the industry people normally think about compression after impact as being the most concern but actually that's because you get delamination under impact. So what happens when you this this is the the thickness of a laminate which has been impacted in this direction. Surface looks absolutely fine. If you looked at this from the outside, you wouldn't see any damage, but inside this these black lines here, a whole series of delaminations. It's delaminated between every ply in this laminate. So, it looks perfect on the outside, but you put that into compression and because of those delaminations, those sublaminates are going to buckle and you're going to get an early failure. So you could have a reduction of factor of three or or more in in compressive strength but actually it looks fine. So that's a real problem for design because anything that you can't see you have to assume the damage is there. So you have to design the structure on the basis that it includes those delaminations that you can't see.

[00:37:02]That produces quite a large knockdown means you can't use the composite right up to its full strength because you have to be aware of this possibility.

[00:37:14]So impact damage can be caused by all sorts of things. Low velocity events such as drop tools, um things being rammed or or accidents where a truck drives into a aircraft structure. But you can also get high velocity impacts such as this uh bird strike. That's a critical thing for aircraft fan blades.

[00:37:35]We've done a lot of work at Bristol on that, working with Rolls-Royce on looking at fan blades and um this can cause this delamination damage but at higher velocities and higher energies this can actually break the structure.

[00:37:47]So in case of fan blades it's not so for small uh impacts then there's a concern about delamination but for a very large bird then it can do a lot of damage. We saw at Garuda on Monday we saw a nose cone from a 737 which had been hit by a bird and it was incredible how much damage there was on the front of the aircraft. a bird, a large one, flying at a few hundred miles an hour. Well, of course, it's the aircraft flying a few hundred miles an hour on the bird, but the relative velocity is high. There's a lot of momentum and it can do a lot of damage. And so, the fan blades have to be designed so they can take that bird strike without breaking the blade.

[00:38:34]So we've done a lot of fundamental research studying this impact using just static indentation because it's much more controlled. We can stop the test.

[00:38:42]We can look at the damage, understand how it grows and model it and and it actually is very similar under static loading compared to under impact. And so what we see is behavior like this. We have a rectangular plate here on a window and then we indent it with a hemispherical indenttor. So initially nothing happens and when we X-ray or C scan the specimen at this point A there's no damage but then you see a little load drop and that load drop there what's happened is you've got delamination and these colors show the delamination the different plies and in this case we got about 14 mm of delamination at that point there. So it still can carry the load and it looks fine. And at that point there you probably wouldn't see very much damage but it would have had a significant reduction in its compressor strength. Then you could load it up and as you load it that delamination grows.

[00:39:36]So here we got about 40 mm of delamination at this point here and then we start to get fiber failures and fiber failures then would lead eventually to penetration of the structure.

[00:39:50]So the sequence of damage is transverse ply failure due to shear stresses around the periphery of the contact area and then you get these angled cracks in off-axis plies. So you can see here you've got cracks at about 45 degrees due to shear this indenttor and then when you got sufficient energy the delaminations propagate and you get this staircase pattern where you get matrix cracks in the weak direction in each of the plies joined up by these delaminations and that produces the sort of damage I showed on that previous plot.

[00:40:26]If you have enough enough energy, then you can get failure.

[00:40:31]And the mechanism called shear plugging, which uh is something we're looking at at the moment. We're working with Rolls-Royce on the design of a a new casing to resist. So I said with the fan blade, I said that the fan blade has to withstand the bird strike without failing. So that is a design requirement for the blade. But nevertheless, you also have to design the engine. So even if the blade does fail, which it's not supposed to, then it's contained in the engine. So, the engine casing is designed to take the loads of a blade as it comes off. And so, we're looking at making carbon fiber or hybrid composite casings to resist that that fan blade.

[00:41:14]Worst cases with a metal fan blade, actually, it's a bit easier with a composite fan blade because they're much lighter. So the mechanism here is you get a high zone of shear and then you get a failure which propagates through the thickness and produces this referred to as a shear plugging failure. So that's what we don't want to happen when a a blade hits the fan casing at high speed.

[00:41:38]So that's a bit about the failure of composites. Most of my research has been over many years has been related to that and I think it's it's very interesting and uh quite complex and difficult to understand but that's why there's been fairly slow progress and conservativism in using composites because we have to make sure that they don't fail and that requires that requires good design a lot of testing but increasingly we're developing models to allow us to be able to predict the behavior. so they can be used more efficiently.

[00:42:12]So composites are great materials, very strong, stiff, very very good structural materials and they have a big part to play in reducing energy and reducing emissions. So they have a contribution to reaching the net zero target which is a lot of emphasis in the UK these days and many countries on uh on reducing emissions. So composants are light so lightweight leads to reduce energy consumption in vehicles. This uh BMW car body is very light helps to reduce the the uh uh the the fuel or electric consumption and also durability of composites leads to longer life and therefore we use structures for longer and we don't need so many replacements.

