Cool Composite Stuff

[Neil1993]

While working on an undergraduate project at my university, I got the opportunity to make a rocket fuselage with an interesting carbon fiber composite. Unlike most carbon fiber composites which use thermosets like epoxy as matrix (the stuff that isn't the fibers) this one used PEEK thermoplastic. I very quickly fell in love with the stuff. It manages to be as light as most professional carbon fiber composites with a density of around 1.44 g/cc but it is also might be surprisingly strong. It was supposed to withstand 4000 N in compression but simulations indicated that it could go up to almost ten times that number. Overall, it manages to be superior to aluminum in most ways (again, this is according to simulation). To achieve this, we stacked sixteen layers of the material in four different directions. This can be seen below:

Another great thing about it is that it rolls off the machine ready to go, only needing for the rough ends to be cut. The manufacturing process can sometimes take less than half a day. You can see the robot that is used to make it as well as a finished section below:

It also has very good dimensional accuracy (mostly due to the fact that it was done by a robot). This means that couplers are a piece of cake. We made one for the rocket's payload bay and its fit was pretty much perfect:

Are there any downsides to this material? Of course! The fact that it is made with a thermoplastic means that it is weaker than other composites at higher temperatures (it melts at around 343 C which is still higher than most thermoplastics).

The biggest problem, however, was the cost. For us, it was about 950 CAD per meter, which puts it out of the range of most people. This is, of course, assuming that you can get access to one of the robots that does this. It is possible that the technology will become more accessible in the future, at which point I hope that its use will become more widespread in rocketry or space applications.

Overall, working with this material was a worthwhile experience and I hope that I've imparted some of my love and interest for composite materials science to the reader.

[mardlamock]

Thats some expensive stuff you ve got there

[Streetwind]

Carbon composites are all the rage among rocket startups right now. Masten Space Systems, Firefly Space, Rocket Lab USA... they're all going for carbon composite tank structures because it's lighter and stronger than metal.

There are quite a few challenges to overcome - for example, most carbon composites do really badly at low temperatures, and well, I probably don't have to tell you about what tends to happen when you try to store large amounts of pure oxygen in a container made chiefly from carbon. But these three companies will have us believe that they've just about solved it, so maybe in a year or two we might be seeing actual test vehicles rolled out onto a pad... will be fun to see how much of an improvement they can manage over a comparable metal structure.

[Neil1993]

In terms of structure, the material we used managed to improve the rocket tremendously. We used a tube that was 2 mm thick, but we would still have been in the green had we halved that value. I'm not to sure about the high/low temperature properties of the material, but it didn't particularly matter in this project, as the fuselage wouldn't be encountering any serious temperature extremes. However, my colleagues working in propulsion have been looking into building composites nozzles, though I'm not really sure about what progress they've made.

[z26]

I guess manufacturing this stuff is difficult since the individual components, while expensive, are nowhere this costly when bought separately. I wonder how better it is than vanilla carbon fiber. Oh, and does making that rocket is simply an excuse to test the material or it has other purposes?

[Neil1993]

I guess manufacturing this stuff is difficult since the individual components, while expensive, are nowhere this costly when bought separately. I wonder how better it is than vanilla carbon fiber. Oh, and does making that rocket is simply an excuse to test the material or it has other purposes?

manufacturing is actually extremely simple. The robot does it all. It's the material that ends up being so costly, as well as the tools (that machine is the only one of its kind in Canada ).

It is always better than CF which is made by hand techniques. It is more uniform and has better dimensional accuracy, which results in it being stronger and easier to design for. As well, PEEK is stronger than most other epoxies that are used. Beyond that, the properties of the part produced depend on the fiber angles that you chose to work with.

The material was actually made specifically for the rocket (the rocket came first). We found that the university had those facilities so we decided to go big on it. I got to learn a lot.

[TythosEternal]

That's pretty cool stuff, and it sounds like a great experience!

Polyether ether ketone has some great properties, and it's got a number of excellent applications. Unfortunately, the aerospace utility is limited as a result of the outgassing and self-dissolution behaviors at low pressures and high temperature, respectively. It's a very common problem for nearly all composite binders, and one the companies mentioned are going to have to solve if they want to do anything more than a single-use suborbital launch per vehicle.

[Neil1993]

Polyether ether ketone has some great properties, and it's got a number of excellent applications. Unfortunately, the aerospace utility is limited as a result of the outgassing and self-dissolution behaviors at low pressures and high temperature, respectively.

yeah, it isn't so good for that...

We had to make sure that the aerodynamic heating and the pressure change wouldn't be serious enough to cause any damage.

This was the first prototype:

[TythosEternal]

yeah, it isn't so good for that...

We had to make sure that the aerodynamic heating and the pressure change wouldn't be serious enough to cause any damage.

This was the first prototype:

That's beautiful! Have any launch recordings and/or performance specifications and/or telemetry data?

[Neil1993]

That's beautiful! Have any launch recordings and/or performance specifications and/or telemetry data?

Unfortunately, it wasn't ready for the first launch time, so we're improving it for the next launch event which is a little less than a year away.

In simulation, it has a maximum velocity of Mach 0.83 and it should travel to around 3160 m. It was built to carry a 10 lbs payload.