碳纤维增强树脂基复合材料制孔技术研究现状与展望

碳纤维增强树脂基复合材料(CFRP)具有优越的物理和力学性能,已在航空制造工业中得到大量应用。在主承力结构中,CFRP与金属材料的连接通常为机械连接。然而,CFRP的各向异性严重影响了其制孔质量。由于CFRP和金属具有截然不同的材料属性,CFRP/金属叠层结构制孔技术成为飞机装配过程中的一大难题。本文首先阐述了CFRP及其叠层结构在切削过程中的切屑形成机制、钻削力和钻削热的研究现状;其次,剖析了钻削过程中典型加工损伤,如毛刺与撕裂、分层缺陷及孔壁表面损伤的产生原因和影响因素;然后,介绍了CFRP制孔刀具材料和几何结构的优化设计研究进展,并综述了螺旋铣孔、变工艺参数钻削、"以磨代钻"和振动辅助制孔等多种CFRP及其叠层结构加工新技术及钻削过程的仿真研究。最后,借鉴钎焊工具和超声振动技术的独特优势,提出了磨粒有序排布钎焊金刚石工具的超声振动加工构想,以达到CFRP及其叠层结构的精密高效制孔加工这一目的。     

纤维增强复合材料制孔分层缺陷检测与评价技术研究进展

纤维增强复合材料的制孔工序是实现复合材料结构件连接的重要环节,复合材料的各向异性和层间强度低极易导致分层缺陷,而制孔质量直接影响复合材料零部件物理性能的发挥和安全服役中的可靠性。因此,必须对复合材料制孔的分层缺陷进行检测并加以评价,用以优化刀具设计和加工工艺参数。该文在简要阐述制孔分层缺陷产生机理的基础上,首先,重点分析渗透液、光学、渗透X射线、常规超声C扫描、工业CT和超声显微镜6种分层缺陷检测方法的基本原理、特点及研究进展;然后,分类总结制孔分层缺陷的7种定量评价因子;最后,讨论复合材料制孔缺陷在线监测与评价的可行性和所面临的技术挑战。     

碳纤维增强复合材料螺旋铣孔切削力及加工质量研究

针对传统钻孔方法加工复合材料时易导致分层、撕裂等缺陷的问题,采用螺旋铣作为新的制孔技术,根据飞机装配现场的实际加工条件,构建以机器人为移动载体、螺旋铣孔终端执行器为加工单元、螺旋铣孔专用刀具为切削工具的加工系统,采用该加工系统对碳纤维增强复合材料(CFRP)螺旋铣孔关键工艺参数进行正交试验,并讨论了刀具主轴转速、每齿进给量和轴向切削深度等工艺参数对切削力的影响规律;通过对加工缺陷的监测,探讨了切削力与CFRP分层、撕裂等缺陷之间的关系;最后对工艺参数进行优化,经试验验证,优化后轴向切削力较优化前降低26%以上,孔入口及出口处均无撕裂、毛刺,加工质量最优。     

基于划痕试验的碳纤维/环氧树脂复合材料制孔毛刺与撕裂缺陷形成机制

碳纤维/环氧树脂（C/EP）复合材料制孔毛刺和撕裂缺陷,对构件的装配精度影响较大。为了揭示C/EP复合材料制孔毛刺和撕裂缺陷的形成机制,采用微米划痕试验研究沿不同纤维方向切削加工时材料的破坏去除过程,并用FEI公司Quanta 200 环境扫描电镜对划切后的沟槽及切屑的形貌进行观察分析。结果表明：当划切方向与纤维方向垂直时,划切力最大,较易产生撕裂缺陷;当划切方向与纤维方向呈30°、45°和60°时,划痕左侧纤维受到压头挤压向左退让并弯曲,产生锯齿形断裂,否则形成毛刺;划痕右侧纤维为避让压头发生较大的弯曲变形,纤维断裂均匀,不容易形成毛刺。理论分析和划痕试验结果表明：制孔加工时,纤维方向与刀具旋转方向成钝角的区域容易产生毛刺缺陷,与刀具旋转方向成锐角的区域边缘光滑,与刀具旋转方向垂直的区域容易形成撕裂缺陷;出口缺陷与试验结果一致。     

