Carbon fiber composite material has high specific strength and specific rigidity. It is a composite material formed by carbon fiber or carbon fiber fabric as reinforcement and resin, ceramic, metal, cement, carbon or rubber as the matrix, and the lightweight effect is very obvious. , widely used in aerospace, automobile industry, and military products. However, it is difficult to cut carbon fiber composite materials. Based on the experience of Halnn Superhard in research and development of diamond tools for many years, this paper mainly describes how to choose a tool to solve the drilling problem of carbon fiber composite materials.
1.
The classification of carbon fiber composite materials
Carbon fiber composites can be classified in the following two aspects:
(1) According to the mechanical properties of carbon fiber, it can be divided into four types: high modulus, ultra-high modulus, high strength and ultra-high strength. Commonly used are carbon fiber reinforced resin composites (CFRP), carbon fiber reinforced ceramic matrix composites, carbon/ Carbon composite materials, carbon fiber reinforced metal matrix composite materials, etc.
(2) According to the type of raw silk, it can be divided into polyacrylonitrile-based carbon fiber (PAN), cellulose-based carbon fiber (viscose-based carbon fiber), pitch-based carbon fiber, phenolic-based carbon fiber, etc.
2. Problems and difficulties in drilling carbon fiber composite materials
Why is it difficult to drill holes in carbon fiber composites? This is because the carbon fiber composite material is a two-phase or multi-phase structure composed of a soft and viscous matrix mixed with fibers with high strength and hardness. Its mechanical properties are anisotropic, and the hardness of carbon fiber is very high. The machining conditions are relatively poor, the interlayer strength is low, and defects such as delamination and tearing are easily generated under the action of cutting force during the drilling process, especially when drilling, and it is difficult to ensure the processing quality, which is a typical difficult-to-machine material. The difficulties of drilling carbon fiber composite materials are:
(1) During the drilling process, the temperature is concentrated in a very narrow area near the cutting edge, resulting in serious tool wear, low durability and high production costs.
(2) Delamination of carbon fiber composite materials occurs. Delamination will seriously reduce the performance of the material and the processing quality of parts. Even a small delamination is a very serious safety hazard, and even the parts are scrapped, which seriously affects the yield of the product.
(3) The dimensional accuracy and surface roughness of the drilled holes are not easy to meet the requirements, and residual stress is easily generated.
(4) Cutting chips are black dust, which is easy to pollute the environment and endanger human health; in addition, the conductivity of cutting chips can easily short-circuit electrical equipment and power grids.
3. Halnn Superhard's solution for the difficulty of drilling carbon fiber composite materials
(1) Improve the material of the drill bit and improve the wear resistance of the drill bit. Such as polycrystalline diamond (PCD) drill bits, diamond coated tools, etc. Experiments have shown that diamond drills are better than other types of drills, and diamond tools are the best choice for drilling CFRP carbon fiber reinforced composite materials. Or use special drills, such as center drills, twist drills, drill reamers, etc., to achieve high-speed and high-precision drilling, which greatly improves the service life of the drill.
(2) Choose the appropriate drill type
When drilling carbon fiber composite materials, try to choose the appropriate drill type. Reduce the length of the chisel edge, increase the relief angle of the cutting part of the drill, and improve the sharpness of the cutting edge. The drill tip of the drill bit for drilling carbon fiber composite materials should have a certain edge inclination angle, and the edge inclination angle is negative, which can effectively prevent the occurrence of drilling defects.
(3) Use a reasonable process
In the case of high drilling precision requirements, the reaming process or diamond grinding head is used to grind the hole after drilling, which can effectively reduce the surface roughness of the hole and improve the roundness of the hole.
4.
Halnn superhard carbon fiber composite drilling tools
The carbon fiber composite drilling tools developed by Halnn Superhard include: diamond drill bits, diamond drill reamers, diamond twist drills, diamond step drills and non-standard diamond drill bits, etc. The imported PCD sheet is used as the cutting edge, which has good durability Grinding performance, using tungsten carbide as the base, the cemented carbide base has good rigidity and dimensional accuracy, which can ensure the machining quality of drilling and milling, and the internal cooling (internal spiral cooling) channel is designed to improve the cooling performance. The type chip flute can improve the chip evacuation performance, thereby improving the processing efficiency, which is very important for the drilling of carbon fiber composite materials.
Halnn super-hard carbon fiber composite drilling tools can be designed with multiple cutting edges, and the angle and sharpness can be adjusted according to the specific processing conditions. When drilling holes in composite materials, the cutting force of the drill bit can be reduced to avoid material delamination , the sharp cutting edge can ensure the good quality of the hole; the drilling, reaming and countersinking integrated tool, drilling and countersinking are completed at one time, eliminating the need for retraction, tool change and indexing when machining with conventional drills and reamers. Greatly improve processing efficiency.