碳纤维增强复合材料切削加工技术及其应用研究

发布时间：2018-08-19 20:03

【摘要】：由于碳纤维增强复合材料(CFRP)具有比强度高、比模量大等优异性能,在航空航天、国防行业具有广泛的应用前景。复合构件成型后,往往需要根据装配要求进行二次加工,然而,在碳纤维增强复合材料加工中易出现毛刺、分层等加工缺陷,以及刀具磨损等问题。论文以弹托主要表面的加工应用为研究对象,围绕加工机理、刀具磨损、刀具材料和结构、加工工艺参数等影响因素对CFRP材料的加工进行了试验研究和理论分析。以碳纤维增强复合材料的铣削加工为研究对象,通过试验观察,对CFRP材料的切削加工机理进行了研究。结果表明:在工件平放铣削方式下,切屑的典型类型主要有块状切屑和卷曲状切屑;在工件立放铣削方式下,切屑的典型类型主要有长条状切屑;在实际铣削加工中采用逆铣的铣削方式能减小加工缺陷;在切削过程中,纤维呈脆性断裂,纤维所受应力不同,将形成不同的纤维断口形貌,主要的断口形貌有光滑平面断口、倾斜断口、多阶平面断口、不规则断口、波纹状断口,以及长斜面和不规则状断口组合而成的断口等。采用硬质合金(YG6X,未涂层)及其DLC涂层立铣刀,以及钎焊PCD刀片立铣刀分别进行CFRP材料的铣削试验,分析了它们的磨损特征和磨损机理。结果表明,这三种刀具均出现磨粒磨损和树脂粘附等磨损形态,而涂层剥落和成块剥落破损分别为DLC涂层刀具和PCD刀具的特有磨损形态。此外,CFRP材料的钻铣试验结果表明,DLC涂层刀具和PCD刀具均为CFRP材料切削加工的理想刀具。使用不同结构的钻头进行钻削加工试验,结果表明,当钻头直径超过10mm时,制孔缺陷和钻削轴向力均呈大幅增大;采用多刃尖钻和匕首钻钻削CFRP材料时,孔出口制孔缺陷有明显减小,其中匕首钻的最小。为进一步了解匕首钻的钻削过程,还建立了匕首钻的钻削模型及其临界轴向力模型,分析了孔出口缺陷的形成过程,揭示了孔出口缺陷较小的原因,并且获得了分层产生和扩张的临界轴向力值。通过CFRP材料的铣削试验,分析了刀具材料、刀具结构和铣削方式等对切削力和加工缺陷的影响,优化了铣削加工的工艺参数。以减小铣削力和铣削分层因子为目的,切削速度Vc、进给量f和铣削深度αp分别在63～109m/min、0.02～0.18mm/r和1～3mm下,采用PCD立铣刀对CFRP材料进行正交试验,获得了切削速度Vc、进给量f和铣削深度αp的最优组合,即分别为63m/min、0.02mm/r和1mm。为考察齿槽的切制过程和加工缺陷,采用T型铣刀对CFRP材料进行齿槽加工试验,从理论分析和试验研究两个方面,分析了齿槽加工缺陷的形成过程及其变化规律,获得了齿槽加工每齿进给量的合适范围。在此基础上,通过进一步的齿槽加工试验,分析了刀具材料、刀具结构、铣削方式和工艺参数等对齿槽加工缺陷和切削力的影响。针对CFRP复合构件的加工进行试验,确定了车削、镗削和孔内齿槽加工的工艺参数(切削速度Vc、进给量f和背吃刀量αp),获得了孔内齿槽加工刀片和走刀路径的合理方案。至此,在钻、铣、车、镗等加工研究的基础上,通过拟定的加工工艺路线,完成了复合构件120°夹角侧面、端面、外圆、深孔和孔内齿槽的加工。在CFRP复合构件的加工过程中,刀具使用性能和加工质量均能得到有效保障。
[Abstract]:Carbon fiber reinforced polymer (CFRP) has a wide range of applications in aerospace and national defense industry because of its high specific strength and modulus. In this paper, the machining mechanism, tool wear, tool material and structure, processing parameters and other influencing factors of CFRP material are studied experimentally and theoretically. The milling process of carbon fiber reinforced composites is studied. The cutting mechanism of CFRP material is studied by experiment and observation. The results show that the typical types of chips are block chips and curly chips in workpiece horizontal milling, strip chips in workpiece vertical milling, and reverse milling in actual milling. In the cutting process, the fiber is brittle fracture, and the stress of the fiber is different. The main fracture morphologies are smooth plane fracture, inclined fracture, multi-level plane fracture, irregular fracture, corrugated fracture, long inclined fracture and irregular fracture. The milling tests of CFRP materials with cemented carbide (YG6X, uncoated) and its DLC coated end milling cutters and brazed PCD insert end milling cutters were carried out respectively, and their wear characteristics and wear mechanism were analyzed. In addition, the results of drilling and milling experiments on CFRP materials show that both DLC coated and PCD tools are ideal tools for cutting CFRP materials. When drilling CFRP material with multi-edge point drill and dagger drill, the hole-making defect at the exit of the hole is obviously reduced, and the dagger drill is the smallest. The critical axial forces for delamination generation and expansion are obtained. The effects of tool material, tool structure and milling method on cutting force and machining defects are analyzed by milling experiments of CFRP material. The milling process parameters are optimized. The cutting speed Vc, feed F and milling factor are used to reduce the milling force and delamination factor. The optimum combination of cutting speed Vc, feed F and milling depth alpha P was obtained by orthogonal test of CFRP material with PCD end milling cutter at the depths of 63-109 m/min, 0.02-0.18 mm/r and 1-3 mm, respectively. In order to investigate the cutting process and machining defects of groove, the T-type milling cutter was used to carry out tooth cutting of CFRP material. In the groove machining experiment, the forming process and changing rule of groove machining defect are analyzed theoretically and experimentally, and the suitable range of feed per tooth is obtained. Based on the experiments of machining CFRP composite components, the technological parameters of turning, boring and groove machining in the hole (cutting speed Vc, feed F and back feed alpha p) are determined, and the reasonable scheme of groove machining insert and tool path in the hole is obtained. Through the proposed processing route, the processing of 120 degree angle side, end face, outer circle, deep hole and inner groove of CFRP composite component is completed.
【学位授予单位】：南京理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB332

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