[00:42:59]Lighter car bodies can give rise to smaller batteries or smaller engines for the same performance which cut emissions not just CO2 but other emissions and in aircraft we have a big reduction in fuel consumption. So whilst composites themselves have a energy and CO2 required to make them that is absolutely dwarfed by the savings in fuel consumption in aircraft. So that's been a big driver for companies to move to to using composites in aircraft structures.

[00:43:35]Hydrogen storage tanks is another big application which is receiving a lot of attention at the moment. much work going on looking at hydrogen economy and um tanks, high-pressure tanks or or alternatively cryogenic tanks to store liquid hydrogen and renewable energy wind turbines is another big application which we've been involved with and carbon fiber is really enabling much much better and bigger wind turbines.

[00:44:04]So with wind turbines the longer blades can extract more energy from the wind.

[00:44:10]So they become more efficient and can take more power the bigger they get. So over the years the size of the the blades has been getting bigger and bigger and bigger and that's been driven by this requirement to produce energy.

[00:44:24]The blades need to be light and also they need to be stiff. When they get very large then deflections of the blades can be problematic and they can hit the towers. So early blades were mainly well I think the early ones were probably Glass fiber was used in the early blades. Glass fiber is a good material, but it's not very stiff. So, as the blades got bigger, carbon was introduced. Now, with the very big blades, they have a lot of carbon in them.

[00:44:52]So, blades get bigger and bigger. Um, this is a picture here of a blade compared with a Airbus A380.

[00:45:13]Yeah, this this is quite a small blade um which is the size of an A380, but uh um the the largest are now over 150 m long each blade and that's double the span of a 747.

[00:45:28]And you can see the comparison of the the blades with respect to some of these big structures here. So they're getting really big and that makes them quite difficult to manipulate. This is this is a relatively small blade, but you can see from the the size of the trucks on the road that actually taking it around is quite quite an issue.

[00:45:47]It's good application for carbon fiber to be able to make those very long blades stiff enough to behave well.

[00:45:55]Propeller blades is another good application.

[00:45:58]So in this case here the carbon is used to to stiffen the the spars to take the bending loads. So you have blocks of unidirectional composite in the the spars here and then you have a foam core and then there's they're wrapped on the outside with angle pliers plus or minus 45. So plusus 45 plies are very good for taking shear. So if you want to resist torsion in the blade then you can tailor it. So you have the 45 plies to take the torsion and the UD plies to take the bending.

[00:46:33]This is the Rolls-Royce ultraan engine, biggest aircraft engine that's been run.

[00:46:38]Um ran about a year or more ago. And this has got carbon fiber blades. We were very involved in the development of those blades and also has a carbon fiber casing as well to resist the fan blade off case. So that's very good application, big weight saving. The blades save a lot of weight, but because the blades are much lighter, uh the casing is is has a big reduction in weight casing because it doesn't have such a large mass contain if one of these blades comes off.

[00:47:16]Space vehicle trust structures good application for composites. So we did some work quite some years ago now on the Skylon single stage to orbit space vehicle. And this shows a picture of some of the truss structure on that vehicle. So these were carbon fiber tubes to to make the trusses and then they had this these nodes to transfer the load and they were designed to be titanium. We developed some carbon fiber um joints to take the loads to connect them together and save further weight.

[00:47:52]been increasing use of composites in the aircraft industry. This plot here shows how things have evolved with Airbus. So the A300 was the first Airbus aircraft back in 1970 odd and that had a small amount of carbon fiber about 5% but every successive Airbus has had more carbon fiber right up to this recent Airbus A350 XWB which is essentially all carbon fiber structure. does have a bit of metal in it, but it's 53% by by weight carbon fiber and by volume it's even more than that.

[00:48:29]So to see where it's used, this is a picture of the use on the A320. So in the in the early Airbus, it was just used on some of the the training edge structure. The A320 uses it again uses it on the training edge structure on the necessels of the engines, but also on the vertical and horizontal stabilizer.

[00:48:50]Then the ray dome here is an aramid composite. These red ones are the carbon fiber and the fairings here in blue which are glass fiber. So that was the usage on the A320.

[00:49:05]On when they went to the A340 they introduced a carbon fiber pressure vessel pressure bulkhead at the back and also some keel beams down here. And then on the A380 the whole wing box was carbon fiber and the whole of the rear fuselage was carbon fiber as well and then the A350 basically everything is carbon fiber. So it's been a progressive implementation of more and more carbon over the development of the aircraft.

[00:49:36]So that's the civil aircraft but the A400M military transport aircraft was the first large aircraft with a carbon fiber wing. So that aircraft flew um it it it flew I'm pretty sure I'm right in saying this it flew just before the 787. So uh um so that that wing was developed in Bristol. We were involved with that work and actually that wing was fabricated in Bristol and then the final assembly of the aircraft is in Seville. So that had all carbon fiber wing but the rest of the structure is is metal.

[00:50:15]So the 787 is the first large uh civil aircraft with and first large aircraft which all carbon fiber and blue here shows the carbon fiber. You see basically all of it is f carbon fiber.