碳纤维/环氧树脂复合材料制孔损伤综合评价方法

碳纤维/环氧树脂(C/E)复合材料在制孔过程中容易产生毛刺、撕裂和分层等多种加工损伤, 对加工损伤进行合理有效的评价是复合材料构件经济性和可靠性的重要保证。针对现有纤维增强复合材料制孔损伤评价方法的单一性和局限性, 首先, 基于统计方法的相对指标法, 提出了综合考虑毛刺、撕裂及分层损伤的C/E复合材料制孔损伤综合评价的新方法, 建立了损伤因子的数学模型。随后, 根据评价指标的关联性, 采用刀具磨损试验确定了数学模型中的所有系数, 以及判别C/E复合材料制孔质量合格与否的临界损伤因子值。最后, 通过超声波探伤对提出的评价方法的准确性进行了验证。结果表明:采用提出的C/E复合材料制孔损伤综合评价方法, 能够有效地反映和评价不同加工参数下的制孔质量状况。      

碳纤维复合材料构件加工缺陷与高效加工对策

碳纤维复合材料钻削加工时易产生分层、毛刺、撕裂等缺陷,是典型的难加工材料。本文以碳纤维增强/树脂基复合材料为研究对象,观察钻孔缺陷形成过程,建立单丝切削模型分析缺陷形成原因;讨论了轴向力对缺陷的影响规律。结论如下:纤维方向对缺陷形成有重要的影响,轴向力增大分层与撕裂缺陷相应增大;以磨代钻加工工艺、新型PCD刀具和螺旋面钻头对于提高碳纤维复合材料钻孔质量都有很大提高。     

基于超细晶硬质合金钻头的AFRP钻削性能

采用超细晶硬质合金钻头开展了芳纶纤维增强树脂基复合材料(Aramid Fiber Reinforce Polymer Composites,AFRP)的钻削实验,从钻削力、钻削温度、制孔质量、刀具磨损等方面对比分析了超细晶硬质合金钻头与普通硬质合金钻头的钻削性能。实验结果表明:芳纶纤维增强树脂基复合材料钻削过程中,钻削力随进给速度的增大而增大,随主轴转速的增大而减小,超细晶硬质合金钻头的钻削力比普通硬质合金钻头降低了40.6%以上;钻削温度随进给速度的增大而减小,随主轴转速的增大而增大,相对普通硬质合金钻头,采用超细晶硬质合金钻头的钻削温度降低了47~85℃;超细晶硬质合金钻头钻削产生的拉毛和热损伤明显少于普通硬质合金钻头;经过长时间的钻削,普通硬质合金钻头的橫刃和主切削刃出现了崩刃,后刀面出现了严重的磨料磨损;而超细晶硬质合金钻头由于高硬度和高耐磨性等特性,刀具的磨损相对较小,适合于芳纶纤维增强树脂基复合材料的高效低损伤加工。     

芳纶纤维增强树脂复合材料液氮冷却钻孔试验

芳纶纤维增强树脂（AFRP）复合材料是一种公认的难加工材料,加工中极易出现毛刺、烧蚀等缺陷,目前缺乏对其有效的加工工艺方法。为提高其加工质量,研究了液氮作为冷却介质的AFRP复合材料钻孔试验。在相同切削参数下进行了干式切削和超低温加工对比试验,测量了切削过程中的轴向切削力和孔临近区域的温度,并计算了孔的进出口毛刺面积和分层因子,分析了AFRP复合材料缺陷的成因,探讨了不同加工条件下缺陷的变化规律。结果表明:与干式切削相比,采用液氮超低温冷却加工的切削力升高了约15.2%,切削温度降低了约141.6℃,毛刺面积减少了约24.7%,因切削热产生的烧蚀现象得到抑制,明显改善了AFRP复合材料的加工质量。      

整体硬质合金刀具表面缺陷非破坏检测方法

针对整体硬质合金刀具磨削裂纹等表面缺陷的无损检测,重点分析和讨论了后乳化型荧光渗透探伤法及其在整体硬质合金刀具质量保障技术领域中的应用情况,并确定了刀具的荧光渗透检测工艺流程和工艺参数。最后对整体硬质合金刀具磨削裂纹等表面缺陷的形态分布规律进行了归纳和分析。     

