AC183 From Canada, joined Jul 1999, 1532 posts, RR: 2 Posted (16 years 3 months 3 weeks 5 days 7 hours ago) and read 3072 times:
Well, being an engineering student I had the opportunity to go on a tour of a composite materials plant, as a part of a course I was taking in manufacturing. Now, it's been a few months since I've gone on the tour, and I haven't had gotten around to posting this until now, but I thought maybe some people on this forum would be interested. Anyways, here goes. Also, note that some of the descriptions I'll use are not really technical, I don't know all the technical descriptions and for those I do know, well, I'm trying to communicate an image of the processes involved.
In late November I had the opportunity to visit the Boeing Canada plant here in Winnipeg. Unlike most industries I visited as part of my course, Boeing had a more rigid security arrangement in their plant. In the front lobby, we were greeted by name tags already made up with our names on them, and instructions that our visitor passes strictly had to be returned at the end of the tour. At the entrance there was a display case with models of all the Boeing commercial aircraft from the 707 forward, which looked really nice. Anyways, we were taken upstairs to a training room, where we all gathered and were given a brief introduction by a Boeing communications department employee. Boeing Winnipeg makes mostly composite panels for Boeing commercial aircraft, but also some other types of parts are made or assembled there, also for their commercial aircraft. Anyways, after a little discussion on that we were being split into more manageable groups of around half a dozen students per tour guide, we were taken and shown the plant.
The first step in manufacturing composite panels is to cut the core material. This is what is also known as the honeycomb, because of the hexagonal cells which it is formed out of. The core material arrives at the plant in large blocks of roughly 4 feet by 4 feet by 8 feet (just guessing the size, roughly). The first step is to cut these large blocks into sheets of roughly an inch or two thick. A special saw cuts them into the correct thickness sheets, and various thicknesses are used for different parts. At this point the core material looks like a large sheet of plywood in size, but it has hexagonal holes very closely spaced in that honeycomb pattern so that most of the space is empty in the sheet. If you can imagine stacking many pieces of corrugated cardboard together, and at the wavy end part as the main surface, this is what the sheet of core material looks like, other than the shape of the holes. The real core material is basically a sheet full of hexagon shaped cells. I'm not totally sure what the material the honeycomb is made out of, but just generally it was described as a kind of a plastic-paper hybrid. The sample pieces we were given to look at felt slightly flexible, but quite strong, and had almost a waxy sort of surface texture, if I can describe it as that.
The next thing to occur when making composite panels is for these sheets of core material to be cut into the proper shapes. There are machines used to cut the proper thickness sheets into many various shapes (some machines are computer controlled, some aren't), and the edges of these pieces are sometimes made at an angle, or with a rounded edge, or whatever is required. Rough edges of cut material are cleaned up, and the core pieces are then sent over to be assembled. Now just hold onto the image of what this honeycomb panel is for a moment, because it will be needed in a while, and we'll go to another part of the plant.
The next part of the composite manufacturing process is to cut out the fibre material. This is like a fabric, woven in various patterns out of carbon fibres, or fibreglass. This material comes in a roll, and has to be stored in a freezer until use. This keeps the resins woven into the fabric from breaking down before they are used, but I'll get to that in a moment. Also, there are several different materials used, which have a colour coded plastic film on them to keep track of them. Anyways, this fabric is first thawed out and rolled out onto a large cutting table, to be cut to the correct shape. These tables are probably about 50 feet long, 6 feet wide, and there are several of them in the plant. Then, a computer controlled cutting machine moves down the table, and cuts the fibre fabric into a pattern, and prints an identification number onto the pattern, to identify which part is supposed to be made out of the fabric piece. After the fabric material is cut, it is picked up by workers and placed on trays, or on long trailers, which are taken over to the lay-up area by forklifts. The scrap material is discarded, but the computer process used for cutting the material minimized the waste by using a nesting function to use as much material in the patterns as possible.