[00:50:29]There's some fiberglass for these fairings which are not so highly loaded but it's basically all carbon fiber. So here you see how the the nose cone is made. It's made by a fiber placement technique. So the mandrel And the tapes are wound around the mandrel to build up the whole structure in one piece. And then after that's made, it's machined.

[00:50:52]The the doors, the window areas are machined out and then it's assembled into the aircraft. And that's uh that's a that's a different technology from what Airbus use. Boeing make the whole fuselage segments in one go. Airbus make separate panels join them together.

[00:51:11]So you look at the some of the structures on the A350. So this is shows the fuse structure all carbon fiber that's made in four panels which are joined together and then you have a carbon fiber floor structure here and then that shows one of the wing skins which is um carbon fiber skins with these stiffeners integrated into it.

[00:51:33]So that shows some of the aircraft applications.

[00:51:37]Finance element analysis is is a great tool and we do a lot of work with that to design the structures and to understand how they fail and finance element analysis can be applied at all sorts of different levels. It can be applied at the structural level to look at the whole aircraft design. It can be applied at a stiffened panel. This is a stiffened panel with a notch here to look at how that notch propagates or right down here some very highly detailed analysis of notches in these panels and how the detailed damage progresses to help us design the materials and the notch geometry to take those.

[00:52:18]But composites have got a lot of flexibility. You can have completely different architectures. These are shown some of the architectures from my my previous colleague P who looked at making composites with very interesting microructures. And each of here this is the reinforcing on this itself is a composite. You can the individual fibers in this and then this was infiltrated in this case with a metal. So very different microructures you can get. You can tailor that structure to give you particular properties.

[00:52:48]We also made different shaped fibers in Bristol. We made hollow fibers. We made triangular and star- shaped fibers.

[00:52:55]These allowed us to change the characteristics of the materials.

[00:53:00]And another key benefit of composites is that you can make them multifunctional.

[00:53:04]You can add capability beyond just their good structural performance. So you can make them to have self repair, self-healing capabilities. You can have self cooling by introducing channels, putting liquid through them. You can use health monitoring or you can increase electromagnetic function. So this is a a structure which was made with incorporating some iron wires strips in the layout. So this has got as well as the structural functionality.

[00:53:35]It's got electromagnetic functionality.

[00:53:38]This shows some of the the bleeding composites for the self repair and visualization of damage. So, we put these little channels in there and you can put either a healing fluid. So, when the thing gets broken, the healing fluid gets out and sets and repairs the damage or you can put a dye in there so it seeps out and you can see the damage and you can know that it's been damaged even though it may be difficult to detect it otherwise. as I was talking about earlier may have internal damage which may not be visible but here with this dye included you can produce more easily damaged easily visualized damage and composites really allow many exciting new concepts to be realized for example morphing wings that change shape I was interested to hear work going on here on morphing structures and uh this enables you to make really exciting different structures and really I would say that composites are the future structures.

[00:54:39]So in summary, carbon fiber composes have outstanding mechanical properties.

[00:54:44]They enable structures to be created that simply couldn't be made otherwise.

[00:54:48]They can be tailored to specific applications and they enable multiunctionality beyond just the structural performance.

[00:54:57]So composites are underpinning the transition to green energy and would argue that they really are the materials of the future. Thank you very much.

[00:55:19]>> All right. Um, thank you very much, Professor Wisdom, for the incredibly enriching um, insights. Um, before we continue, please let me introduce myself one more time. My name is Pasha. Today I'll be swapping Egg's position for the rest of the day. All right. Um moving on to the next session. We have question and answer session. For those um of you guys who have a question, please kindly raise your hand and ask the question to professor Wnner. So um the question and answer session will be run for approximately for about 30 minutes. So any of you have have the question please raise your hand first >> or any of you uh who has been working with composite or fiber stuff who would like to share your work you're welcome and then we can have a discussion postgraduate student and gr and lecturers I know that some of you have been working with carbon fiber Uh good morning. Thank you for this opportunity. Let me introduce myself first. I'm bias. I'm from mechanical engineering. So uh before this like uh best selector right I I I took a chance at like watching a video on YouTube on like how carbon fiber carbon fiber parts are manufactured for a small part anyways like a car bonet or like an engine cover. So it's really my question is about uh the manufacturing of the carbon fiber parts itself. So I have two questions. The first one is like how would you manufacture like a large part like an entire uh airplane Q sauce like the A350 for example because from what I've seen uh you need like a mold for the carbon fiber where you will lay the carbon fiber onto part onto the mold itself and then you need to vacuum back the entire thing and then you use the uh the epoxy resin itself.

[00:57:28]So how would you do that for a large part like entire fus or an entire wing?

[00:57:34]And second question is uh uh a lot of the process that I see involves a lot of uh hands-on approach like you need to play lay out the uh the carbon fiber itself. you need to uh cut the uh the cloth itself and then place it on the mold and it just involves like a lot of uh human work or human labor for uh say uh so do we ever see like a uh a fully automated uh carbon fiber part manufacturing in the future or is it just simply impossible due to the nature of how carbon fiber is?

