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Replacing Aluminum Parts with 3D-Printed Carbon Fiber

Recently, a major shortage of aluminum amongst industry suppliers has led to steep price increases. Since January 2021, the aluminum prices have increased by over 50%, and experts project increases to last through the next two years.

According to Jyske Bank, the worldwide aluminum shortage can be traced back to increased material consumption due to three factors: increased spending on consumer goods due to stimulus packages, increased investments in sustainable technology which rely on use of aluminum (such as wind turbines, electric cars) and Chinese production and consumption of aluminum.

In light of this aluminum shortage, Markforged Carbon Fiber offers a suitable alternative, as many of our customers use it to replace parts made out of machined aluminum. Carbon Fiber has the highest strength-to-weight ratio of our reinforcing fibers. Six times stronger and eighteen times stiffer than Onyx, Carbon Fiber reinforcement is commonly used for parts that replace machined aluminum.

When laid into a Composite Base material like Onyx, it can yield parts as strong as 6061-T6 aluminum. As a material, it is extremely stiff and strong, and can be automatically laid down in a wide variety of geometries by Markforged 3D printers to produce optimized parts.

What is Carbon Fiber?

Carbon fibers are made up of carbon atoms organized into long, crystalline fibers just 5-10 microns in diameter. In modern manufacturing, several thousand carbon fibers are bundled together into tows and combined with other materials to form a composite. When joined with a thermoplastic or thermoset resin matrix, carbon fiber tows can take various forms for use in engineering applications.

Carbon fiber’s specific material properties make it ideal for a wide variety of applications, which include:

  • High stiffness and tensile strength (as strong as aluminum)
  • Far lower relative density than steel and aluminum
  • Resistance to heat and chemicals

What makes Carbon Fiber an ideal replacement for aluminum?

Using Continuous Fiber Reinforcement (CFR), carbon fiber can achieve a similar strength to aluminum, with the ability to replace machined components in application. This is due to its enhanced stiffness, impact resistance, heat resistance, and durability.

CFR allows flexibility in how users can implement continuous fibers in their parts - users can control how much carbon fiber is inserted into parts, as well as where specifically in the parts the carbon fiber tows are placed.

Carbon Fiber properties

Compared with 6061 aluminum, 3D printed carbon fiber has a 50% higher strength-to-weight ratio in flexure, and a 300% higher ratio in a tensile moment. Carbon fiber continuous reinforcement has been used to create conformal jigs/fixtures and specialty tooling for some of the largest and most prestigious global business through to one-off end-use parts for high-end motorsport applications.

Furthermore, reinforced Carbon Fiber has a flexural strength of 540 MPa, compared to 6061-T6 aluminum (<480 MPa).

Click here for a comprehensive rundown of Carbon Fiber strength measurements.

How does Carbon Fiber printing work?

Markforged printers start by forming the outer shell and infill of the part using Onyx, a thermoplastic filled with short-strand chopped carbon fibers. This step of the process is known as fused filament fabrication (FFF).

A secondary nozzle is then used to inlay long-strand Continuous Fiber Reinforcement (CFR), selectively reinforcing the perimeter, select features, or entire layers of the part. Using CFR, parts can be strategically reinforced in different ways to fit different specific loading conditions.


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