The success of the carbon fiber composite molding process involves many factors, so it is easy to produce quality problems of carbon fiber products in the processing process. In order to ensure the quality of carbon fiber products and prolong the service life of the mold and save raw materials, Suzhou Nuoen Composite Materials Co., Ltd. combined with its own experience in the molding process, summed up several problems that are very easy to occur, and carried out research and optimization. Analysis of the causes of such problems in the molding process of carbon fiber composite materials, the following is a simple summary.

Defects and influencing factors of carbon fiber molded products:

Resin agglomeration, local lack of material, deformation, cracks, bubbles, uneven surface, poor finish, corner strength is too low, local strength decreased significantly, sticky mold, local fiber exposure, demoulding difficulties are often problems in the process of carbon fiber molding, sometimes in a single form, more in the form of coexistence of a variety of defects.

From mold design to demoulding molding, every step in the molding process of carbon fiber products may have a direct impact on the quality of the products. The operation links in each step are listed separately, and it is found that there are the following types that have a greater impact on the quality of the products:

1. Product design;

2. Mold design;

3. Quantity and uniformity of paving materials;

4. Ratio of resin content;

5. Temperature control and pressurization time;

6. Use of release agent.

Effect of process factors on product defects:

Resin accumulation and local material shortage are problems that will occur in the molding process such as paving materials. The main reason for resin accumulation is that the proportion of resin content is too large. When the volatile matter of the material is too large, the material agglomerates or has poor mutual solubility, resin accumulation will also be caused. Even if the above factors do not have deviation, premature pressurization will often cause resin accumulation.

In contrast, the reasons for local shortage of material are obvious. Insufficient feeding, too late pressurization and poor fluidity of the material are the main factors causing local shortage of material. In addition to the pressure time requires many times of experience accumulation, the rest of the factors can be continuously adjusted in the process of paving, so as to greatly reduce the generation of such defects.

Deformation, cracks, bubbles, uneven surface and poor finish are common surface defects of carbon fiber products. Among them, deformation and crack are often related to the initial work of molding and demoulding operation. First of all, it depends on the structural design of the product itself and whether the design of the mold is reasonable. If these two aspects are not reasonable enough, it is easy to cause the molded product to break or warp after demoulding.

Secondly, special attention should be paid to the speed of heating and the control of temperature during demoulding. Too fast heating will cause uneven curing of the product to cause internal stress. After pressing and heat preservation, the temperature should be gradually cooled under pressure. Demoulding operation should be as cautious as possible to prevent damage to the product and mold. However, bubbles, uneven surface and poor finish are all related to the volatile matter content of the material. In addition to the excessive volatile matter of the material, insufficient air release will also produce bubbles. At the same time, the impact on the surface quality of the product caused by excessive use of release agent or low temperature during molding should also be paid attention.

In terms of strength, the defect of carbon fiber products is that the corner strength is too low or the local strength is significantly reduced. If the structural design of the product itself is unreasonable, such as the radius of curvature of the corner root is too small, the strength of the finished product at the corner will inevitably be affected. If the amount of materials required for the product is not accurately calculated when paving materials, resulting in surplus materials, the phenomenon of overlapping materials will be caused at local positions such as corners. Once the materials are agglomerated, the overall strength of the product will be uneven. If the pressure is too early, the reaction degree of the resin itself is low, the molecular weight is small, the viscosity is low, and it is easy to lose under pressure. The probability of resin aggregation or local fiber exposure in the product will be relatively large, which will affect the strength of the whole product.

At the beginning of the selection of molding process should be fully considered the actual operation of the demoulding, to ensure that the design of the product itself has a certain slope, mold design should have a certain taper, with can not be too tight, so as to facilitate the demoulding. Secondly, the use of release agent should not be too much, but the coating must be uniform, otherwise it will not only affect the surface finish of the product, but also hinder the release. Of course, the more important thing is the appropriate material quantity, temperature and pressure. The appropriate temperature can ensure sufficient curing. The appropriate material quantity and pressure control can ensure the standardization of the size and strength of the finished product. These also determine whether the finished product can be demoulded smoothly.

In a word, carbon fiber molded products involve many process elements. Nuoen compound materials emphasize that products of different specifications, shapes and uses have different parameters in different process links. Therefore, the quality of carbon fiber molded products depends on rich manufacturing experience. Only on the basis of a considerable number and category of production can a better process production standard be formed.

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