Now the lay-up. Various jigs and fixtures in many different shapes are used in this area. What happens is a layer of the fabric material is placed on the shaped jig, and is carefully worked into place with certain tools, and the coloured film is peeled away from the woven fibre fabric. Many layers are put on, some of the parts we saw had over 10 layers of the fabric put on. The jig which is used has markings on it to show where the fabric material has to be placed, and it has to be placed there very smoothly. As you would probably guess, cleanliness is important, and we weren't allowed to touch the lay-up, and all the workers handling the material wore gloves. Then, after all of the fabric layers are in place, a piece of the honeycomb material is placed on the correct spot of the material already on the jig. This honeycomb was previously shaped to fit properly, and after being placed on the lay-up about 10 more layers of fabric material are placed on top of the honeycomb material. This has to be carefully worked into place as well, to make sure the core is competely sealed in between the two sides of the fabric material. Effectively the honeycomb is sandwiched in between the layers of fabric. After this the entire panel lay-up and jig is sealed in a vacuum bag.
The next procedure is to cure the part. Do you remember the resin I referred to being in the fabric? Well, the fabric material has a special polymer embedded inside it. The part is taken in its vacuum bag over to an autoclave area, and the vacuum lines are connected. All of the air is removed from inside the bag so, and the autoclave is shut. What the autoclave does is control the temperature and pressure around the material. It is really just a huge pressurized and heated tube. The combination of pressure and temperature applied to the formed composite part causes the resin to cure. In essence, the resin hardens like a two-part glue, except that it is the pressure and temperature that causes it to solidify, not a chemical reaction between two components. The absence of air inside the vacuum bag prevents any air from interfering with the process. Boeing Winnipeg has a large area full of autoclaves for this process. When the part is removed from the autoclave, which may be up to something like 22 hours later, the vacuum lines are disconnected and the vacuum bag is removed. The panel is not, however, complete yet.
After removal from the autoclave the panel can be taken off its appropriate jig, and the jig is sent back for another part to be laid up on it. The panel is sent for finishing then. The edges of the panels just out of the autoclave are quite sharp, as a single piece of fabric material is quite thin but is now hardened like a knife edge, so it has to be trimmed. A layer of white, light reflective material may be applied to the inside of the panel make it easier for mechanics to see inside of the aircraft with a minimal light source, if the panel is destined for an area where this feature would be useful. Also, the lay-up process is not perfect, so the edges have to be trimmed to the exact final shape and size. After trimming and smoothing the edges of the panel, it is sent for finishing. A light sanding or cleaning may be required before painting, and some hardware may have to be installed on the panel. Such items added to the panel would include brackets to mount it on the aircraft, or other such metal parts needed for the function. Once the panel is completed it is shipped out of the plant to either Seattle or to Wichita for installation.
There are some other notes I wanted to add on to my trip to the Boeing plant. The composite panels I described above are used all over the aircraft. Mostly those were smaller than 6 feet by 4 feet. However, it can be noted that some larger parts are made in the plant. I didn't get a chance to look at the processes used, but a large panel is made for under the belly of the 747, the jig for which is 2 stories high. There are also parts made such as the thrust reverser blocker doors for the 737, the 757, and the 777. There is also a sheet metal area. We observed various components being built such as the structure containing the heat shield, just behind the engine and on the bottom of the engine pylon, for the 737 and 777 aircraft. Needless to say, the 777's assembly was much larger than the 737's. Various other assemblies are built at the plant, I remember looking at a fairly large jig for the production of a part that would have been of specific interest to people on this forum, but I can't remember what that part was.
I think I'll stop there because I can't remember all the specifics of other parts built at this facility, but parts are built for basically all of the Boeing commercial aircraft family at this plant, other than the 717 as I believe it uses a different supply line. I was very impressed by the the plant, and the record keeping of the parts built. In the aerospace industry a log of manufacturing has to be kept for every part, but it is still incredible to see. I found it very fascinating to visit, I learned a lot and I hope you guys all enjoyed learning a little about this, too. I hope I've been clear, if not please just post whatever questions you have and I'll try to answer them, if I can.
