Learn about carbon fiber thermoplastic composites in one article

1. Overview of carbon fiber thermoplastic composites

Carbon fiber (CF) is made of organic fibers by high temperature carbonization in an inert atmosphere, which has the characteristics of high strength, high specific modulus, excellent thermal performance and chemical stability, as well as damping, shock absorption and noise reduction, and is an excellent reinforcement material. Compared with traditional thermoset composites, thermoplastic composites have the advantages of short molding cycle, low chemical toxicity, high toughness, impact and damage tolerance, long storage life of prepreg, and strong mass production capacity. The thermoplastic composite with CF as reinforcement combines the performance advantages of CF and thermoplastic resin, and does not undergo chemical cross-linking after molding, and can be melted and reformed for the second time, which is convenient for the recovery and recycling of materials, and solves the problem of treatment of thermosetting CF materials after the expiration of service life.

Thermoplastic resin-based carbon fiber composites belong to crystallization and glass transformation during processing, while thermosetting resin-based carbon fiber composites undergo cross-linking and curing reactions. From the perspective of process difficulty, thermoplastic carbon fiber composites are more difficult to infiltrate than thermosetting carbon fiber composites in the preparation process, but at the same time, the advantages are also obvious: they have the advantages of short molding cycle, good impact resistance, weldability, secondary molding, and high degree of freedom in structural design.

The various parts made of carbon fiber reinforced thermoplastic composite materials have the advantages of low density, high strength, high toughness and high price ratio, and can be recycled and reused, and have a wide range of application prospects in aerospace, military industry, high-end machinery, medical and other fields.

2. Advantages of carbon fiber reinforced composites

Carbon fiber reinforced composites, unlike other FRP composites that use traditional fibers, such as glass fibers or aromatic polyamide fibers, CFRP composites have excellent properties including:

Lightweight – Traditional glass fiber reinforced composites use continuous glass fibers with a content of 70% (weight glass/total weight) and a density of typically 0.065 pounds per cubic inch.

High strength – Despite their low weight, CFRP composites have higher strength and hardness per unit weight than glass fiber composites. This advantage is even more pronounced when compared to metallic materials. For example, experience tells us that CFRP material weighs only 1/5 of steel at the same strength compared to steel. One can imagine why all car manufacturers are looking into using carbon fiber instead of steel to improve the performance of their products.

When CFRP composites are compared to aluminum, one of the lightest metals, the basic assumption is that aluminum of the same strength weighs about 1.5 times that of a carbon fiber body.

3. Case of carbon fiber reinforced thermoplastic composites

The commonly used resin matrices for carbon fiber reinforced thermoplastic composites are: polyetheretherketone PEEK, thermoplastic polyimide TPI, polyphenylene sulfide PPS, polyetherketone ketone PEKK, etc. The following is a brief introduction to the selection of carbon fiber reinforced thermoplastic polyimide, carbon fiber reinforced polyphenylene sulfide and carbon fiber reinforced polyetheretherketone.

 
Carbon fiber-reinforced thermoplastic polyimide (PI) composites

As a new generation of high-performance special engineering plastics, thermoplastic polyimide not only retains the characteristics of traditional thermosetting polyimide such as high strength, high temperature resistance, chemical corrosion resistance, good dielectric property and radiation resistance, but also has outstanding advantages in toughness and hot processing molding.

The addition of carbon fiber can significantly improve the mechanical properties of thermoplastic polyimide, and when the volume fraction of carbon fiber reaches 30%, the tensile and flexural strength of the material is about 2-3 times that of pure resin. Carbon fiber reinforcement also imparts thermoplastic polyimide with improved thermal and mechanical properties, making it a high-performance material with a higher level of wear and corrosion resistance.

Carbon fiber-reinforced polyphenylene sulfide (PPS) composites

Polyphenylene sulfide is also one of the thermoplastic resins favored by the composite industry, which has excellent mechanical properties, corrosion resistance, self-flame retardancy, etc., so it is often used as a matrix material for various high-performance composite materials. The mechanical properties of carbon fiber reinforced polyphenylene sulfide composites are also affected by the carbon fiber content, and the larger the carbon fiber content at a certain threshold, the stronger the ability to bear external loads. Experiments show that the ILSS of continuous carbon fiber reinforced PPS composite panels can still show good stability under the condition of temperature difference of up to 100°C.

