Is carbon fiber a composite material? What is its relationship with composite materials?

Carbon fiber is not a composite material; it is an inorganic high-performance fiber material with a carbon content of up to 90%. Carbon fiber is a single material, whereas composite materials are composed of carbon fiber plus a matrix. For example, a popular carbon fiber bicycle is made of carbon fiber-reinforced resin composites. In addition, glass fiber, aramid fiber, and boron fiber can all serve as reinforcements, such as fiberglass, which is a composite material made of glass fiber and resin. 

As the 'skeleton' of composite materials, carbon fiber has significant application value in aerospace manufacturing in China. Carbon fiber-reinforced polymer composites (CFPR) are used in airplane wings. On December 15, 2009, the Boeing 787 successfully completed its test flight, with 50% of its fuselage made of composite materials. The value of carbon fiber is primarily realized through composite materials; the two are interdependent, jointly promoting the development of high-end manufacturing and technological innovation.

Although single carbon fiber has excellent performance, in practice, it exists in a discrete fiber state and cannot be directly used as a structural material. It requires a matrix material such as epoxy resin to bind the carbon fibers into a whole, forming sheets, tubes, or curved structures for convenient use. However, during production, improper operations, such as incomplete fiber layer adhesion to molds or local accumulation, can lead to fiber buckling in wrinkled areas during use, reducing load-bearing capacity. Under special service conditions, internal cracks, delamination, and other defects can easily occur, severely shortening the service life.

Carbon fiber-reinforced polymer composites (CFRP) are prone to various defects during production due to material characteristics, process control, or environmental factors. These defects directly affect the mechanical properties and service life of the materials. Non-destructive testing equipment, such as scanning acoustic microscopes, can be used to detect them, reducing errors caused by manual visual inspection and ensuring the reliability and consistency of composite material parts.

A scanning acoustic microscope (SAM) is a type of acoustic testing equipment that uses water as the coupling medium and sound waves as the detection signal. It receives reflected and transmitted signals through a high-frequency ultrasonic transducer and constructs two-dimensional C-scan images using specialized software. The system is used for non-destructive testing of carbon fiber composites, resin-based composites, flat, standard curved surfaces, DOT cylinders, and other structures. It can automatically scan defects such as delamination, inclusions, cracks, and porosity. The system equipment includes an ultrasonic host, software, motion control unit, water tank and circulation unit, and sensors. It features an X, Y, Z, A four-axis linked motion control system, with the A-axis serving as the probe swing axis or roller axis (suitable for cylinders), enabling standard curved surface tracking scanning. The scanning system can not only automatically store data during scanning but also display real-time A-, B-, C-, T-, and 3D ultrasonic images of the tested materials.

Almost the entire downstream carbon fiber industry is used for composite material production. According to statistics, about 90% of global carbon fiber is used to prepare resin-based composites, with the remaining portion applied in thermal materials, electrodes, and other specialized fields. Therefore, the demand for carbon fiber composites (CFRP) remains enormous. ...

The downstream of the carbon fiber industry is almost entirely used for composite material production. According to statistics, about 90% of carbon fiber worldwide is used to prepare resin-based composites, while the remaining portion is used in special fields such as thermal materials and electrodes. Therefore, the demand for carbon fiber reinforced polymer (CFRP) composites is still enormous. The quality of products on the market varies, and only proper quality inspection can help many production enterprises stand out. Non-destructive testing equipment, such as immersion ultrasonic scanning microscopy (SAM), can help technicians detect internal defects in composites and improve production efficiency and quality standards for enterprises.