[00:58:13]I that's my question. Thank you.

[00:58:17]>> So very uh very good questions and actually you partly answered it yourself in terms of how the the uh um how the aircraft are made exactly as you said large mold and then lay up on the mold backing bag and then cured and autoclave. So that's that's a traditional way. If you go to the early days of composites there's a lot of manual production. So people things up by hand and a lot of manual labor but uh there's been a lot of effort to increase the automation. So most of the the the large parts so so the aircraft parts use the this automated fiber placement technique. So both and Airbus use the AFP as they call it and that involves a robot with a head which moves over the structure laying down tones of material.

[00:59:13]If you have a flat structure you can lay quite wide tapes with a an automatic tape layer but for more complex geometry you need separate narrow toes and those are used with this automated fiber placement. So that can make quite complex geometry so long as it's fairly flat. So when you have more highly shaped parts, then it's a bit more difficult to use that. So it's a bit more of a challenge for the the uh the fan blades. The fan blades I showed you probably couldn't see very much about the geometry, but it is quite complex because the fan blade is twisted. It's curved. It's twisted along. It's quite a complex shape and it gets very thick at the root that is made a fiber placement route as well. But there are other alternative ways of doing it as well. So GE use a a 3D weaving machine to make uh a dry part where we're using technology really developed from textiles used for making clothing but much developed but they use carbon fiber textiles and then they make a a 3D woven part and then they infiltrate it with resin. So there's a lot of uh increase in in um automation. Um and it depends on the process. So the aircraft is pretty highly automated. Um some other smaller parts still involve a lot of hand labor and also depends on the economics because in in the west um labor is very expensive. So it's worth investing in these very expensive machines. The fiber placement machines cost several million dollars uh at least each. We have several of them in our uh national composite center. They're very expensive machines, but then they save a lot of work. On the other hand, there's still quite a lot of of manual um interaction because I visited Airbus fiber placement facility and whilst they were laying up this part, they had to stop the machine because one of the tapes was something went wrong with it and they had to remove it and start again.

[01:01:27]There's still some uh actually some manual intervention uh but it's improving and automating it more. So we're involved in research at the university to further automate it. So we we've been working on inspection machines which work on the during the manufacturing spot when the problem arises stop the process reverse it take the tape off and relay it. So automation is is increasing u continually and um let me give you another example from wind turbine blades. Wind turbine blades are currently made largely by laying up all the materials in the mold dry and then infusioning the whole thing with resin. Now that is a very complex and expensive process and if it goes wrong there's a lot of trouble. So one of my uh former PhD students when he graduated he set up a company and uh he has developed a system uh which has been installed for windblade manufacturing where they use cameras all the way along the mold to detect the flow front as it goes up the structure and to run a computer simulation of the infiltration in parallel with the actual manufacturing and then use that to predict if there's a problem if if the resin flows on the edges and and that there could be a dry spot in the middle.

[01:02:49]So if they see that happening, if the AI sees that happening based on the the the flow front, then it will automatically change the valves to to to stop the flow going at the edges and allow more flow in the middle to avoid that dry spot. So previously the company that they installed that had to had scrapped quite a few wind turbine blades and they're very expensive. But since that has been installed then there have been no scrap blades. So that's an example of increasing automation in that case in the wind turbine industry. So uh a few reflections on composites manufacturing.

[01:03:27]It's it's a big challenge and there's a lot of research. It's one of the key areas research at the university to improve the manufacturing and uh to have increased automation but at the same time making sure we maintain quality. In fact automation is is helpful because automation actually does uh um give you a more repeatable product. Hand layout although still widely used can be variable. So uh a few reflections I'm happy to take any further questions on anything that that might have sparked.

[01:03:59]>> Okay. Uh just to recap your answers right uh just to make sure that I actually get it right. Uh so for the first questions your answer is just that for the large part it's just the same way that you would make a a small part like you just make a bowl like >> yes you well usually yeah I mean there are you can make it without people have have been people making parts with with 3D printers now whether 3D printing or additive manufacturing arguably all the con additive manufacturing But but people have been making uh short fiber reinforce using 3D printing machines and not using them all. So they just printed printed on on the on the surface. But the those 3D printing machines do not produce anything like the high strength properties you get with the preer and pre-impregnated materials but but it is an alternative.

[01:04:59]>> Okay. And for the uh your answer for the second question is just a slow and steady progress right so >> I'm sorry the >> for the uh >> second >> for the second questions about the uh the automation >> yes >> for so it's just a slow and steady progress like they're already using like artificial intelligence to spot like resin flows inside the >> yes yeah >> stuff like that right >> yeah so I think there's more work to be done there and exciting researching that's all like questions for today thank you very much for this opportunity >> thank Is there any of you guys that have any questions?

