A study of hole drilling in Kevlar composites

Kevlar composite materials are difficult to machine due to their anisotropy, high fiber tensile strength, low interlayer shear strength, and poor thermal conductivity, leading to various defects, including material delamination, splintering, fraying, rough surface of the hole, and dimensional shrinkage. This article suggests some technical measures to improve machining quality.

Article source: Composite Material online

  Kevlar composite materials are difficult to process due to their anisotropy, high fiber tensile strength, low interlayer shear strength, and poor thermal conductivity. This means that processing a large number of fastener holes on composite components can lead to various defects, including material delamination, splintering, fraying, and rough surface of the hole, and dimensional shrinkage. All of these can affect the connection strength of the composite material and cause potential accidents. To improve the hole processing quality of Kevlar composite material, it is necessary to consider the organization structure and physical and mechanical properties of the material, as well as the practicability and economy of processing technology. Unlike metal material processing, the processing mechanism of Kevlar composite materials is completely different. A clever design of drilling process equipment is needed, including a clamping device to apply a certain pre-pressure to the composite drilling area and the surrounding materials to improve the stiffness of the drilling area and the surrounding materials. This will improve the cutting ability of the composite material and prevent wire drawing and hair drawing. Reasonable design of tool geometric angle parameters and appropriate cooling lubrication method are also important factors to guarantee improved processing quality. For Kevlar composite material through hole drilling technology, it is recommended to apply a certain pre-pressure to the material through the process device to improve the machinability, instead of using heat treatment methods as with metal materials. The process unit is the key to ensuring the drilling quality of Kevlar composites, with its function being to apply pre-pressure to the drilling area and surrounding materials of the composite material through the ring press block and the upper press plate. The upper press plate and the lower support plate also play a role in improving the drilling and drilling conditions of the material and preventing the material from rising, yielding, and stripping. Machining experiments show that the process device, especially through the uniform pressure of the ring block, plays a decisive role in improving the drilling quality of the composite material. By following these technical measures, satisfactory results can be achieved, which will lay a good foundation for the promotion and application of new materials.

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