Carbon Fiber Mat Production Process

 

Carbon fiber and its composite materials are widely used in various fields due to their excellent properties such as high specific strength, high specific modulus, low density, corrosion resistance, and high temperature resistance. PAN-based carbon fiber accounts for more than 90% of the total carbon fiber output due to its good comprehensive performance and simple production process.

 

The form of the fiber preform largely determines the properties of the composite material. The overall needle punching method is a method of using a needle punching machine to needle the embryo to form a three-dimensional needle punching structure.

 

It not only solves the shortcomings of the resin bonding method such as low interlayer shear strength, uneven overall density and performance, but also overcomes the shortcomings of the 3D weaving structure, such as complex process and long cycle. It is a very promising preform preparation method.

 

PAN-based Preoxidized Fiber Needle Mat Was Prepared By The Whole Needle Punching Method.

 

The reaction, thermal behavior and the influence of different process parameters on the properties of carbon fiber needle mat during the carbonization process of preoxidized fiber needle mat were studied by elemental analysis, tensile test, scanning electron microscopy, FTIR analysis, mass density analysis, reaction principle analysis, etc., and the process optimization under laboratory and industrial production conditions was carried out.

 

The research results show that during the low-temperature carbonization process, the uncyclized linear molecules remaining in the preoxidized fiber will undergo partial secondary cyclization and interchain crosslinking reactions.

 

During the high-temperature carbonization stage, the ladder-shaped polymer undergoes crosslinking and aromatic ring formation, and the planes formed by the cyclized units are connected to each other to form a conjugated plane layer of the six-membered ring structure.

 

The carbon-based surface continues to grow with the increase of temperature, and finally a graphite-like structure is formed inside the PAN fiber.

 

 

The factors affecting the density of the mat body during the needle punching process include the needle punching spindle frequency and the moving speed of the traction nip roller. Preoxidized fiber needle mats of different densities can be obtained by adjusting these two parameters.

 

The improvement of the mechanical properties in the Z direction is achieved on the premise of sacrificing part of the mechanical properties in the X-Y direction. During the carbonization process, the fiber shrinks and curls, resulting in a decrease in the strength of the mat.

 

The reduction in fiber diameter also has a certain effect on the performance of the mat. The volume shrinkage of the mat is weaker than the mass shrinkage, while the change in density is consistent with the change in mass.

 

 

After the carbonization temperature reaches 1000℃, the C content in the fiber exceeds 90%, which is a qualified carbon fiber in terms of composition. The choice of carbonization temperature during production can be determined according to actual needs, and it is necessary to weigh the pros and cons between element content and yield and mechanical properties.

 

Using a slower heating rate will make the carbonization reaction more thorough, increase the carbon content, and increase the weight loss of the mat, but the effect of the heating rate on the carbonization mass yield is weaker than the carbonization temperature.

 

Compared with the carbonization temperature, the heating rate has a weak effect on the tensile strength of the carbon fiber needle mat in the X-Y direction. The selection of the heating rate needs to weigh the pros and cons between the element content and the yield. Under the experimental conditions, the holding time is not an important process parameter.

 

However, in actual production, the problem of thermal permeability needs to be considered. The main principle is that the mat obtained by carbonization is uniform in composition and structure. PAN-based carbon fiber needle mat shows good damage resistance and pseudoplasticity.

 

 

Carbon fiber can be compounded with different materials, such as resin, metal, ceramic and other matrices to make structural materials. Among them, the most widely used and easy to make is carbon fiber reinforced epoxy resin composite material, whose comprehensive index of specific strength and specific modulus is relatively good among existing structural materials.