[01:05:48]Uh, let me introduce myself. I'm Ismael Maidento. Actually, professor. I'm a lecturer in in vocational mechanical engineering. I do a lot of uh research about uh composite but actually I will divide it into two question. one if about pressure in when we manufacture the composite.

[01:06:09]Uh I ever do a lot of composite manufacturer usually about info in infusion and the pre-imprognetated uh carbon fiber and then I have a lot of problem with a delimination.

[01:06:24]Uh actually the pressure is uniform I think because I uh vacuum it and when with a vacuum begging and then uh vacuum pump but uh there is a different between this specimen. One specimen is actually get a buckling get a buckling uh failure and then the other get eliminate the the delimination.

[01:06:51]Is it because the pressure is it a pressure affect the manufacturing process? That is my my first question.

[01:06:58]>> Well, so well, let's take that one first. So, so a bit difficult to say without actually seeing exactly what you've got there. Um, one thing I would say is that voidage is very critical. As I'm sure you know, voidage is very critical for competence. If you have voids, then then you can get delamination and premature failure. So, possibly variables in the manufacturing process could affect the amount of voidage which might change the failure mechanism. That's one thought, but I'd be happy to have a a look at that if you'd like. I'm here for a few days and uh we could have a have a discussion about that if you like.

[01:07:35]>> Even a preerre material, we can still get a fight for that for that material.

[01:07:40]>> Absolutely. Yeah.

[01:07:41]>> Preper materials um if they're not carefully laid up, if they're not carefully consolidated, especially if the geometry If you just got a flat plate, then it's it's fairly easy to to lay it up and get the air out. But a particular area of concern is where you have curved structures. You have curved structures and then you put flies on the inside there, you can get bridging across that and that could give rise to to resinrich areas and voidage in the curved region and that's a major source of problems. On the V22 aircraft, they was a carbon fiber structure. They had large frames had a lot of trouble with voidage in the corners and low failures because of voidage.

[01:08:28]And then the second question uh I do uh now I research some adessive bonding between the the different materials between carbon fiber and metals and do some finite element about that and uh do you ever have a doctoral student or whatever do about affinite element you can uh uh give me a tips about that because I do some uh I modeling the adessive bonding with uh has a cohesive zone mode. I think a cohesive zone mode by but uh I can't get the perfect or the uh the correct propagation that uh usually we can see in the practical and experimental experimental experimental procedure. So uh when we when I change the model to the solid and the others I use LSD I think usually LSD usually uh and get the load uh impact load quasatic load but the model is seems uh not works well I think but the cohive zone mode is works but I cannot see the uh what is we called I cannot see the correct propagation as the we see in experimental uh starting but so uh my uh my current research is about a delimination from the other material about uh from carbon fiber and the metal material. Thank you.

[01:10:00]>> Well, another very interesting question.

[01:10:02]I I'd be very pleased to discuss that in detail because we've done a lot of work on uh adhesive bonding and predicting strength of adhesive bonded joints.

[01:10:13]A couple of uh things to mention. things which is really important is I don't know whether you get it with your structures but very often the failure migrates into the composite. So you have an adhesive bonded joint it doesn't fail in the adhesive it goes into the joint.

[01:10:29]So usually what we find is when we're modeling the joints is we use the composite fracture properties not the adhesive. Typically adhesives have much higher fracture toughness than the composites. But if you use those adhesive properties normally it overpredicts the failure because what happens is it finds the weak part which is for the crack to migrate into the composite and propagate in the composite. So that's one very important point. Another point is that adhesive joints are very sensitive to what happens at the fillet at the end of the joint and this is a source of variability and can also affect the predictions and the modeling.

[01:11:17]So, um, that's a a critical question whether you how it fails at the end, but I' I'd really like to see your your joints and your analysis and we could have a discussion about that.

[01:11:42]Is there any of you guys have questions?

[01:11:56]Uh good morning. Uh thank you for the opportunity. First of all, let me introduce myself. My name is Yoga. I am a first year student at its and I have a fascination about the recently viral spa uh space mission from NASA which is the Aremis 2. During its last steps of the mission to get to Earth, the Orion capsule detaches and enters the atu earth atmosphere experiencing temperatures uh almost reaching 2,800 Celsius almost half the temperature of sun's surface. Now uh to my knowledge they used AFC coat for the heat shield which is a advanced composite material made by silica fiber and epoxy for the matrix. And my question is, what would be the difference between the composite they used and carbon fiber composite?

[01:12:50]And would using carbon fiber composite be able to withstand the high temperature that the Orion shields heat shield faces? And as a first year student, what steps should I take if I want to eventually research and develop advanced materials like these?

