With the rapid development of aerospace, automobile industry, medical equipment, electronics industry and other fields, traditional materials can no longer meet the current market demand, which has given rise to the emergence of composite materials. The application of 3D printing technology to the manufacturing of composite materials is also becoming more and more popular. According to the IDTechEx report, the composite 3D printing market size will reach US$1.73 billion by 2030.

Samples 3D printed by continuous carbon fiber.

Composite materials are products made from the combination of two or more different materials. One material acts as a matrix, holding the structure together, while the other acts as a reinforcement, providing additional properties to the product. Among them, fiber materials such as carbon fiber and glass fiber are the most commonly used reinforcement materials, while materials such as thermoplastics (such as ABS or PLA) are often used as matrix materials. Compared with traditional processes such as mold opening, mold sealing and casting for manufacturing composite materials, 3D printing simplifies the manufacturing process to a great extent, reduces manual operations, and also improves the stability of the product.

Continuous carbon fiber 3D printing at work.

In the field of materials engineering, when we talk about composite materials, we usually refer to composite materials with reinforced fibers added. In the field of 3D printing, there are three most commonly used fiber materials, namely carbon fiber, glass fiber and Kevlar fiber. These composite fibers can improve the strength, stiffness, heat resistance and durability of traditional 3D printed parts, greatly expanding the application fields of 3D printing. Next, we will introduce these three most common fiber materials one by one.

Carbon fiber composite material:

Carbon fiber is a material made of interconnected carbon atoms forming a crystalline structure arranged in strands, which provides excellent stability under tension. Due to its excellent strength-to-weight ratio (twice that of aluminum), carbon fiber is known as the "King of New Materials" and has excellent mechanical properties and chemical stability, making it suitable for manufacturing lightweight and strong parts.

Traditionally, thermoset resins are used as adhesives to hold these fibers into the desired shape and cure around the matrix material. In 3D printing, there are two different forms:

Short fibers are added to the filament.

1. Chopped fiber: Cut carbon fiber into thin pieces less than one millimeter and mix it into traditional thermoplastic for printing. The short fibers blend into the entire matrix and strengthen the part, making this material suitable for most 3D printers. Among them, the amount of carbon fiber and the length of the chopped segments will affect the strength and quality of the part.

Continuous fiber reinforced composite wire.

2. Continuous fibers: Continuous carbon fiber reinforced bundles are placed where reinforcement is needed during the printing process. Continuous fiber manufacturing requires two different nozzles, where the continuous fibers are first coated in a curing agent and then placed into a thermoplastic matrix extruded through a secondary printing nozzle. The final fibers form the backbone of the 3D printed part, while the thermoplastic acts as the skin.

Different types of continuous fiber reinforced infills.

Various matrices such as PLA, PETG, nylon, ABS or polycarbonate can become even stronger and lighter with the addition of carbon fiber. However, the amount added can be affected by how and what type of fiber is used. Generally speaking, continuous carbon fiber 3D printing is stronger relative to chopped carbon fiber because the continuity helps spread the applied load.

Typical application

In October 2018, Boeing produced a large 3D printed carbon fiber reinforced composite part for the 777X passenger aircraft, which was 3.6 meters long. The raw material is ABS plastic with 20% carbon fiber added, and is produced using large-scale additive manufacturing equipment and vertical layer printing (VLP) technology, demonstrating the application of 3D printing in the aerospace field.

In a recent case, CLAAS, the No. 1 agricultural machinery manufacturer in Europe and No. 4 in the world, used Markforged’s continuous fiber composite 3D printing technology to manufacture a lifting ring for lifting a 17-ton large locomotive, showing the importance of continuous fibers in the industrial field. potential.

Fiberglass composite

Introduced in 1930, fiberglass is a strong and cost-effective reinforcement material. When used on the appropriate substrate, it can create parts ten times stronger than ABS. Glass fiber composites are less rigid and brittle than carbon fiber composites. In addition, fiberglass has excellent mechanical properties, is very effective as an electrical insulator, and has low thermal conductivity. The material is available in a variety of colors and has low shrinkage, minimizing the risk of part warping.

Fiberglass-reinforced 3D printing filaments have proven valuable for engineering prototypes and final product parts that require strong mechanical properties and heat resistance.

Typical application

In October 2020, Moi Composites manufactured a boat called MAMBO through fiberglass 3D printing, which is 6.5 meters long, 2.5 meters wide and weighs about 800 kilograms. It is the first real ship in the world to be 3D printed using continuous fiberglass thermoset materials. The manufacturing process uses patented continuous fiber manufacturing (CFM) technology, in which a robot deposits thermosetting resin-impregnated continuous fibers layer by layer based on a 3D model, demonstrating the potential of continuous fibers in ship manufacturing.

Kevlar fiber

Kevlar, also known as Kevlar or aramid, was first introduced by DuPont in 1971 and pioneered by Stephanie Kwolek. It belongs to the aramid fiber category and is an extremely durable material that is often combined with a variety of plastics to create composites. Kevlar fiber has excellent tensile strength and fatigue strength and is mainly used to manufacture parts that need to withstand severe vibration and wear resistance.

Kevlar has a strength-to-weight ratio that is five times that of steel and has excellent heat resistance, up to 400°C. In addition, Kevlar has properties such as low density, versatile applications, and uniform molecular structure, which help create high-quality 3D printed parts.

Typical application

A striking example is the use of this composite material to 3D print car parts by Aptera Motors in the United States, highlighting the huge potential of reinforced materials in automotive manufacturing.

Currently, in the 3D printing continuous carbon fiber market, the main players include Markforged of the United States and Anisoprint of Russia. Markforged calls it continuous filament fabrication (CFF), while Anisoprint calls it composite fiber coextrusion (CFC). In addition, Suzhou Tongyi 3D also officially commercialized its domestic continuous carbon fiber 3D printer last year, filling the technical gap in this field.

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