Research Progress on Interference Fit Joint Technology in Carbon Fiber Composites
Citations
CAO Zengqiang, GUO Yingjiang, HUO Lubin. Research progress on interference fit joint technology in carbon fiber composites[J]. Aeronautical Manufacturing Technology, 2025, 68(18): 14–25.
图1 不同挤压量下的单板试件疲劳寿命增益系数[ 葛恩德. 碳纤维复合材料及其叠层连接结构孔挤压强化技术研究[D]. 南京: 南京航空航天大学, 2015.GE Ende. Research on hole expansion strengthing technology of composites and their stacks joint structures[D]. Nanjing: Nanjing University of Aeronautics and Astronautics, 2015. 35]
图2 CFRP构件3种铆接方式示意图[ 赵乐天, 杨天智, 黄祺, 等. CFRP构件垫圈/衬套铆接损伤及拉剪性能试验研究[J]. 西北工业大学学报, 2023, 41(6): 1089–1096.ZHAO Letian, YANG Tianzhi, HUANG Qi, et al. Damage behavior and mechanical property investigation of CFRP/CFRP washer-bushing riveted joints[J]. Journal of Northwestern Polytechnical University, 2023, 41(6): 1089–1096. 37]
图3 干涉螺栓插入过程力学阶段划分[ 邹鹏. 复合材料干涉螺接结构损伤萌生与扩展机理研究[D]. 西安: 西北工业大学, 2017.ZOU Peng. Research on the damage initiation and evolution mechanism of composite interference-fit bolted structures[D]. Xi’an: Northwestern Polytechnical University, 2017. 41]
图4 抽芯铆钉的铆接过程[ 王兵兵, 周钊元, 金万军, 等. CFRP/Al抽芯铆钉单剪干涉配合的渐进损伤数值模拟研究[J]. 复合材料学报, 2024, 41(6): 3258–3270.WANG Bingbing, ZHOU Zhaoyuan, JIN Wanjun, et al. Numerical simulation of progressive damage of single-lap CFRP/Al connected by blind rivet under interference condition[J]. Acta Materiae Compositae Sinica, 2024, 41(6): 3258–3270. 29]
图9 GromEx®干涉连接与间隙连接疲劳寿命对比[ REID L, RANSOM J, WEHRMEISTER M. Grommet hole reinforcement and lightning strike protection in composite structural assembly[J]. SAE International Journal of Aerospace, 2011, 4(2): 988–997. 42]
图10 不同铆接方法形成的干涉量[ CAO Z Q, CARDEW-HALL M. Interference-fit riveting technique in fiber composite laminates[J]. Aerospace Science and Technology, 2006, 10(4): 327–330. 12]
图11 动态和静态安装方式对应的第一层碳纤维复合材料的损伤系数[ ZUO Y J, CAO Z Q, ZHENG G, et al. Damage behavior investigation of CFRP/Ti bolted joint during interference fit bolt dynamic installation progress[J]. Engineering Failure Analysis, 2020, 111: 104454. 43]
图12 渐进损伤分析流程图[ 魏景超, 矫桂琼, 闫照明, 等. 单面螺纹抽钉干涉配合复合材料连接件挤压强度研究[J]. 航空学报, 2013, 34(7): 1627–1635.WEI Jingchao, JIAO Guiqiong, YAN Zhaoming, et al. Bearing strength of composite joints interference-fitted with blind bolts[J]. Acta Aeronautica et Astronautica Sinica, 2013, 34(7): 1627–1635. 39]
1.School of Mechanical Engineering, Northwestern Polytechnical University, Xi’an710072, China
2.NPU Xu Hang Electromagnetic Technology Co., Ltd., Xi’an710100, China
Citations
CAO Zengqiang, GUO Yingjiang, HUO Lubin. Research progress on interference fit joint technology in carbon fiber composites[J]. Aeronautical Manufacturing Technology, 2025, 68(18): 14–25.
