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  • Writer's pictureNed Patton

Composites and EVs – A Good News Story

The weight of any vehicle, car or truck, is the primary driver of the vehicle’s range.  Whether that is fuel economy or battery life, weight is the most important thing to a vehicle designer to enable greater range and to set their vehicle ahead of the competition.  And composites is playing an outsize role in the reduction of the weight of electric vehicles in particular. 

The two most prevalent types of composite used in EVs are carbon fiber composites (see the wheel in the lead pic) and glass fiber composites – our old friend fiberglass.  Both of these materials make their way into nearly every part of the evolving designs of EVs, primarily because of their weight savings, but also because they make good electrical insulation, can be made to be very light weight and very stiff, and in the case of carbon fiber, conduct electricity quite well along the length of the fiber. 

It turns out that composites, and particularly carbon composites have found their way into quite a bit of current and upcoming EVs.  This is true from the batteries all the way up to all carbon fiber monocoque body/frame concepts.  So, let’s start at the bottom and work our way up the vehicles to see where composites are being applied.  And that means batteries and battery boxes. 

Carbon fiber composites, primarily thermoplastic composites like sheet molding compound are the materials of choice for EV batteries.  This is because not only are carbon fiber composites light weight, stiff, and strong, they are good insulators because the ends of the fibers are all buried in plastic where they can’t come into contact with any of the battery components.  In addition, the thermoplastics that are used are nearly impervious to the harsh chemistry of the batteries. 

But wait – what about the batteries themselves.  Yes, carbon composites are used as structural materials for both anodes and cathodes.  One implementation of this is a silicon/carbon composite that starts with an industrial battery grade silicon called Silgrain® from Elkem .  This stuff is finely milled and mixed with carbon in powdered form with a binding agent made from carboxymethyl cellulose to stick it together.  The reason that silicon is used is that it is a metallic semiconductor and can hold a charge very effectively.  In addition, both the carbon atoms and the silicon atoms are larger than the lithium atoms so lithium ions can penetrate fairly freely and leave an electrical charge on the silicon.  So, this stuff is a working electrode in a lithium ion battery and has been used in things the size of a coin battery successfully.  So, it won’t be too long before these light weight anodes and cathodes make it into industrial scale batteries which means EV batteries.

Another implementation of carbon fiber composites is in the structural elements for both the anodes and cathodes of what are called Structural batteries (, most of which are lithium ion or lithium iron phosphate.  Researchers in Europe have been experimenting with these structural batteries using several different methods all of which either use carbon fiber composites like carbon epoxy or just carbon fiber tows onto which is impregnated a polymer with either anode active or cathode active materials.  These batteries have the potential to be lighter weight and when they are developed to an industrial scale can also have higher current densities.

Moving on to the large structural parts of the EV, like chassis and frame and most of the body parts, carbon fiber composites in particular are making huge inroads in the EV market.  The stiffness and light weight of these materials make them perfect replacements for all of the steel parts of traditional cars.  Piran composites has an article about this from November 2023 (lead pic in this post is from that article) that discusses the role of carbon fiber composites in many of the structural parts of EVs (  Composites are more damage tolerant and can be better energy absorbers than steel which means that they can enhance the safety of the vehicle while also providing better durability in all types of weather and road conditions.  Composites don’t rust like steel and neither do they fatigue like most metals.  They can take small impact damage without losing their structural integrity as well which makes them more durable. 

There have even been monocoque structures made of carbon fiber composites that include the frame and all of the superstructure of the car.  Lamborghini showed off a monocoque carbon fiber frame for its V12 plug in hybrid supercar last year about this time, right before release of the car itself.  And most of the luxury auto makers are also showing off either monocoque or mostly carbon fiber frame structures for their cars. 

BMW showed off a mixed approach where they married steel parts – especially in the lower part of the frame, and carbon fiber parts in the B-pillars and roof framing around the passenger compartment in their new iX EV.  Carbon fiber has also of course made it into the i3 which is their electric version of the iconic 3-series coupe.  The i3 has an all carbon fiber body and skeleton that not only saves weight but also permits the i3 to pass all of the crash safety tests making it a very safe car for being as light as it is.  And this also increases the range of the EV without having to add more batteries.    

That’s about it for this week.  I hope everyone that reads these posts enjoys them as much as I enjoy writing them.  As usual I will post this first on my website – – as well as on LinkedIn.  And if anyone wants to provide comments to this, I welcome them with open arms.  Comments, criticisms, etc. are all quite welcome.  I really do want to engage in a conversation with all of you about composites because we can learn so much from each other as long as we share our own perspectives. 

I also wanted to remind everyone that I will be speaking at the SAMPE conference in Long Beach in May.  I’m going to be talking about the subject that I have a passion for – composites sustainability.  Maybe I can help the industry a bit again, maybe even rattle a few cages like what happened at the Carbon Fiber Conference in Salt Lake.  One can only hope.  Anyway, for anyone that is interested in materials and process engineering, SAMPE will be a great conference.  And they will have a really great exhibit as well. 

And, finally, I still need to plug my book, so here’s the plug.  The book pretty much covers the watershed in composites, starting with a brief history of composites, then introducing the Periodic Table and why Carbon is such an important and interesting element.  The book was published and made available last August, and is available both on Amazon and from McFarland Books – my publisher.  However, the best place to get one is to go to my website and buy one.  I will send you a signed copy for the same price you would get charged on Amazon, except that I charge $8 shipping.  Anyway, here’s the link to get your signed copy:  And as usual, here’s a picture of the book, for those of you just tuning in. 

If you  live in the Bay Area and would like to meet me, I am doing a book signing at the Stanford bookstore on Friday May 10 at 2 PM.  I’m going to give a brief talk at the start of the signing so if you’re interested and want to meet, even if you have already bought a book, please come by.  I would love to meet you and get to know you. 


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