Placeholder Image

字幕列表 影片播放

  • Throughout history, our biggest leaps in technology

  • have occurred as a result of new materials becoming available.

  • I've shown you how it took humankind centuries to master iron and steel,

  • culminating in the explosion of growth during the industrial revolution;

  • how the accidental discovery of age hardening allowed

  • aluminium to take humans into the stratosphere in droves;

  • and how silicon forms the backbone of this age of information.

  • But today, we're going to discover the next great leap in material science:

  • carbon fiber reinforced plastics.

  • Carbon fiber, and its even more futuristic brother, carbon nano tubes,

  • have been touted as the next great innovation

  • that will allow humans to build amazing structures that were once unimaginable.

  • Elon Musk recently revealed an enormous carbon fiber-reinforced plastic cryogenic fuel tank,

  • the largest fuel tank that has ever been created for spaceflight.

  • Building spaceships of this size is not an easy task.

  • The larger the spaceship, the more fuel you need to escape the Earth's gravity.

  • The more fuel you need, the bigger the fuel tank needs to be to hold it,

  • which just adds more mass to the rocket.

  • Carbon fiber reinforced plastics provided a new way to keep the weight down

  • while maintaining the strength needed to withstand the internal pressures.

  • But building a structure like this from carbon fiber is no easy task.

  • This is the sort of material that if it crash-landed on Earth

  • just 70 years ago, it would have been a completely alien object,

  • and we are still learning a lot about its mechanics.

  • The fact SpaceX have created a structure this size out of carbon fiber reinforced plastics

  • that has already been tested at two thirds of its bursting pressure is astounding by itself,

  • but we've yet to see whether it can resist the blistering cold temperatures of the liquid fuels

  • without cracking and leaking, and do it repeatedly.

  • After all, the whole point of SpaceX rockets is to be reusable.

  • Building a cryotank out of composite materials

  • is without a doubt the most difficult part of building a spaceship of this size.

  • Don't believe me? Listen to the man himself say it.

  • Nevertheless, the material will be pivotal in reducing the weight of our craft enough

  • to escape the gravity prison that has kept humans as a single-planet species.

  • Even though we are still learning a lot about the material,

  • carbon fibers by themselves are not as new as you may think.

  • The first carbon fibers were produced by Thomas Edison and Joseph Swan

  • for use as filaments in their new electric incandescent lamps.

  • The carbon fibers they created were produced

  • by carbonizing plant threads like cotton, wood, and bamboo.

  • This material did not have the tensile strength of today's carbon fibers,

  • but they allowed Edison and Swan to replace the expensive Platinum filaments being used earlier.

  • The carbon bamboo filaments Edison developed lasted up to 1200 hours,

  • and they were the norm for 10 years until tungsten filaments replaced them.

  • Not much thought was put into carbon fiber as a structural material

  • until the late 1950's: when the Union Carbide Corporation,

  • a company that manufactured light bulb filaments,

  • began investigating replacements for tungsten filaments.

  • They started using Rayon, an artificial, cellulose-based material.

  • popular as a cheap alternative to silk and cotton as the base ingredient for carbon fibers.

  • This was a breakthrough moment for the start of the modern carbon fiber era

  • as a resulting materials showed potential as a structural material.

  • Researchers all over the world took notice,

  • and just a month later, the Japanese Industrial Research Institute

  • began investigating how to make their own fibers from Polyacrylonitrile or "PAN" for short.

  • The majority of today's carbon fiber is produced with PAN,

  • even though it is an expensive byproduct of oil production.

  • It yields a fiber with a much higher percentage of carbon than Rayon, and it's easier to manufacture.

  • Dr. Shindo created long strands of this PAN material,

  • which he stabilized by first heating it to around 250 degrees for up to two hours.

  • This rearranges the chemical bonding to create a thermally stable ladder bonding.

  • These fibers were then heated again to around 1,000 degrees in the absence of oxygen,

  • which expels the non carbon atoms in the material

  • leaving tightly-bonded carbon atoms arranged mostly in the direction of the fiber.