[01:13:08]>> So, I don't know anything specifically about the art. not worked on that so I don't know the details but we have worked on other high temperature applications we're working with Rolls-Royce on composites for aero engines so the what I mentioned about the fan blades is at the front of the engine which is cool but obviously inside the engine things get very hot and there they're using ceramic matrix composites which is probably similar to what is on the the spacecraft and those consist of ceramic fibers such as silicon carbide and a ceramic matrix. So ceramics are able to withstand very high temperatures, but they're extremely brittle. But if you have ceramic fibers and then you can infiltrate and produce a ceramic matrix, you have a ceramic, but it actually has a fibrous structure and is less brittle and more able to resist the failure. So that sort of material is being used currently in some aerrow engines and it goes up to quite high temperatures. Um for very high temperatures it's usual to use a carbon fiber carbon matrix. So we saw at Garuda they use they have brake discs which they were maintaining on the undercarriage. Those are made of carbon carbon and is able to withstand very high temperatures. Carbon can go up to extremely high temperature. It will ablate. So actually it it gets when it gets very hot, it will effectively burn off. And that probably that's is what happens on the re-entry vehicles.

[01:14:52]probably they're designed to to withstand the the uh uh heat as as much as possible, but they probably do ablate and will need to be uh replaced in some cases. On the shuttle, they use uh ceramic tiles and then they could replace some of those tiles if they were damaged during re-entry. So, I think those materials are made actually they're made in a quite a similar way.

[01:15:17]So you start off with a with a carbon epoxy or very often it's a phenolic a different resin and then they burn off the treatment at high temperature and burn off the other material. So the the what was a a polymer resin just becomes a char of carbon and then because its volume has reduced it's porous. So we infiltrate it again and you go through multiple steps infiltration um firing and then reinfiltration until you have a solid composite which is carbon. You say you have effectively solid carbon carbon fibers but also carbon matrix. Carbon can withstand over 2,000 degrees. It will it will ablate but it will withstand that those high temperature of time and that's that's probably something like that which is what is used on structures.

[01:16:20]So your second question about how how to tell tell me again what you were asking in the second question.

[01:16:29]>> Uh okay, what steps should I take if I want to eventually research into developing advanced materials like this?

[01:16:40]>> So I guess at this stage study diligently I think it's always a good thing for students to do. Um maybe you have opportunity I don't know how your course is structured here but maybe you have opportunities to do a project. So our undergraduates they would do a research project and those that interested that's an opportunity for them to do a project on composites or something that they're interested in. Um so I hope you may have opportunity to do something like that and then if you want to take it further there postgraduate study there's research projects uh you can go and work with a a company working in this area and learn from that. Um some of our students also get involved in activities making structures. I was talking to one of my student the other day and uh in his spare time he's made a a carbon fiber yurt know structure which you put in the garden or outside. He made one of these in his garage in out of carbon fiber. So that was a way of getting some practical hands-on experience. Some of our students also participate in um in projects I was about your UAV uh drone projects here. So there may be opportunities to get involved with with making drones and uh I don't know whether you participate in the the formal student events where where some I visited they have teams making these vehicles from from composite and then they go and race them. So there's many opportunities and uh I encourage you to develop this.

[01:18:25]Thank you so much.

[01:18:36]Do any of you guys have another questions?

[01:18:53]I would like to uh add uh something also with manufacturing of composite material as I did in my PhD study. I did lots of layups in the lab long hours and yeah this was a manual layup so with using a prep and what I what I uh discover is that you could not have a 100% perfect alignment of carbon fiber with using manual layup and this manual layup has still been used in uh industry so uh when you have to using this manual layup hand layup and you would like to make sure that the quality is uh suitable to be used as a structural part. So how you define a good composite structure when you're doing endlight app? Maybe you can uh enlight the audience student and help really to make sure that the quality is is suitable enough as a structural part when you're doing hand layout, manual layout.

[01:20:03]So there are challenges with getting good alignment as you as you say, but that's something you you've just got to be be careful with and you've got to make sure you have things well uh well measured and well marked out.

[01:20:16]There are systems which uh which help with the alignment of the plies laser projection systems which help you to probably you don't have them here but in industry they have these systems which guide the the user where exactly where to put the to get the right alignment. I think in terms of practical steps it's crucial I think it's obvious but it's crucial to avoid contamination. You got to be very careful to avoid anything which might contaminate the layout. So cleanliness is really important. So we do our layout in a clean room. Uh and one of the things we found in the early days is that the vacuum pumps which we were using uh actually produced oil because there was oil in the pumps and that oil actually risk contaminating the layer as it gets in the the vacuum pumps and it can contaminate. So contamination key issue. You got to keep things clean and avoid contamination.

[01:21:20]So that's one point. Another point is making sure you go back to talking about voidage. You want to make sure you avoid having air and trapped air. So when you lay up something, especially if it's thick, you need to consolidate after every few pies to put a vacuum on, remove the air, make sure that as you lay up, you don't have entrapped voids because that can be a big problem. So those are a couple of steps.

[01:21:50]Okay, thank you Michael. And if you have any more question, you're more than welcome. Or are there any question that are being written by the participants in in the list?

[01:22:12]>> Um so Mr. Um with the global carbon market um targets become increasingly strict by this 2026 how is the composite industry addressing the issue of end of life waste given the nature of CFC that are to which I know that are difficult to decompose naturally >> end of life waste and and what was the other one >> end of life waste given the nature of CFCs.

