Research On Hole Making Technology Of Composites With Narrow Deep Cavity Under Stiffness Constraint

With the increasing demand of lightweight and high performance in aerospace and defense military,fiber reinforced composites have been widely used in many critical products.However,due to their anisotropic characteristics,composites are difficult to be processed,especially for the hole making of large composite structures with narrow deep cavity.As the processing characteristics are in the narrow cavity,the tools cannot reach the processing area,the narrow inner space of composite structures also limits the volume of the processing equipment,thus leading to the equipment in low stiffness.On the other hand,due to the high hole making force and complex processing characteristics,the hole making process cannot be implemented by existing automation equipment but be done manually,resulting in processing quality and processing efficiency difficult to guarantee.Being aimed at the low stiffness constant problems of composite structures with narrow deep cavity,fiber reinforced composites are taken as research object in this paper,and based on the mechanism of processing,the change rules of cutting force are analyzed to help seeking the low cutting force hole making technology suitable for composites.Moreover,the automatic hole making machine suitable for narrow deep cavity structures under low stiffness constraint is developed to realize automatic hole making with high quality and efficiency.The main research works of this paper are as follows:(1)Based on the current study of composite processing mechanism and methods,the material failure form and chip formation principle under different paving angles in the cutting process are analyzed,the mechanism as well as the change rules of the machining cutting force are found.By analyzing machining principle and chip form of the orbital hole making process,the change rules of its cutting force are obtained.Based on the mechanism of chip formation and material breakage in composite processing,the concept of ‘micro-edge cutting'is introduced,and based on this concept,hole orbital grinding method is provided by usingelectroplated diamond tool.(2)To analyze the change rules of cutting force caused by the carbide drill,the PCD drill,the carbide milling tool and the electroplated diamond grinding tool in hole making process,the experiments on different hole making processing methods are carried out,which proves that the hole orbital grinding method have the advantage in reducing the cutting force.In addition,the influence of different cutting parameters on cutting force is also investigated to find the appropriate range of parameters under low stiffness constraint and verify the high adaptability of the hole orbital grinding method.(3)Based on the structural characteristics and processing requirements of composite structures with narrow deep cavity,the design of automatic machining scheme and equipment for the narrow deep cavity composite structure are implemented.Based on the characteristic of narrow deep cavity and the research of low cutting force hole making technology,the detailed design of the machining system is carried out.To lighten the machining system,the weight reduction optimization and simulation verification of the processing device platform are accomplished.The scheme and equipment provide theoretical and technical support for the actual production of narrow deep cavity structures.