The carbon fiber composite material molding process is to put a certain amount of prepreg after a certain pretreatment into the mold cavity, apply a certain pressure to make the prepreg fill the mold cavity, and under a predetermined temperature condition, the prepreg is in the mold cavity It gradually solidifies inside, and then the carbon fiber composite material product is taken out from the mold, and then the necessary post-processing is performed to obtain the final carbon fiber composite material product.

The previous article introduced the processing flow of carbon fiber composite material compression molding. From this we can know that the final product molding factors include prepreg, hot press, working mold, working environment, site temperature, relative humidity, etc., the most important of which is prepreg The process of curing into a product in the cavity after the mold is installed is the result of the combined effect of pressure, temperature and holding time. Here we focus on analyzing the influence of pressure, temperature, time, volatiles and other factors on the molding process.

1. Molding pressure

Pressure can accelerate the flow of prepreg in the mold cavity, increase the density, overcome the pressure generated by the low-molecular substances released during the polycondensation reaction of the resin matrix, and avoid swelling and delamination. At the same time, the mold pressure can also close the tooling mold and the product It has a fixed size and prevents deformation during cooling.

The molding pressure depends on the type of prepreg, the shape of the product and the state of the prepreg. If the fluidity of the prepreg is smaller, the curing speed is faster and the compression rate is larger, the pressure required is also greater; otherwise the pressure required is smaller. In the molding process of molded products, temperature and pressure are interrelated. Increasing the mold temperature can increase the fluidity of the prepreg. For example, reducing the molding pressure from the beginning of the molding to the maximum fluidity can also achieve the desired purpose.

2. Temperature

The flow, filling, and curing reaction speed of the prepreg in the molding process are closely related to the temperature, and the temperature plays a major role in the molding process, which affects the degree of crosslinking of the resin matrix, and thus also affects the composite material. The final performance of the product.

The practice table also shows that increasing the mold temperature can accelerate the curing speed and shorten the curing time, but excessively high temperature will cause the prepreg to cure the dissatisfaction due to the fast curing speed and the rapid decrease in fluidity, especially the large thin wall, For composite products with complex shapes, when the temperature is too high, the outer layer of the product cures much faster than the inner layer, which makes it difficult to remove the volatiles in the inner layer, which reduces the physical and mechanical properties of the product, and also causes defects and deformations. When the curing temperature is too low, the curing temperature is slow, and the phenomenon of low curing degree may occur.

3. Molding time

The molding time is related to the type of prepreg, volatile content, product shape, thickness, tooling mold structure, molding temperature, pressure and other factors. The length of the molding time greatly affects the performance of the product. The molding time is too short, the curing is incomplete, the physical and mechanical properties of the product are low, the surface roughness is poor, and the product is prone to deformation. The increase of the molding time can reduce the shrinkage and deformation of the product, but it should be noted that the molding time is too long, the resin cross-linking is excessive, and the internal stress of the product will increase, so choose the appropriate molding time.

4. Volatile matter

During the molding process, the volatile content greatly affects the fluidity of the prepreg. The volatile content is large, and the prepreg fluidity during the molding time is too large. The excessive volatile content makes the prepreg fluidity too large, which causes resin matrix loss, product bubbles, surface roughness and other phenomena, but the volatile content is too low It will also reduce the fluidity of the prepreg, making it difficult to form composite materials.

In the molding process of composite materials, the final inspection is only a judgment of the quality of the product, which cannot be traced back, and the control of each process in the molding process is the key to ensuring the production of qualified products. Each process is strictly monitored to maximize the pass rate of carbon fiber composite products. At the same time, research is conducted on the performance and reliability requirements of carbon fiber products, and we are determined to provide each customer with the highest quality carbon fiber products.