Also of interest is some of the other composites facilities in the Winnipeg area. Bristol Aerospace also builds structures for Boeing aircraft, and Air Canada's heavy maintenance base does composite repairs and even has its own autoclave. There is also some research being done by a company just outside of Winnipeg on using an electon beam instead of an autoclave to cure composites. This method allows different things to be done, and cures parts almost instantly instead of a long cure time in an autoclave. It is indeed an interesting time for composite materials use, and it appears they will only be used more in the future, both in the Boeing family of aircraft as well as in almost any other aircraft being developed.
Starship From South Africa, joined Nov 1999, 1098 posts, RR: 13
Reply 1, posted (15 years 8 months 4 days 10 hours ago) and read 2995 times:
You are probably quite surprised to see this topic back on the lead page nearly 8 months after you wrote it, but I felt you deserved a word of thanks for making the effort to write your detailed trip report, which I found very interesting.
It is indeed sad that so few other members of this forum read your post after you clearly must have spent well in excess of an hour putting it together. As I account for at least three of the visits and perhaps you even looked at the final result yourself, it must have been distressing that less than ten people viewed it. Perhaps by resurrecting it again, it will get the readership it deserves.
I was going to e-mail you, but your personal details are sadly lacking in your user-profile. I have added you to my list of respected users.
Ilyushin96M From United States of America, joined Sep 1999, 2609 posts, RR: 11
Reply 2, posted (15 years 8 months 4 days 10 hours ago) and read 2987 times:
Thanks, Nick, for putting that topic back on the top. I read it and found it really informative and interesting! It's strange to imagine that large portions of planes are made from a material that is so light and fragile at the outset, yet through the manufacturing process, becomes so strong.
AC183 From Canada, joined Jul 1999, 1532 posts, RR: 2
Reply 3, posted (15 years 8 months 4 days 5 hours ago) and read 2970 times:
Thank you Starship. I was, indeed, very surprised to see this resurrected.
Initially I prepared this topic after a forum member encouraged me to do so. I intened it to give some insight into aerospace materials. I found (and still do find) that many members hold biases against composite materials, sometimes simply because Airbus has a reputation for using them, and indeed often don't seem to realize that even Boeing makes substantial use of them. In my view these materials, although they are quite expensive, have great potential in many applications. In fact, on another industrial tour I took, we saw the fuel tanks being used at a bus manufacturer which were made of composites, and were being used for natural gas powered buses. While they are not good for all applications, they do offer engineers an appealing option in many uses. While topics like this may have a rather limited audience, I think it was worthwhile posting it if for no other reason than it prepared me to consider what I saw and I was familiar with the processes for my exam. Indeed, as I am now taking another materials science course this term, this could be a timely reintroduction to composites. Thanks.
By the way, if you'd like I can e-mail you, but I don't like to have personal information in my profile for public viewing, as one of my previous ISP's did have some security problems, so I'm perhaps a little paranoid of that...
Starship From South Africa, joined Nov 1999, 1098 posts, RR: 13
Reply 6, posted (15 years 8 months 3 days 10 hours ago) and read 2957 times:
AC183, I think I might have been the person you referred to, that prompted you into writing about the topic. I, in turn, had been reading an in-depth article on the MD-11, another aircraft that made extensive use of composite materials and was interested in hearing more about them.
Please feel free to e-mail me at firstname.lastname@example.org I might be able to forward some info an an interesting all-composite microlite being manufactured here in South Africa. It is a two seater with a fully enclosed cockpit and retractable gear - rather unusual for a microlite. I'll have to search for the info though, as it was a little while since I saw the reports in various local aviation magazines. If I don't find anything on the 'net, I should have a scanner by the end of the week and I can scan the pics for you.
Well, your topic has been viewed a good 50 times more than when it originally disappeared into the archives, so perhaps your efforts were not in vain after all. I think a number of new forum members have been enlightened by your report on the intriguing world of composites.
