Composite 3d printing

3D Printing Carbon Fiber and Other Composites

Composite materials, on the other hand, are parts made up of more than one material that, when combined, have properties different from their original materials. Materials like concrete and particleboard can be considered composites, because they are mixtures of a variety of materials. However, when we talk about composites from an engineering standpoint, we usually refer to composites with reinforcing fibers. Carbon fiber, fiberglass, and Kevlar are three of the most common fiber materials used for composites in industry. As we covered in the Physics of 3D Printing, the fibers are like spaghetti - thin, brittle, and easy to snap if bent. These fibers are almost never used by themselves - they are woven into sheets, wrapped into rods, or formed into custom molded shapes with the help of a matrix material to harden the fibers into an optimized shape. When many fibers are bound together to create larger structural elements, forces can distribute and disperse loads along the lengths of all of the fibers.

Fiberglass strands being laid down in a mold and cured with a thermoset resin.

Carbon fiber has one of the highest strength-to-weight ratios out there, making it very valuable for creating lightweight, strong parts. The fibers themselves are made up of carbon atoms whose crystal structure is aligned into strands, making the strands incredibly strong in tension. Traditionally, thermoset resins are used as the bonding agent to set these fibers into a designated shape, cured around a matrix material like foam. So you can create a sandwich panel by “sandwiching” the foam between to sheets of fiber weave, and curing it all with resin. In the context of 3D printing, the fiber can take two different forms:

Chopped Fibers are short-length fibers chopped into segments less than a millimeter in length and mixed into traditional thermoplastics to form what is called a filled plastic. These can be printed with an FDM printing process.

Continuous Fibers require a slightly different 3D printing method, in which continuous fiber strands are coated in a curing agent and laid down into a thermoplastic matrix extruded via a secondary print nozzle. This process is called Continuous Fiber Fabrication (CFF).

Two forms of 3D printed carbon fiber: on the top is a chopped fiber 3D printing filament, and below is a continuous strand of carbon fiber.

‍

Either way you add fiber, the addition of the fibers boosts part strength and other material properties, but the amount it helps differs depending on the way that fiber is used, and what fiber it is. Generally speaking, a continuous carbon fiber 3D print is stronger than chopped carbon fiber 3D because the continuity distributes any applied loads.

Chopped Fiber 3D Printing Materials

Chopped fiber filled plastics are the most common type of composite 3D printed plastics. The most widely used chopped composite 3D printing material is chopped carbon fiber - where carbon fiber pieces are mixed with traditional 3D printing plastics like nylon, ABS, or PLA. Adding this “filling” to thermoplastics is a material booster pack. The fibers take on some of the stresses of the part, like how concrete is added to cement to boost its strength. The fibers handle some of the applied stresses on the part, boosting the properties of typically lower-grade materials. The addition of carbon fiber also improves the thermal stability of mechanical properties, which widens the range of operating temperatures and improves predictability of material behavior in both high and low temperatures.

A close-up of chopped carbon fibers used in 3D printing, taken on an SEM.

These fibers are chopped up into fine pieces and mixed into the plastic before it gets extruded into a spool for use with material deposition-based 3D printers. In this case, the 3D printing process remains the same, because the fibers are just suspended in the thermoplastic - so it gets heated, extruded, and cooled into the part just like any other FFF style 3D printed. Chopped composite 3D printing materials take normal plastic that may be lacking in certain properties and boost it. In the case of carbon fiber, the fibers boost the strength, stiffness, and dimensional stability of the part to make it higher-performing than its base plastic.

Chopped carbon fiber 3D printing materials can be used like normal 3D printing plastics, boosting some material properties.

The quantity of fibers and the length of chopped segments impacts the strength and quality of the part. Different vendors blend different amounts of fiber into their plastic, yielding materials with different strengths. Below a certain threshold, and the fibers boost surface finish, print quality. Above that threshold, mixing in a large quantity of longer fibers, and you get a stronger material, but you sacrifice surface finish and part accuracy because there is a smaller percentage of plastic in the material overall. The thermoplastic is essential to the mixture because it makes the printing process work well, so your parts can only get so strong.