[01:22:41]>> Yeah. So end of life waste is is quite an issue. There's a lot of work going on recycling.

[01:22:49]So we've involved in a few projects in Bristol.

[01:22:54]So one thing you can do, we have a colleague who takes old structure um chops it up and then uses it as a filler for concrete.

[01:23:08]So it actually improves the properties of the concrete and it it's a good way of using the the old material. So that's one thing which we're involved with. So at the National Composite Center they had a project where they had several projects on this. One of which was they took a carbon fiber gas bottle which is a filament wound gas bottle and they unwound it. So they went through a process uh based on steam to to get rid of the resin. And then they actually unwound the the carbon fiber. And then they they made a new bottle, a new structure. I'm not sure it was a bottle.

[01:23:48]They made another new structure using that rewinding that tape that they' taken off an old bottle. So that that's quite an interesting way of doing it.

[01:23:58]And another project they had, they took a Airbus component which was end of life and that was chopped up and again that was processed through this steam process get the fibers and then they you made discontinuous materials out of that lower grade lower quality. You recycle you can't get the the full properties but you can get some quite useful properties to use in a different application.

[01:24:27]was quite successful. We have a a spin out from the University of Bristol from a project which uh which I was involved with where we developed a process for highly aligned short fibers and this this has now been commercialized and what you can do then is you can take chop fiber from recycled fiber either from recycled waste or from end of life parts. Chop it to very small fibers, realign it and produce a recycled carbon fiber pre. So this company Lineat is selling recycled carbon fiber as a new product pre and the properties are quite good. Not quite as as high as as new carbon fiber, but still sufficiently good to be used in many applications.

[01:25:21]They've got a lot of interest from people in using those recycled products because It's very people recognize the importance recycling and so they have interest for example from tennis racket manufacturers a lot of from sports goods actually to to make the products from recycled carbon fiber. So those are a few things I can mention.

[01:25:48]So before committee ask another question. Do any of you guys um have questions regarding seminars.

[01:26:03]One quick question about the sustainably sourced fiber like bamboo that you mentioned. What's the potential that you see this technology being developed in Indonesia? And in terms of reliability, what are your comments on this? Thank you.

[01:26:20]>> So, I think natural materials are are pretty good. They are perhaps more variable than than uh artificial composites, but I think there's a lot of opportunity and a lot of work going on probably already in Indonesia and elsewhere. I've seen quite a lot of work on on using different natural fiber composites.

[01:26:43]They're used aircraft interiors. For example, some of the the cabin the the overhead lockers and plant um panels inside the aircraft are have been made from from flax fibers. Um so I think there there are a lot of opportunities to use these materials because some of them have pretty good structural properties and and they're they're natural materials. They do clearly have issues in terms of variability dealing with moisture. they tend to pick up a lot of moisture uh and so there are some challenges but uh there's a lot of work going on at the moment and I think scope for doing more work and finding the right applications I don't foresee we'll see them for primary aircraft structures because they you really need the the highest performance but for many structures which are are not quite so demanding they make very good materials um so we have a project at the moment one of my colleagues Ben Woods is making trust structures and he started off making carbon fiber trust structures but he's got a PhD student at the moment who makes trust structures using bamboo for the the main longitudinal members and then bamboo is wound with a flax epoxy actually I'm not sure it's epoxy it's biiobased resin um fully sustainable uh project to create these trusses which can take quite high loads that's another I think it's a a good area a good one for for you to be working on here. So I hope we'll have some further discussion about that while I'm here.

[01:28:20]>> Uh thank you Michael. So uh further adding from uh Dr. Fran. So we are part of the UAV research group in uh EAS and we develop a drone in UAV and uh the the name of the research group or the team is Bayutaraka and anyone of you maybe the first year student who would like to join Bayutaraka you're more than welcome and we are developing exciting drone in uh yeah UAF uh where we uh participate in competition and hopefully in the near future we also can use it for more advanced uh technology where we can do a detection of rural area and risk based zone and also also maybe uh detecting damage in aircraft and pipelines uh some kind of that and yeah uh may we by maybe we can take professor Michael later or next week to see our uh workshop where we develop this UF and drone and then we And yeah, you you can have a look and okay maybe uh anyone of you would like to have uh to ask or discussion. Yeah, professor Michael will be here until uh next week.

[01:29:37]So you and he he will be based in the mechanical engineering the second floor.

[01:29:42]So you are more than welcome to have a discussion with him about your research or paper and so on.

[01:30:00]So, any of you guys have questions?

[01:30:02]Since the clock's already nearly at 10:00, this will be the last questions to ask. Please raise your hands.

[01:30:16]Any of you?

[01:30:19]So yeah, some of the students have Okay, first uh thank you for the opportunity for the question. Uh my name is Peter from uh materials engineering and I'm interested in the specific modifications of the fiber. Specifically about the fiber shape. I believe there was a triangle, there was a flower shape. I was wondering if there is a specific reason why you tested those specific shapes. Is it perhaps because how the load is struck load is distributed or it's bonding with the matrix or perhaps uh some other factors regarding the fiber shape.

