There are two main reasons for the delamination of carbon fiber plate hole processing: one is the axial force, and the other is the heat generated during the cutting process. Carbon fiber plate hole processing delamination is often caused by the combination of these two reasons, of which the role of axial force is the main one. When the axial force acts on the surface of the carbon fiber plate, if the internal stress generated between the fiber layers reaches or exceeds the bonding strength of the resin between the fiber layers, the fiber layer will be delamination due to the fracture of the resin.
From the analysis of carbon fiber force in the hole processing process, the trajectory of the tool center during drilling processing is a straight line, the cutting rate is 0, and the material is only an axial extrusion force, which is easy to cause the delamination of carbon fiber materials. In the process of helical milling of carbon fiber plates, the trajectory of the tool center is a helix. The center of the tool no longer coincides with the center of the workpiece, but constantly changes along the helix, then the material at the center of the workpiece will be cut off by the tool instead of cracked under the action of extrusion, thereby greatly reducing the action of axial force.
The most serious part of the delamination phenomenon during drilling processing is at the exit, and there is no delamination at the exit during milling, but there is a slight delamination phenomenon at the population. Delamination at the outlet is mainly caused by axial forces, while stratification at the population is mainly caused by shear stress. In the test, it can be seen that the axial force during milling is much smaller than that during drilling. Therefore, when milling the hole, the material can be avoided before entering the cutting zone and being destroyed first, so as to effectively avoid the occurrence of material delamination, tearing and other defects.
When the drilling inlet defect is mainly burr, the outlet defect is mainly delamination; The inlet defects of spiral milling holes are mainly delamination, and the outlet defects are mainly burrs. Compared with drilling processing, spiral milling has less burrs on the hole surface and less tearing phenomenon, and because the axial force is relatively small, the delamination phenomenon is manifested as slight cracks, so the hole processing quality is relatively high.
The drill can only machine holes with the same aperture as the outside diameter of the tool, while the milling cutter can mill holes with different bore diameters. This reduces the amount and variety of tools in stock and reduces machining costs. It can be seen that the use of spiral milling method is feasible for carbon fiber plate hole processing, and the quality is higher than that of conventional drilling.