Continuous Fiber 3D Printing

Continuous fiber 3D printing adds continuous strands of fiber reinforcement to the part (think back to fiber strands), to achieve metal-strength properties at a fraction of the weight. Using two print nozzles, the printer builds the matrix material out of a thermoplastic, and irons down continuous strands of continuous fibers into the part. This process is called Continuous Fiber Fabrication (CFF).

Continuous Kevlar strands are ironed into this part to increase its impact resistance with a composite fiber printing nozzle. A thermoplastic matrix material forms the skin and core of the part.

The power of CFF comes from the continuity of the strands. Unlike chopped fibers, continuous strands can absorb and distribute loads across their entire length. When placed within a thermoplastic matrix, the part can handle higher loads and absorb larger impacts. This allows these parts to achieve the strength of metal at a fraction of the weight.

Continuous fibers form the backbone of a 3D printed part, because the loads distribute along their length, rather than into the plastic.

The CFF 3D printing process consists of two steps per layer - first, a thermoplastic is extruded to form the infill and shells of the part - this serves as the “matrix” material of the composite. Next, the continuous fiber is ironed into that matrix, fusing with the thermoplastic by use of a compatible resin coating. This process repeats layer by layer, forming the fibers into the backbone of the 3D printed part, while the thermoplastic acts as a skin. This process is also similar to how rebar can be laid down inside concrete to reinforce it.

The fibers form the "backbone" of the part and can be laid down in specific patterns to optimize a part’s strength for its weight and material consumption. You can place fiber in specific areas based on how the part will experience load, putting the strength exactly where you need it. This is very different from standard deposition-based 3D printers, including with chopped fibers, because these methods have an even distribution of properties throughout the entire part. Different fiber reinforcement options can be used for different loading conditions and behaviors. You can learn more about the different reinforcement strategies in Fiber Reinforcement Strategies.

A variety of different fibers can be used for reinforcement as well, depending upon what material properties your part needs to have. Markforged 3D printers offer a few different fiber materials so that you can choose the strength behavior of the reinforcement:

Carbon Fiber is a stiff and strong fiber that behaves like 6061 Aluminum, so it can be used for lightweight components that support heavy loads.

This 3D printed carbon fiber can match the strength of aluminum when continuous. Both are supporting a 27.5 lb load.

Fiberglass is a sturdy, cost-effective reinforcing material with some compliance to it. It boosts part strength above that of plastics and is a good starting point for printing with reinforcement.

Fiberglass is a robust 3D printing fiber option, exceeding the strength of chopped fiber, ABS, and PLA when supporting a 7.5 lb weight.

Kevlar has high toughness and shock resistance, making it ideal for shock-loading and high-impact conditions. It bends instead of breaking.

PLA, ABS, and Kevlar reinforced 3D printed parts getting shock-loaded with some big hammer hits!

High Strength High Temperature (HSHT) Fiberglass maintains its strength and stiffness at high temperatures because of its high heat-deflection temperature. Its heat resistance allows it to hold up in more extreme environments.

This test was performed after heating each beam to 300 degrees Fahrenheit in an oven. HSHT does not lose strength at high temperatures, so it still supports the 5 lb load.

So between selecting different fiber types for certain material needs, and controlling where the fiber can be placed layer by layer, you can control the behavior and performance of your parts. This is one of the primary advantages continuous 3D printed composites have over chopped fiber materials. Not only do you get stronger parts, but you also can produce parts optimized for their application.

Composite Materials for 3D Printing: What Should You Know?

Published on July 26, 2021 by Madeleine P.

In recent years, composite 3D printing has become increasingly popular. One of the youngest branches of 3D printing, this technology is now used by many players in additive manufacturing, such as Impossible Objects, a company specializing in the field. In fact, it has become so popular that some studies estimate that the composite 3D printing market will reach $1.73 billion by 2030. Logically, when we talk about composite 3D printing, we think of composite printers, but also of composite materials, which are at the heart of this process. Composite materials are made of at least two components and have special properties, making them uniquely suited to various industries that use 3D printing.

Most of the time, in order to manufacture these materials, it is necessary to mix a plastic, which we will call the matrix, with fibers. Today, there are many different kinds of fibers, but three are mainly used for 3D printing: carbon fiber, which is probably the most popular, fiberglass, and PPD-T, also known as Kevlar. Depending on the requirements, either short or long fibers can be used. Short fibers are integrated into the entire matrix and will reinforce the entire part; this type of material is compatible with a wide variety of 3D printers. Long fibers are placed during the printing process itself and are not cut into small pieces, allowing reinforcement only where it is needed. They are only compatible with certain machines at this point in time.