[01:31:13]>> So there's several points here. So I showed the hollow fibers. So hollow fibers are really very interesting because they're have lower if you if you have if they're empty in the middle of the fiber then you have a a lower density. And from a buckling point of view where you've got compressor failure and buckling you actually get a better performance if you have lower weight and uh so so a hollow fiber provides better performance in compression and buckling.

[01:31:45]In fact, Some work was done on holocarbon fibers as well which do look to have some advantages. So that was the hollow and then in addition to that you can put something inside the hollow fibers to to produce dye or self-healing. With regard to the shapes there's several things. One thing is whether you can get better packing. So if you want to get a high volume the strength and stiffness of a composite depends on the the proportion of fibers.

[01:32:12]circular fibers are not ideal to get the highest packing densities, but if you have these um these triangular type fibers, potentially you can get a higher volume fraction. So that was one of the motivations.

[01:32:26]But what we found in practice was we found that actually those star- shaped fibers I showed had better transverse properties because there was some tendency for the stars to to sort of interlock or to provide better keying in the transverse direction. So we got an improvement in the transverse strength and toughness with those shaped fibers in the fiber direct. We we didn't test the fiber direction. We're just testing the transverse for those fibers. I've seen work on carbon fibers to did did work on different shaped fibers and actually carbon fibers are not always circular. Many carbon fibers have a sort of kidney bean shape. So they're they're not fully circular and there the issue is more about production of the fibers.

[01:33:15]You want to keep a small distance so that any uh volatiles which are produced during the carbonization process can escape and not produce voids or defects in the fibers. So that also issues to do with does the shape of a carbon fiber actually help its manufacturing.

[01:33:35]Most fibers these days are either circular or these kidney bean shapes.

[01:33:41]And um that's a few few points about different fiber shapes. What do you think? Are you interested in different shaped fibers?

[01:33:52]You have any ideas about that that you'd like to explore?

[01:33:58]>> Well, perhaps not now, but it is an interesting concept. I mean, I mean, it is kind of like it's interesting because at a glance, it's not that we can't exactly know the directly like like for example the triangle shape is uh have more packing density but turns out the interlocking of the star shape is more effective at giving the strength and the mechanical properties.

[01:34:31]>> Yeah, >> there's hidden mechanics like that is interesting personally.

[01:34:36]>> Yeah, it's it's it's quite complex and you can do modeling of these things. We do quite a bit of micromechanical modeling where we model the the fibers and the matrix and see what effect it has on the properties. So, uh it's it's very interesting and very complex and plenty of scope for for further research to really understand these things and come up with the optimum design.

[01:34:58]Always a trade-off. You improve one thing then sometimes you find that has a negative effect on something else. So, it's always a a balance between the different properties and trying to get the best combination of properties. the application.

[01:35:13]>> Uh can I add something also and ask the audience who I think who's who's among the audience here that maybe you have designed and then you produce a material and then you test it and uh it didn't go as as you expected.

[01:35:29]Maybe you you did made a specimen and you you you choose your material but and when you test it for example in tension it didn't go as you expected.

[01:35:43]>> Yeah. No.

[01:35:44]>> Am I the only one?

[01:35:48]>> Oh, you're maybe from the postgraduate student. Yeah.

[01:35:53]>> I know that some of you have tested a matter that hasn't gone as you expected.

[01:35:59]Testing material itself is a really really big challenge.

[01:36:04]Testing composites is extreme. Could have heard a whole lecture about that.

[01:36:07]It's it's very challenging. It's much more difficult than people perhaps appreciate any or any more question and yeah you are more welcome to yeah to see Michael during his day here to have a discussion. So yeah and I would like to close with a sum uh to summarize uh this section today. So yeah with composite material is not only carbon fiber but also glass and also natural fiber we have the flexibility to design this uh material as uh any kind of uh load structure application or semiructural application.

[01:36:47]But we really need to understand the behavior of the material and as we can design and manufacture it properly so we can use it use it also properly and yeah I think the key terms is to understanding the behavior of the material in different level. Michael either uh micro level, mero level or the micro uh mechanical level and that needs uh understanding of uh also the modeling and also what kind of appropriate uh suitable testing method that we need to use. So uh uh for that to say we please give a big applause to professor Michael for his really insightful lecture for today. So thank you very much. Thank you.

[01:37:36]>> All right. Um as the clock shows um 10:00 so the Q&A sessions will come to an end. Um thank you very much Mr. Wisdom and Mr. Pu for the amazing discussion and as well to all the participants who have engaged so actively. So um we have now reached the end the today's session and we all and I'm going to invite all the attendees to take photos together. So please Mr. Rishno and Mr. Pu will come to here and stand. So my friends here will help um you guys to organize the positions.

[01:40:20]Consume cigarettes.