Abstract
Carbon fiber reinforced polymer (CFRP) composites are widely used in aerospace applications owing to their high strength-to-weight ratio. Despite their advantages, mechanical fastening remains essential due to manufacturing limitations and structural load transfer requirements. Interference fit technology shows significant potential for enhancing the strength and fatigue life of mechanicaly fastened CFRP joints. However, the inherent brittleness and low interlaminar strength of CFRP materials pose significant challenges to its application. To address these issues, this paper reviews the research progress on interference fit connection technology for CFRP composite materials, both domestically and internationally. It analyzes the fatigue life enhancement mechanisms associated with interference fit connections, introduces the primary process methods used for achieving interference fits in CFRP composites, and discusses the key factors influencing interference fit connection quality. Based on this review, future development trends and application prospects of CFRP interference fit connection technologies are discussed.
碳纤维增强树脂基复合材料(Carbon fiber reinforced polymer,CFRP)是一种由碳纤维及树脂基体组合而成的材料[ HEGDE S, SATISH SHENOY B, CHETHAN K N. Review on carbon fiber reinforced polymer (CFRP) and their mechanical performance[J]. Materials Today: Proceedings, 2019, 19: 658–662. 1]。自20世纪60年代以来,伴随着对高强度轻质材料需求不断增加,CFRP逐步应用于航空航天、风力涡轮机及耐腐蚀压力容器等领域[ PERNER M, ALGERMISSEN S, KEIMER R, et al. Avoiding defects in manufacturing processes: A review for automated CFRP production[J]. Robotics and Computer-Integrated Manufacturing, 2016, 38: 82–92. 2]。尤其是在飞机上,CFRP广泛应用于水平和垂直安定面、襟翼、机翼蒙皮和各种控制面[ GIBSON R F. Principles of Composite Material Mechanics[M]. Boca Raton: CRC Press, 2007. 3]。采用复合材料结构的前机身段,可比金属结构减轻质量31.5%,减少零件数量61.5%,减少紧固件61.3%;复合材料垂直安定面可减轻质量32.24%[ 杨珍菊. 国外复合材料行业进展与应用(下)[J]. 纤维复合材料, 2017, 34(3): 36–39.YANG Zhenju. Progress and application of composite materials industry in foreign countries (II)[J]. Fiber Composites, 2017, 34(3): 36–39. 4]。空客公司推出的新一代超宽体客机A350XWB上的复合材料比重高达53%,机翼、尾翼、机身与整流罩等关键部位都采用了复合材料[ 段元欣. CFRP螺栓干涉连接结构预紧行为及静强度研究[D]. 西安: 西北工业大学, 2015.DUAN Yuanxin. The preloading behavior and strength of bolted CFRP laminate joints with interference-fit[D]. Xi’an: Northwestern Polytechnical University, 2015. 5]。
由于制造技术的限制和载荷传递的要求,复合材料结构的机械连接仍然无法避免[ ZUO Y J, CAO Z Q, CAO Y J, et al. Dynamic behavior of CFRP/Ti single-lap pinned joints under longitudinal electromagnetic dynamic loading[J]. Composite Structures, 2018, 184: 362–371. 曹增强, 张铭豪, 谭学才, 等. 航空复合材料结构铆接技术综述[J]. 航空制造技术, 2023, 63(1/2): 26–37.CAO Zengqiang, ZHANG Minghao, TAN Xuecai, et al. Overview of riveting technology for aviation composite structure[J]. Aeronautical Manufacturing Technology, 2023, 63(1/2): 26–37. 曹增强. 新机研制中的复合材料结构装配关键技术[J]. 