Printing a composite material (photo credits: SABIC)

Carbon fiber-filled materials

As previously stated, composites made from carbon fiber are the most common in the additive manufacturing market. First produced in 1860 by chemist Joseph Swan, carbon fiber, as the name suggests, is composed of many carbon atoms bonded together. It is considered by many to be the most efficient fiber for creating composite materials. Indeed, materials made from this fiber have high stiffness, high tensile strength and good chemical resistance. In addition, these composite materials are characterized by their low weight and high temperature tolerance – they are especially known for their weight/strength ratio, which is twice as high as that of aluminum, for example.

Carbon fiber composites can be found in many fields, such as aerospace, automotive, civil engineering and many others. Matrix materials such as PLA, PETG, nylon, ABS or polycarbonate become stronger and lighter when it is added, and carbon fiber can also be mixed with ceramics. The creation of these composite materials has led to the development of new applications in the printing industry, such as the first 3D printed electric scooter made of carbon fiber.

3D printed part made from carbon-filled nylon (photo credit: Stratasys)

Fiberglass-filled composite materials

Patented in 1930, fiberglass is, like carbon fiber, used to reinforce many polymers. However, compared to carbon fiber-filled materials, materials made from fiberglass are less rigid but also less brittle. It is mainly for these reasons that fiberglass-filled materials are mostly less expensive. Nevertheless, fiberglass offers good mechanical properties. In addition, it is considered to be a good electrical insulator and has low thermal conductivity. It is more comparable to other polymers: for example, it is 11 times more rigid than ABS.

Whether in the construction, marine or even sports sectors, this composite material is now widespread. For example, in collaboration with Autodesk, Catmarine, Micad and Owens Corning, Moi Composites has created the MAMBO boat, the first 3D printed boat made of fiberglass.

Prototype of a bridge part printed using fiberglass (photo credits: CEAM)

Kevlar-filled materials

As with the other fibers mentioned above, Kevlar is regularly found mixed with several types of plastic to obtain composite materials. Kevlar is a registered trademark of the DuPont de Nemours company, first commercialized in 1971 and invented by Stephanie Kwolek. A member of the aramid fiber family, Kevlar is one of the most wear-resistant materials, known best perhaps for being one of the first materials used for bulletproof vests. With good mechanical properties in traction and fatigue, Kevlar is mainly used to manufacture parts exposed to strong vibrations and needing to resist abrasion. It is five times stronger and lighter than steel, and also has high heat resistance – it can withstand temperatures up to 400°C. Kevlar also has a low density.

As far as additive manufacturing is concerned, Kevlar is mainly used in the automotive industry, although, like all composite materials, it can be used to 3D print any object. Aptera Motors, an American company, has partially 3D printed a car using this composite material. We are also thinking of test parts, which have to resist to important shocks

Kevlar filled ABS filament (photo credits: Markforged)

What do you think of these composite materials? Let us know in a comment below or on our Facebook and Twitter pages. Don’t forget to sign up for our free weekly newsletter, with all the latest news in 3D printing delivered straight to your inbox!

3D printing with thermoplastic polymers: 12 domestic projects

Implementation stories

Rapid prototyping

Experts recommend

Author: Semyon Popadyuk

Thermoplastics and composites - what is it? | How are composites made? | Who are the main consumers of 3D printing resins? | What plastics are the most popular? | How is 3D printing with thermoplastics and composites applied? Examples of finished products

We are often asked the question: do they make high-quality, reliable and safe materials for 3D printing in Russia? Of course, there are such manufacturers, moreover, significant experience and know-how have been accumulated in this area. One of the pioneers in the domestic market for the production of plastics for the additive industry was REC. It is directly involved in the production of filaments, and its 3D Solutions division conducts R&D on the creation of composite materials.

REC and 3D Solutions in facts and figures:

8 years of work with thermoplastics in the field of additive technologies;
22 different types of FFF filament material are mass-produced;
in 2020 and 2021, more than 130 different compositions based on thermoplastics were produced and tested;
own production equipment and laboratory complexes for the production and testing of thermoplastic compositions both in molding and in 3D printing;
the most recognizable brand in the field of FDM printing materials.

