As quoted from the Aptera news article: “The majority of the BINC is made of Carbon Fiber Sheet Molding Compound (CF-SMC), combined with Glass Sheet Molding Compound (SMC).” (Note: the BINC is the “body in carbon”).
It also states: “Carbon Fiber-SMC is a lightweight material consisting of a random arrangement of short fibers that make it possible to mold intricately shaped parts. It offers much higher stiffness and strength than standard SMC. Because it can be press-molded, this process substantially reduces manufacturing time for the BINC and allows Aptera to begin delivering vehicles to customers more quickly.”
This randomly oriented short fiber composite was new to me, so I was curious to learn more. Today I’ve found out you can actually buy kits of this type of material and quite easily create your own carbon fiber products. Check out the very easy to follow and highly informational instruction video below:
Next, the same guy who teaches us how to make parts using short fiber carbon composite also tests these parts for us and does a rather excellent job of unveiling its properties and comparing it to aluminum and a few other materials. If you’re into a bit of technology and would like to get a feeling for the mechanical properties of the short fiber carbon composite, be sure to check out this video:
My take: Aptera related
Of course, the material used in the above video’s won’t be the exact same material used in our future vehicles. Slightly different resins and probably a different supplier and fiber geometry will be used. Also, I expect the fiber orientation to be more controlled and therefore better entangled in the CPC products. However, the basic properties are what I would have expected (I am a mechanical engineer myself).
The material features excellent bending strength, stiffness and weight. Pure tensile strength is slightly less than aluminum (it could very well outperform aluminum in the CPC products) and composites with longer strands, but this might not necessarily be an issue. It all depends on how the components are being loaded. And on those locations where tensile loads do become critical, it might be feasible to add in continuous strands of carbon to improve performance locally. Also, note that it is much easier to use variable thickness in each part, to drastically reduce local stresses. This means that even if the material is weaker than conventional carbon fibre composites, the actual part could be stronger, since the stresses are spread out more evenly.
To me, this new material choice for specific parts of the vehicle seems like a very good idea. It’s relatively easy to produce, making it less time consuming and more cost effective. Still, it offers significant benefits over materials like aluminum.
I can’t wait to see the parts in more detail, to discover which technique Aptera chooses to use for which specific part.