In the design and manufacture of carbon fiber reinforced composite UAV, the requirements of structural elasticity and stiffness distribution are often achieved by adjusting the laying angle and the number of material layers.
Carbon fiber reinforced polymer (CFRP) is one of the most widely used reinforcement materials for unmanned aerial vehicles (UAVs). The following three molding processes are generally involved in the production of UAVs using CFRP:
Autoclave forming process
Autoclave molding is one of the high-performance molding processes for composite materials. For UAVs with high speed requirements, its composite components and main load-bearing components are mostly manufactured by this process.
The carbon fiber rod composite component formed by autoclave has better internal quality, more uniform resin content and better mechanical properties.
However, the autoclave forming technology also has some shortcomings, such as high requirements for equipment, high initial investment and processing costs, and relatively poor economy. From the perspective of cost, low temperature and low pressure forming technology is often chosen to replace it when the budget is limited.
In addition, the resin flow, heat transfer, chemical crosslinking and void formation of carbon fiber rod composites in the autoclave molding process will affect and interact with each other, which will increase the difficulty of process control. Once a mistake is made, processing defects such as poor glue and high porosity will appear.
In order to ensure the quality of carbon fiber reinforced composite UAV components, we can well control the pressure and temperature curve of autoclave process by simulating the dynamic changes, resin flow and heat transfer in the autoclave forming process.
Vacuum bag forming process
Compared with the autoclave process, the vacuum bag forming process is relatively simple, and does not need too much investment in the early stage, and the operation difficulty is moderate. However, the pressure of this forming method is small, and it is only applicable to composite components with low quality requirements. It is mainly used to manufacture honeycomb sandwich structures and laminate structures that are not more than 1.5mm.
Because of the obvious cost advantage, this process method is widely used in the manufacturing of low-speed UAV, because in the manufacturing of small low-speed UAV, the vacuum bag forming technology can meet the production requirements of most parts.
In practical operation, prepreg paving, wet paving and other processes are required for vacuum bag forming, and the wet operation is affected by human factors, which is easy to lead to uneven coating of the glue, which is particularly obvious in the formation of sandwich structure.
In addition, the unreasonable brushing direction can also easily lead to the bending and change of the fiber direction, threatening the stability of carbon fiber rod composites. Our new material technology adopts prepreg paving, which can effectively avoid the above problems and improve the stability of the parts.
compression molding
The molding process is more suitable for the manufacture of foam sandwich composite components. It combines the advantages of autoclave molding technology and vacuum bag molding process. It has high production efficiency, high molding pressure, moderate equipment investment and cost, and good economy.
This molding process is mostly used in the parts of UAV rudder surface with foam sandwich structure. In the manufacturing of carbon fiber rod UAV wing plate, the molding process can also ensure the appearance quality and wing shape accuracy of UAV wing, and improve the overall manufacturing quality of UAV.
However, pressure control is the key process of the process. Through the structural analysis of products and the summary of long-term experience, our new materials can more accurately determine the pressure control parameters and ensure the performance level of structural parts.