Dmitry Miller © youtube.com / JsonTV

Today, in our blog, REC and 3D Solutions Executive Director Dmitry Miller shares his experience in the development and application of thermoplastics and composite materials and talks about the most interesting FDM technology implementation projects.

Check if a 3D printer will solve your problems - order a free test 3D printing service from iQB Technologies!

Thermoplastics and composites - what is it?

A thermoplastic is a polymer that can become plastic when subjected to temperature. Based on thermoplastics, composites are produced - pure plastics in combination with other materials, for example, ABS with polycarbonate or reinforced with carbon fiber. There can be a huge number of such variations.

For eight years on the market, we have managed to work with most of the existing plastics, including ABS, ASA, SBS, SEBS, PA, PP, PSU, PPSU, PEEK, PC, TPU, TPEE, PET, PETG, PEI, PLA, PS, PTFE, PVA, PMMA, PBT. And this is not a complete list - some materials, such as PVC, could not be brought to an adequately usable state, because there are all sorts of difficulties with processing.

How are composites made?

We take the necessary polymer base and, depending on the task and the required properties of the material, we modify it with certain components. These include:

A wide range of fillers with different properties is also used. These are the most familiar carbon fibers, and fiberglass, and basalt fiber, and Kevlar fibers. To obtain certain properties, it is possible to fill the polymer with hollow glass spheres and carbon nanotubes.

We also have metal-filled polymers used in MIM (Metal Injection Molding) molding technology. It is more correct to call them metal-polymer compositions, since they contain more than 93% metal and at least 7% binder. A product is molded from such a composite material using casting or 3D printing, then the binder is chemically etched, the resulting model is baked in an oven, and finally we get an all-metal part.

In addition, compositions exhibiting ferromagnetic properties can be obtained. They are in demand in tasks related to radiography and radio electronics.

iQB Technologies experts recommend the article: Additive Manufacturing of Molding Tooling from Polymer and Composite Materials

Who are the main consumers of 3D printing resins?

Our main consumer is production, since additive methods create either the final product, or some part of it, or tooling for its production. A large number of orders is due to the regularity, systematic repetition and stability of the production process.

Slightly more than a quarter of the volume of production is engineering companies that are engaged in 3D printing of prototypes for assembly testing, visual models and the like.

A large layer, accounting for 25%, is the sphere of education. Thanks to federal programs such as "Point of Growth", 3D printers are supplied to many educational institutions, and additive technologies are an educational subject. Teaching the basics of 3D printing makes a huge difference as it helps students change the way they think. When we use classical subtractive technologies - turning a blank or cutting it with a laser, cutting something out of a flat sheet - this is one way of thinking. Additive manufacturing removes many restrictions, thinking is completely different, and the next generation will think in technical terms much more freely.

The next segment is occupied by personal consumption, which can affect absolutely any area. These are people, as well as small businesses, using 3D printers for their own purposes, hobbies.

And finally, medicine. So far, the amount of work we have in this area is small, but there are precedents for application. Polymers are used for the additive production of orthoses (devices for fixing limbs), prosthetics, and, together with educational institutions, for the manufacture of anatomical models for various medical needs.

What plastics are the most popular?

For clients of REC and 3D Solutions, PLA occupies the first place in terms of consumption. This is well deserved, as it is easier to print than any other plastic, and it is the least demanding on equipment. Any simplest personal 3D printer will work fine with this material, and there will be no difficulties.

The second place is approximately equally divided by ABS and PETG materials. They are used in functional prototyping, where PLA is far from always applicable due to its extremely low heat resistance: at 50 degrees it is already soft.

Next come various composite materials, and this segment is growing from year to year. In the next five years, they are likely to come out on top due to the ability to achieve any desired properties.

And a very small segment (4%) is made up of polyurethanes, ester elastomers - any flexible and elastic polymers. They are used by customers of all other materials, but for certain tasks that require elasticity and flexibility.

How is 3D printing with thermoplastics and composites applied? Examples of finished products

1. The prototype of an unmanned taxi and its components printed using FDM technology

Before you (Fig. 1) is a functional prototype of an unmanned taxi, containing a huge number of details. To make each of them by classical factory methods is quite difficult, expensive and time consuming. Thanks to 3D printing, the manufacturing company has optimized the process of creating many parts - reflectors for front optics, brackets, holders, decorative elements, etc. Models drawn on a computer were immediately printed and installed on the spot - so, as quickly and simply as possible, project of a fully functional working prototype vehicle.