不烧滑板磨削加工用Fe-Ni-Cu-Sn金属基金刚石工具的制备与性能

Al₂O₃-C不烧滑板作为连铸功能耐火材料在炼钢领域中受到广泛应用,而金属结合剂金刚石工具在滑板磨削加工中起到关键作用。本工作通过热压烧结法制备Fe-Ni-Cu-Sn金属基胎体和Fe-Ni-Cu-Sn金属基金刚石工具,首先研究烧结温度、保温时间和烧结压力对金刚石工具胎体力学性能的影响,获得优化的胎体烧结工艺参数并为后续制备金刚石工具奠定基础;其次研究不同的金刚石磨料对金刚石工具力学性能及磨削不烧滑板性能的影响,通过研究金刚石的浓度、粒度、品级与加工工具磨削效率、寿命及锋利度的关系,从而得到磨削加工不烧滑板的金刚石工具中金刚石磨料的优化参数,通过SEM对金刚石工具表面胎体与金刚石磨料的结合状态、金刚石的磨损情况进行表征。实验结果表明：金刚石工具胎体的最佳烧结工艺参数是烧结温度、烧结压力和保温时间分别为785℃、170 MPa、240 s;金刚石工具中的金刚石磨料最优选择为金刚石浓度25%、粒度45/50、品级SMD35。     

Influence of nozzle design and process parameters on surface roughness of CFRP machined by abrasive jet

Carbon fiber reinforced polymer composites find extensive applications in the areas of automotive, aircraft and aerospace, medical sciences, and electronics. Their usage in automated engineering industry needs good quality in components and excellent surface finish. The aim of this research work is to make holes on carbon fiber reinforced polymer composite material using a newly designed nozzle with and without internal thread. Surface roughness (Ra) was calculated across the depth of the machined hole. The effect of air and abrasive mixture pressure (P), stand-off distance (L), nozzle diameter (D), and abrasive size (S) on surface roughness was carried out for two different nozzles. The experimental result showed offer of good surface finish on CFRP materials from the newly designed nozzle with internal thread.     

Effect of abrasive jet process parameters on machining glass fibre reinforced polymer composite

An experimental and theoretical research work on abrasive jet machining of glass fiber reinforced polymer composite materials was conducted using abrasive jet machining setup fabricated in our workshop. The objective of this research work is to machine holes on the glass fiber reinforced polymer composite using an abrasive jet machine under various levels of process parameter. The material removal rate and hole geometry (kerf analysis) were observed as a part of the investigation. Four factors five levels central composite rotatable design matrix was used for optimizing the required number of experiments. The objective of the present investigation is to develop mathematical models using the response surface methodology. The adequacy of the models has been checked using the ANOVA technique. Use of the developed mathematical models, material removal rate and hole geometry of the machined glass fibre reinforced polymer composite helps prediction at 95% confidence level.     

粉末烧结法和铸造法制备ZrO2增韧Al2O3陶瓷颗粒增强高铬铸铁基复合材料及其耐磨性能

将粒径为1~2 mm的ZrO₂增韧Al₂O₃陶瓷颗粒(ZTA_p)、高铬合金粉末和黏结剂混合真空烧结制备蜂窝状预制体,再浇注高铬铸铁液制备出ZTA_p增强高铬铸铁基复合材料。采用SEM、EDS、XRD分析复合材料的界面微观结构和物相组成,通过三体磨损试验评价复合材料的耐磨性能。结果表明,烧结高铬铸铁基体在铸造过程中发生重熔,与铸造高铬铸铁基体呈冶金结合,ZTA_p与金属基体界面结合致密,无裂纹、气孔等缺陷。复合材料三体耐磨性能达到高铬铸铁的3倍以上。将该复合材料应用于制备磨辊件,经过5 000 h服役,柱状区和复合区在磨辊半径方向上的磨损量分别为8.2 mm、5.9 mm,预计寿命可达到高铬铸铁磨辊的2倍以上。      

Effect of back pressure on the grinding performance of abrasive suspension flow machining

Abrasive suspension flow machining (ASFM) is an advanced finishing method that uses an abrasive suspension slurry for grinding and chamfering as well as the finishing of inaccessible components. This study examines the effect of back pressure on the grinding characteristics of an abrasive suspension flow during the grinding of slender holes. A numerical model was developed to simulate the abrasive suspension flow in a slender hole and was verified experimentally using injector nozzle grinding equipment under different grinding pressures and back pressures. It is shown that the ASFM with back pressure not only eliminates the cavitation flow in the spray hole, but also increases the number of effective abrasive particles and the flow coefficient. Increasing the back pressure during the grinding process can increase the Reynolds number of the abrasive suspension flow and reduce the thickness of the boundary layer in the slender hole. Moreover, increasing the back pressure can improve the flow rate of the injector nozzle and its grinding performance.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-021-00372-z     