  • This material was both heat and chemical resistant. It had fantastic tensile strength, and didn't rust.

  • Specialized industries, like aerospace, immediately saw its potential

  • to help spacecraft break the grip of Earth's gravity.

  • And when Gay Brewer won the Taiheiyo Club Masters' Golf Tournament in 1972,

  • using a carbon fiber composite shaft, the material captured the world's attention too.

  • The sporting goods manufacturers all over the world began creating carbon fiber products.

  • Golf clubs, tennis rackets, and racing bikes

  • started to be made with the cheaper off-spec fibers that the aerospace industry could not use.

  • Despite its high price, demand for the material kept growing,

  • and by 1980, 1,000 metric tons were being produced a year.

  • But it was still a notoriously difficult material to work with,

  • and many still doubted its ability as a structural material.

  • During the development of the McLaren MP4/1,

  • one skeptical engineer had said to have picked up a piece of carbon fiber composite

  • just like this and easily snapped it in half,

  • declaring that the material was too weak and brittle

  • to be used for the ambitious carbon fiber composite monocoque.

  • But he was breaking the material across the fibers;

  • if he had attempted to break it along the fibers, he would've had serious difficulty.

  • You see, carbon fiber is made from these tiny thin fibers.

  • This is a picture showing the size difference between a carbon fiber and a human hair.

  • The carbon fiber is the smaller one.

  • These tiny fibers by themselves can't be used as a material,

  • we first have to bind these long strands of fiber together with a plastic resin.

  • Otherwise, they're just a flimsy fabric that can't hold any load other than tension.

  • Here you can see a solid piece of carbon fiber where the fibers are surrounded by white resin,

  • but this technique causes some problems for engineers when designing a product with this material

  • because the plastic is weaker than the fibers.

  • This is a unidirectional layer of Carbon fiber held together with resin.

  • If we pull it this way along the fibers,

  • it has fantastic strength because the fiber is in the same direction as the load, and, thus, can resist it.

  • But if we pull it this way, there is no continuous run of fibers to resist the force.

  • Instead, the resin matrix gets pulled apart, and the fibers add very little strength to the material.

  • To combat this, engineers will layer the fibers on top of each other.

  • Here we have a zero degree layer on top of a 90 degree layer,

  • so, the material properties are the same in those directions.

  • But now, the 45 degree direction is weaker.

  • We can keep adding more layers until we have similar stiffness in all directions.

  • But eventually, the thickness of the material will become too great.

  • We reach another problem:

  • when we remember there is nothing but the resin matrix holding these layers together,

  • and sometimes that fails, and we get de-lamination of the layers.

  • This is why you often see the carbon fibers woven into a fabric like this.

  • But again, woven fabrics can only be so thick.

  • We also need to worry about the drapeability of the material,

  • as these fabrics need to be shaped over molds,

  • and a very thick material like this can make that job very difficult.

  • These issues create a whole lot of work for engineers working with composites.

  • But with experience, we've learned to use these unique material characteristics to our advantage.

  • The designers of the MP4/1 managed to create such a strong monocoque with the material

  • that when the car did crash, it silenced many of its doubters.

  • We can tailor the fiber directions to optimize the material properties.

  • Here, we perform the tensile tests on a tiny piece of carbon fiber composite

  • with fibers only in the direction of the force,

  • creating an incredibly rigid structure that barely deformed through the test

  • and managed to hold 5.3 tonnes before breaking.

  • But stiffness like that is not always desired.

  • For example, in the event of a crash,

  • you want your car to crumble and deform to absorb as much energy as possible.

  • And so composite noses of F1 cars are designed to fragment into millions of tiny bits,

  • and this helps absorb energy and decelerate the car more slowly.

  • Pressure vessels like the Dreamliner fuselage are wrapped in layer after layer of resin-soaked carbon fiber

  • by a robot that places it in the exact right position,

  • making the structure perfect for withstanding internal pressure.

  • One of the big problems when building a structure this big with composite,

  • is that they need to be placed in an autoclave to get the best quality material.