2. Grip for the robotic arm

An interesting example is when materials are combined for 3D printing. In the photo above, you can see the grip for the arm of the robotic arm. The claws themselves are printed from hard PETG plastic, while the inner pads are made from elastic material. It ensures that objects will not slip out of the manipulator's hand.

3. Model of the fuel system of the Angara rocket. Printed from ABS plastic, used to test the assembly of a complex device

Let's move on to complex systems. Figure 3 shows a real layout of the Angara space rocket power supply system, printed from ABS plastic, on which the assembly was checked. It was necessary to test whether the developed device with a large number of components can be assembled without damage.

4. Elements of LED lamps (medium runs)

And here you see how it is possible to produce complete end products using 3D printing. The company is engaged in the manufacture of LED lamps in small series. Some models have plastic elements - plugs, light diffusers. All products are designer, original, it turns out to be more expensive to make a thousand pieces by casting into silicone, not to mention the classic casting of molds: in such a run, the mold will not pay off at all, the parts will turn out to be “golden”. In this case, 3D printing is an extremely profitable solution. Unlike casting in silicone, additive manufacturing allows more freedom in geometry and a batch can be produced very cheaply and quickly.

The production speed is determined by the capacity of the 3D printer farm. As a rule, when we integrate 3D printing into production, we do not limit ourselves to one machine and create a farm. This is a whole fleet of identical additive installations to which the job is sent, and they immediately start printing together. In this way, we can significantly increase productivity. It is easily scalable and quite cheap, especially if FDM is used - the most affordable of all 3D printing technologies.

5. Pots for levitating plants (small runs)

A curious startup project that specializes in levitating plants (Fig. 5). A tree in a pot flies over a wooden block, a magnet device works. So, the task was to make a planter. It should be light, not clay, so that it is easier to make a magnet, and not be afraid of such environment as earth, fertilizers and water. At first, there were attempts to produce wooden pots, but the wood, even with protective coatings, eventually deteriorated from the internal environment. Therefore, it was decided to introduce 3D printing with plastics. The company ordered 3D printing from us, but when it became clear that the production was profitable, it purchased equipment and materials and began to produce pots of various designs on its own.

6. Model of the foot, made according to CT

Medicine cannot be overlooked. The photo shows a model of the foot printed from white plastic based on the results of computed tomography. The 3D model was obtained from CT and sent to the 3D printer. The product has two uses:

students with the help of such realistic models can practice, identify pathologies, since the use of real bones is very limited;
using this model, it is much easier for surgeons to plan an operation strategy and make it more accurate on the patient.

7. Prototype of endoprosthesis

Another medical device is a prototype endoprosthesis (Fig. 7). This is a preliminary model made of plastic, which is used to check the accuracy and correctness of the prosthesis. The final product is also created on a 3D printer, but already from metal, using SLM technology, obtaining a high-precision model of an individual endoprosthesis on the first attempt. Medical metal has a high cost and, in order to eliminate errors, prostheses are initially printed from plastic.

Read on: Plastic works wonders: how a 3D printer imitates human organs

8. Figures in the Olympic Museum in Sochi, printed on a 3D printer

Now let's see what benefits you can get using large format resin 3D printing. One of the most common areas of application today is the production of small architectural forms: sculptures, statues, decorative elements, architectural decorations (Fig. 8). Using a 3D printer, such models are created easily and quickly, and this is one of the cheapest ways to manufacture. In addition, there is the possibility of a wide choice of materials, adding optical effects, translucency (for example, to build a luminous element inside the sculpture for a greater effect).

9. An example of the texture of a printed product of large dimensions

As you know, FDM printing has one feature: due to the layered construction, the parts are “striped”. However, this disadvantage can be turned into an advantage and interesting textures can be created using a large-format 3D printer, as in Fig. 9. Of course, first of all, this is the production of designer furniture and various decorative elements and architectural forms.