陶瓷结合立方氮化硼磨削工具材料制备研究

陶瓷结合立方氮化硼(CBN)磨削工具是一类用于磨削加工的新型陶瓷/玻璃复合材料。本文作者从复合材料制备理论角度探讨了这类材料的制备原则,并进行了试验研究。研究结果表明:CBN磨具的烧成温度以低于800℃为宜;陶瓷结合剂与CBN磨料的热膨胀系数匹配性对磨具强度有较大影响,具有较小热膨胀系数和较高强度的C₁结合剂较适合CBN磨具制备。在一定温度范围内,适当提高烧结温度,有利于提高陶瓷结合剂桥相本身强度及结合剂与CBN磨料颗粒的结合强度。     

Bearing behavior of triaxially braided flat and tubular composites

An experimental study was carried out to evaluate the bearing behavior of glass fiber reinforced epoxy composites made from the triaxial braiding process. The bearing strengths of braided and machined holes in flat as well as tubular samples were compared. The effects of specimen geometry, braid angle, and specimen consolidation condition were investigated. Comparison between specimens with braided and machined holes indicated a higher bearing capacity for the braided joint hole compared with the machined one in tubular specimens whose thickness was not precisely controlled. For flat samples with uniform thickness, the braided hole showed similar or even lower bearing capacity compared with the machined hole, possibly due to the disturbance in fiber arrangement around the braided hole.     

Drilling of Composites Using Tools of Polycrystalline Superhard Materials

The advantages of using tools of polycrystalline superhard materials for drilling workpieces of fiber reinforced composites are shown. The results of a comparative quality assessment of holes produced by high-speed steel drill bits and polycrystalline diamond inserted drill bits are discussed. The polycrystalline diamond inserted drill bits have been found to provide high-quality drilling of fiber reinforced composite materials.     

Experimental Investigation on Rotary Ultrasonic Face Grinding of SiCp/Al Composites

SiCp/Al composites have been widely used in many fields such as aerospace, automobile, advanced weapon system, etc. But this kind of material, especially with high volume fraction, is difficult to machine due to the reinforced particles existing in matrix, which has limited its further application. Rotary ultrasonic machining (RUM) has many excellent features and it has never been used to machine SiCp/Al composites. In order to improve the machinability and application of SiCp/Al composites, the rotary ultrasonic face grinding experiments of SiCp/Al composites reinforced with 45% volume SiC particles were carried out to investigate cutting force, surface quality, tool wear, and abrasive chip shapes. The experimental results indicate that ultrasonic vibration could reduce cutting force, surface roughness, surface defects, and increase plastic removal ratio. The cutting force could be lowered by an average of 13.86% and the surface roughness could be lowered by an average of 11.53%. The examined results of tool wear patterns suggest that tool wear is mainly caused by grain breakage and grain fall-off. Grinding wheel blockage and grinding burn were not observed in machining process.     

CFRP管面钻削缺陷形成机制

碳纤维增强复合材料(CFRP)传动轴因性能优越广泛应用于汽车、航空航天、船舶、冷却塔风机等轻量化领域,但其钻削过程中容易出现毛刺、分层等缺陷。为了揭示CFRP管面钻削缺陷形成机制,选择双锋角钻头和三尖二刃钻对CFRP管面钻孔,利用分步钻削盲孔和通孔的方法,分析了损伤部位的受力情况,揭示了入口撕裂、出口毛刺和分层产生原因。根据实验结果,发现双锋角钻头钻孔时入口撕裂损伤较大,损伤位置在钻头与管面接触最低点,且主要是那部分水平缠绕CFRP管的纤维,原因是水平缠绕的纤维屈曲变形最大,对切削力更加敏感。双锋角钻头和三尖二刃钻的横刃对孔最终出口分层没有影响,主切削刃的切削行为决定孔最终出口分层。相同钻头钻孔时,轴向力不是唯一影响分层因子的因素,还需考虑切削热。相比双锋角钻头,三尖二刃钻因锋利的外缘尖角能有效划断纤维,使出口分层较小。