  • An autoclave applies heat and pressure to the material to set the resin

  • and forces the air and other voids that weaken the material out of the resin during the curing process.

  • The autoclave Boeing uses for the Dreamliner is massive,

  • and there isn't an autoclave in the world big enough to fit the tank SpaceX created.

  • It's hard to know how they did it, but they almost certainly used an automated tape-placement robot,

  • like the one in Boeing use to create their own smaller cryotanks,

  • which can cure the resin with a laser as it lays the pre-preg carbon fiber tape down.

  • But it's very hard to create quality parts with this method,

  • as the pressure of the autoclave is essential for removing voids in the resin,

  • And this is such a huge concern for composite manufacturers,

  • that parts are often scanned with ultrasound technology

  • to check that the resin has cured with a tolerable amount of micro-voids.

  • This machine sends ultrasound into the part through a jet of water, and detects the voids in the material.

  • These voids are an even bigger concern for this application

  • because the biggest problem for the material is cryogenic fuel leaking through micro-cracks and voids.

  • Looking at the outside of the tank,

  • I would say with a fair bit of certainty that the tank was made in two halves

  • that could fit in an autoclave, and was then riveted and welded together

  • which I would imagine will be removed for the final version

  • as this just creates weakness in the structure,

  • but this is all guess work.

  • buh-buh-buh-buh-buh buh-breaking news, yeah!

  • So, while I was making this video, pictures were posted to the SpaceX subreddit by u/Death_Cog_Unit

  • showing the remains of the cryotank after being tested.

  • It failed exactly where I said it was going to fail,

  • but SpaceX have yet to make a formal announcement about the results of this new test.

  • This does not mean failure of the project.

  • We test things to learn more, and it's fantastic that SpaceX are pushing the boundaries of what is possible.

  • I still have so many questions about how this thing was made, which just makes it more frustrating

  • that all the questions being asked in the Q&A session after the big reveal were so stupid.

  • This advancement, if we can make it work,

  • will be the most significant leap in rocket technology we've seen in recent memory.

  • Boeing stated that their cryotank provided 40% weight savings over traditional aluminium fuel tanks.

  • That is going to allow us to launch larger vehicles into orbit, reach further into our solar system,

  • and hopefully, not in the too distant future, it will help humans become a multiplanetary species.

  • Thanks for watching!

  • And this episode is once again brought to you by SquareSpace,

  • who helped me make my next move with my website.

  • In my last video, I revealed I was working on building a site

  • that would continue my mission of sharing the amazing engineering

  • that surrounds us in our daily lives.

  • And this week, I can announce that the site is finally live at:

  • www.RealEngineering.net

  • And it's looking great, thanks to SquareSpace.

  • SquareSpace allows you to create a beautiful website or online store with award winning templates.

  • They have 24/7 customer service,

  • and their intuitive design platform makes it easy to create the website you dreamed of.

  • You can make your next move with SquareSpace too,

  • and build a beautiful website by using the code "realengineering" for 10% off your next purchase.

  • Thank you, SquareSpace, for helping Real Engineering exist both here on YouTube

  • and on our beautiful new website.

  • If you'd like to follow our progress as we build this site,

  • please sign up to the newsletter on the site.

  • And thank you to all my viewers and Patreon supporters, too.

  • I'm close to making my first hire for this channel to make more of the content that you love.

  • if you'd like to support Real Engineering, please consider supporting us on Patreon

  • or maybe even buy the new Real Engineering t-shirt,

  • which is available as the $20 reward on Patreon, or over on store.DFTBA.com

  • If you'd like to see more from me,

  • the links for my Patreon, Facebook, Twitter and Instagram accounts are in the description.

Throughout history, our biggest leaps in technology

字幕與單字

影片操作 你可以在這邊進行「影片」的調整,以及「字幕」的顯示

B2 中高級 美國腔

碳纖維(Carbon Fiber - The Material Of The Future?)

  • 1 1
    joey joey 發佈於 2021 年 06 月 09 日
影片單字