Various fibre types used in composite material construction could be any of the following: Carbon fibre/Graphite, Aramid/Kevlar®/Twaron®, E-Glass, S-Glass, Polyethylene - Spectra/Dyneema, Boron, Silicon Carbide, or Quartz.
Composite honeycomb material
For some interesting info on composites visit the hotlinked website below, from where the above photos were obtained.
Aca320 From Canada, joined Aug 2009, 0 posts, RR: 0
Reply 7, posted (15 years 8 months 3 days 9 hours ago) and read 2951 times:
Just as an aside I worked at the Boeing plant in Ywg as an nondestructive inspection tech ( when you work in this business it helps to be flexible I have certs in all NDT methods including radiography ultrasonics etc) anyway this was back in 85-87 and at the time one of the most prevalent compisites being used was kevlar this was to change in a very short space of time after an incident which occurred at JAL with one of their new 757's. The a/c in question had sustained some damage to one of the large wing close out panels on the upper wing surface and when the removed the panel they found that instead of weighting 150lbs it weighted 300lbs the panel was cut open and the resin impreg cardboard core was soaked with water.After tests were conducted it was found that kevlar wicks water thereby conducting water to the core although the panels were painted and coated with resin to seal the surface it was found that micro fissures in surface caused by thermo stresses due to operational enviorment (its gets damn cold at 30k ft) as a result we stopped kevlar use and in the space of approx. a month switched to e-glass fiberglass if your interested in more stories just ask I got lots.
AC183 From Canada, joined Jul 1999, 1532 posts, RR: 2
Reply 8, posted (15 years 8 months 3 days 7 hours ago) and read 2950 times:
Chieftain, WestJet just did order 94 firm/option 737NG's. Put into perspective, that's more aircraft than the current combined AC/CP 32X fleet. Also, don't forget that AC/CP have a large 767 fleet, at about 45 aircraft they're the workhorse on many routes, and I've heard that more are on order (probably from CP's long deferred options). And there's rumours that AC is looking to buy a few more Boeings, although Airbus will probably remain on top at AC simply because they suit AC's needs fairly well . Also, there's plenty of other Boeing products operating in Canada, although yes many of them are older, but still, there's actually more Boeing airplanes in Canada than Airbuses, and I think Boeing does stand a chance to gain some more customers in a few years if and when Royal, Transat, CanJet renew their fleets. Also, just to pick on your use of the word "gratitude." Essentially the airlines must buy on the basis of what aircraft best suits their needs. And manufacturing facilities must survive on their own merit, in this case the Boeing Winnipeg operation is kept going by its workforce (skilled workers are hard to find nowadays) as well as by the low cost of electricity in Manitoba to power the autoclaves. The suggestion of buying on patronage is disappearing in todays economy.
Aca320, I have heard that AC is looking to build a new composites facility in Winnipeg. Do you have any info on this, and on when it will be built? Also, any perspectives on the development of electron-beam curing of composite panels? I know a little of what is being done locally at Acsion Industries to develop this, and I believe they're working with Lockheed, AC, and others, and it seems to me that the EB curing technology has great potential to change the way composite parts are made, and to allow new and different parts to be made.
Aca320 From Canada, joined Aug 2009, 0 posts, RR: 0
Reply 10, posted (15 years 8 months 2 days 5 hours ago) and read 2945 times:
AC183 for your info we are building a composite facility and it will utilize an e-beam for curing as well a new autclave. We are doing a fair amount of composite work now and once the split of from air can into our own seperate company occurs there will be subcontract manufacturing here as well. As for the e-beam my understanding of its effects on composites has to do with resin flow and lattice structure of the resin matrix primarily it appears to cause the resin to be more homeogeneous with respect to the chemicals (accerlerates bonders etc) that are found in the resin and results in a better wetting and set-up between the resin and the fibers of the composite also there seems to be less out gassing and fracturing the overall gain in strenght is said to be on the order of 10-15% not to shabby and worth the effort we having been installing trail repaired wing to body panels that used this technique for long term wear and endurance and to validate the repair for both airbus and transport canada approval ,if successful we will be the only repair facility in the world with this approval.