10. 3D printing with foam composite

For 3D printing of large objects using FGF technology using polymer granules, there is a separate layer of composite materials. On fig. 10 shows the process of printing with a material resembling polyurethane foam. The similarity is not accidental - a foaming composite is used here. One cubic meter of raw material yields 25 cubic meters of foamed material. And, as you can see, this technology allows you to achieve very large layer heights, and the thicker the layer, the faster the 3D printing. And a slight decrease in density facilitates the entire structure as a whole.

Learn more about large-format 3D plastic printing: solutions, challenges, case studies

FDM/FGF printing has a very low accuracy. Moreover, materials have different shrinkage, and in the case of different geometry of parts, shrinkage will be non-linear, unequal simply because of the peculiarities of the technology itself - because of how the material is laid, what temperature loads are applied. In the case of tooling production, as a rule, hybrid technologies are used - the model is printed, and then the working surface is milled. In this way, we obtain the desired roughness and precision.

Different equipment requires different materials. Somewhere high heat resistance is needed, somewhere high strength, and somewhere the lowest possible price is a priority. There is an optimal material for each task.

And there is a huge field for optimizing production in order to produce large enough objects cheaply and in an incredibly short time - literally in a matter of hours.

Article published on 11/12/2021, updated on 09/20/2022

Composite printer: breakthrough 3D printing technology created in Russia | Articles

Russian developers have proposed a unique 3D printing technology that allows you to create composite parts of any shape. During their production, the strength losses characteristic of traditional manufacturing methods will be minimized. Until the end of 2018, prototypes of new devices will begin to be used by companies such as BMW and Airbus, and their introduction into mass production is expected in a couple of years.

Despite the outstanding characteristics of composite materials, many industrial companies are in no hurry to implement them. Modern carbon plastics may lose some of their properties in the process of creating final products from them. This is due to one of the main features of composites, which is that they are able to resist loads in only one direction - along the laying of carbon fibers (they have anisotropy), which forces manufacturers to put up with the loss of strength of final products for the sake of universality of their mechanical characteristics. However, Russian developers figured out how to turn the inconvenient feature of the material to good use.

The new Russian 3D printer , created by the developers of the Anisoprint company, is able to control the trajectory of carbon fiber laying at each point of the product. Thanks to this, specialists are able to add strength where it is critical.

In addition, the new equipment should save manufacturers of composites the need to drill holes in composites for subsequent assembly of parts. It also significantly reduces strength and can lead to significant complications (in particular, the appearance of such a problem with the fuselage parts of the Boeing 787 Dreamliner slowed its time to market by several years).

- Instead of laying layers of fibers in different directions and then drilling a hole in this array that will destroy its structure, with our printer we can run reinforcing threads around the hole, similar to how wood fibers go around a knot, Fedor Antonov, CEO of Anisoprint, said. “Therefore, our materials are somewhat reminiscent of natural objects created from synthetic components.

Ultimately, this structural optimization results in products that are twice as strong and half as light as aluminium, at a comparable size. This opens up huge opportunities for the use of composite 3D printing in aviation and other areas that require the maximum reduction in weight of parts while maintaining their rigidity .

According to Alexander Gromov, Professor of the Department of Nonferrous Metals and Gold, NUST MISIS, high strength and low weight are really very important for materials. However, to fully compare the new composites with metals, many tests will still be required, which should show their properties such as resistance to abrasion, fatigue loads and chemicals .

- At the same time, today we can say that Russian specialists have solved the main problem - they have selected the formulation of the starting materials necessary to place carbon fiber in plastic in the 3D printing process. This is a significant result, since with the help of additive technologies it is possible to create parts of such a shape that cannot be achieved by casting,” Alexander Gromov added.

At the same time, according to other experts, the 3D printing method proposed by Anisoprint also has its drawbacks.

- In the new printer, carbon fiber is fused into plastic inside each layer of the part, which increases their internal resistance to mechanical stress. However, these layers are laid parallel to each other and are held together only by a binder polymer, the strength of which is limited,” explained Artem Avdeev, director of the innovative company StereoTek. — Mechanical resistance can be improved by intertwining composite layers inside the parts, making the structure of the material voluminous — this will make it possible to advance even further in the process of improving the mechanical characteristics of products and expand their applicability.

Currently, prototypes of the new printers have entered the market. In particular, the first samples of technology are working at the research center of the BMW automobile company, the Technical University of Munich and the Central Research Institute for Special Machine Building (specializes in the creation of rocket technology).