Study On High Quality Hole Making Of Aramid Fiber Composites

Aramid fiber composites have a series of advantages,such as low density,high specific stiffness,high specific strength,excellent impact resistance and electromagnetic properties,it is widely used in aerospace,weapon armor,electronic industry,automobile and other fields.It is inevitable that aramid fiber composites need to be machined after forming,especially when the components are connected with each other,a large number of holes need to be made.The anisotropy and poor thermal conductivity of aramid fiber reinforced resin matrix composites lead to burr,tear,delamination and burns in hole-making.Cutting damage in hole-making of aramid fiber composites will seriously affect the reliability and service life of the workpiece,and even cause potential safety hazards.This topic is aimed at the AFRP hole damage,through the analysis of material properties and cutting mechanism and experimental exploration,to explore the high-quality hole making process of AFRP.In this thesis,by analyzing the characteristics and cutting model of aramid fiber composites,we can see that there are great differences between matrix and reinforcement fibers due to their different properties,which lead to burr,delamination,tear and burns in hole-making.The above conclusions can be validated by the results of bore-making damage observation with twist drills on aramid test samples.The experiments of drilling and spiral milling for aramid fiber composites show that the cutting force of spiral milling is low and the quality of holes is relatively good.At the same time,the structure and material of milling cutter have a significant impact on the quality of drilling.Measuring the temperature of the cutting zone and analyzing the quality of the hole-making show that when the temperature of the cutting zone is too high,the fibers are easier to be extracted from the resin matrix under the action of cutting force,resulting in hole-making damage.Through the above research,the following hole-making damage reduction strategies are obtained.Spiral milling with external cooling air can effectively reduce the temperature of the cutting zone and inhibit the burning damage of the hole-making for aramid fiber composites.Surface slicing and end milling can effectively restrain the delamination of burrs at the entrance and exit of aramid fiber composites composite holes,and the burns can be effectively restrained when the depth of surface slicing is less than the thickness of two layers of composite materials.The damage of orifice can be improved by adding cushion board in hole-making,but the material of cushion board is an important factor affecting the quality of hole-making,and the effect of carbon fiber cushion board is better than that of wood cushion board.The PCD milling cutter is a high-quality and high-efficiency tool for making holes in aramid composites.It can be obtained after the tool life test.After 120 holes,the tool has obvious chipping.In this thesis,the characteristics and cutting model of aramid fiber composites are analyzed,and the causes of hole-making damage and machinability of aramid fiber composites are explored through experiments.Finally,the high-quality hole-making process of aramid fiber composites is obtained through experiments,which provides guidance and reference for aramid fiber composites in actual cutting process.