Carbon fiber-reinforced polyetheretherketone (PEEK) composite

Polyetheretherketone has high rigidity, good dimensional stability, small linear expansion coefficient, can withstand great stress, will not produce obvious extension due to the extension of time, and its density is small, the processing performance is good, and it is suitable for parts with high requirements for fineness. Polyetheretherketone itself is one of the thermoplastic resins with good heat resistance, and the long-term working temperature can even reach 250 degrees Celsius, and its mechanical properties are basically not affected in such a high-temperature environment. The use of carbon fiber as a reinforcement can further improve the performance of polyetheretherketone materials in terms of strength, rigidity and wear resistance, and also has a significant effect on the overall service life of the product. Relevant experiments show that when the proportion of carbon fiber material is 25%-30%, the wear resistance of composite materials with polyetheretherketone as matrix is significantly improved, and the addition of carbon fiber materials can effectively improve its application value and application range.

4. Future development of carbon fiber reinforced thermoplastic composites
 

In the next few years, the carbon fiber reinforced thermoplastic composite industry will show the following trends:
 

4.1 the demand for lightweight promotes the growth of the proportion of applications

Industries ranging from aerospace to industrial manufacturing are looking for innovative ways to reduce excess weight while reducing weight while providing comparable safety and reliability for functional integration and weight reduction. For example, a car equipped with an electric drive or fuel cell engine can increase its cruising range by reducing the weight of structural or powertrain components, the most direct case is the carbon fiber power battery box customized by Zhishang New Materials for automotive equipment manufacturers, which is one-third lighter than the metal box; Heavy-duty, high-load and durable industrial equipment in industrial machinery can achieve lightweight, thin and precise structures by using materials with high strength and better performance, and the carbon fiber rollers provided by Zhishang New Materials for textile, printing, papermaking, lithium battery and other industries can improve production efficiency and reduce energy consumption at the same time, but also obtain optimized results because of the good dimensional stability, chemical corrosion resistance and fatigue resistance provided by carbon fiber composite materials. It has been proved that the lightweight application value of carbon fiber will greatly promote its application proportion in a variety of industries.

4.2  the performance requirements are constantly personalized and diversified

In order to meet the material needs of certain industries for specific projects, carbon fiber composite parts manufacturers need to continuously develop carbon fiber composite materials with specific application properties, such as high temperature resistance, flame retardancy, self-lubrication, electromagnetic wave permeability and other different performance characteristics, so as to expand the application range of carbon fiber composite materials. Moreover, this adaptable application capability of carbon fiber composites will, in turn, lead to equipment upgrades in industrial manufacturing and other fields.

Aviation, rail transit and automobile manufacturing usually consider the safety of passengers when selecting materials, and flame-retardant carbon fiber composites are more suitable for such applications. Some parts of aerospace engineering and special industrial equipment need to withstand high working temperatures, Zhishang New Materials provides customized services for high-temperature resistant carbon fiber composite parts for such equipment, which can withstand different working temperatures of hundreds to thousands of degrees Celsius, while maintaining a low coefficient of thermal expansion; Many industrial equipment requires parts and components to have sufficient wear resistance and self-lubrication, and composite materials such as continuous CF reinforced PEEK developed by Zhishang New Materials have effectively improved the self-lubrication and wear resistance of parts. Moreover, this continuous carbon fiber reinforced thermoplastic composite product can change or adjust the actual performance of the composite material by selecting different kinds of matrix materials, carbon fiber content and adding processes. It can be said that the application demand in industry and other fields has driven the development of carbon fiber composite materials.

4.3  Recyclability will become an important development goal

If we look at it from the perspective of the whole life cycle of materials, thermoset carbon fiber composites will inevitably face challenges. In order to deal with this problem, there are two main solutions now: one is to conduct recyclability research on carbon fiber composites on the current market; The second is to directly use thermoplastic resin base instead of thermosetting resin base, for example, Zhishang New Materials has created a thermoplastic carbon fiber composite parts solution with continuous carbon fiber as reinforcement and medium and high-end thermoplastic resin as matrix. This thermoplastic resin matrix is different from thermoset resin matrix and has the basic conditions for recyclability and reuse.

Today, this emerging continuous carbon fiber reinforced thermoplastic composite manufacturing technology is struggling to catch up with traditional carbon fiber reinforced thermoset composites and is providing higher performance applications for specific users in the aerospace, military, rail transit, intelligent machinery and high-end medical markets.