航空制造技术, 2009, 52(15): 40–42.CAO Zengqiang. Key assembly technologies of composite structures in developing new aircraft[J]. Aeronautical Manufacturing Technology, 2009, 52(15): 40–42. 6-8]。铆接、螺接等机械连接仍是目前复合材料结构(特别是主承载结构)的主要连接方法。然而,连接所需的开孔破坏了复合材料纤维的连续性,会导致局部应力集中[ AHMAD J. Machining of polymer composites[M]. Boston: Springer, 2009. ABRÃO A M, FARIA P E, CAMPOS RUBIO J C, et al. Drilling of fiber reinforced plastics: A review[J]. Journal of Materials Processing Technology, 2007, 186(1–3): 1–7. PANCHAGNULA K K, PALANIYANDI K. Drilling on fiber reinforced polymer/nanopolymer composite laminates: A review[J]. Journal of Materials Research and Technology, 2018, 7(2): 180–189. 9-11]。复合材料开孔结构可引发疲劳裂纹萌生,60%~80%的结构失效发生在开孔接头处[ CAO Z Q, CARDEW-HALL M. Interference-fit riveting technique in fiber composite laminates[J]. Aerospace Science and Technology, 2006, 10(4): 327–330. WANG X H, CAO Z Q. A dynamic installation method to improve the morphological characteristics of the bolt-hole contact interface in CFRP interference bolted structures[J]. Engineering Failure Analysis, 2024, 156: 107818. 12-13]。因此通过合适的工艺提高复合材料开孔结构的强度,从而提高复合材料连接接头的强度和寿命十分必要。对于广泛使用的金属开孔结构,干涉(过盈)配合连接方法能够有效降低应力集中,提高连接结构的强度和疲劳寿命[ OFSTHUN M. When fatigue quality enhancers do not enhance fatigue quality[J]. International Journal of Fatigue, 2003, 25(9–11): 1223–1228. 程晖, 樊新田, 徐冠华, 等. 航空复合材料结构精密干涉连接技术综述[J]. 航空学报, 2021, 42(10): 524876.CHENG Hui, FAN Xintian, XU Guanhua, et al. State of the art of precise interference-fit technology for composite structures in aircraft[J]. Acta Aeronautica et Astronautica Sinica, 2021, 42(10): 524876. 14-15]。复合材料具有延伸率小、层间强度低、抗冲击性能差等特点,在使用压入法或锤击法形成干涉时将承受较大轴向力,会发生分层、脱胶等损伤,从而降低整体强度[ COLE R T, BATEH E J, POTTER J. Fasteners for composite structures[J]. Composites, 1982, 13(3): 233–240. 宋丹龙, 张开富, 钟衡, 等. 层合板干涉螺接分层损伤及其临界干涉量[J]. 航空学报, 2016, 37(5): 1677–1688.SONG Danlong, ZHANG Kaifu, ZHONG Heng, et al. Delamination damage and critical interference percentage for interference fit bolt joint of laminates[J]. Acta Aeronautica et Astronautica Sinica, 2016, 37(5): 1677–1688. 16-17]。起初,研究人员普遍认为干涉配合连接不适合复合材料结构。而在19世纪80年代,原麦道公司指出干涉配合连接可以提高碳环氧树脂复合材料的疲劳寿命[ BUNIN B L. Critical composite joint subcomponents: Analysis and test results: NASA-CR-3711[R]. NASA,1983. 18]。之后大量的研究也证明,在较低的干涉量和较高的侧向限制条件下,对于复合材料开孔结构使用干涉配合连接方法能够显著降低应力集中,提高连接结构的强度和疲劳寿命[ 曹增强, 佘公藩, 李志饶, 等. 复合材料的干涉配合铆接[J]. 航空制造工程, 1997(2): 8–9.CAO Zengqiang, SHE Gongfan, LI Zhirao, et al. Interference fit riveting of composite materials[J]. Aviation Maintenance & Engineering, 1997(2): 8–9. 刘风雷. 用于复合材料干涉结构的多功能紧固系统[J]. 航空制造技术, 2007, 50(3): 98–101.LIU Fenglei. Multifunctional fastening system for composite interference structures[J]. Aeronautical Manufacturing Technology, 2007, 50(3): 98–101. PRAMANIK A, BASAK A K, DONG Y, et al. Joining of carbon fibre reinforced polymer (CFRP) composites and aluminium alloys—A review[J]. Composites Part A: Applied Science and Manufacturing, 2017, 101: 1–29. 19-21]。
然而,针对复合材料结构的干涉配合连接仍存在一些问题。主要包括:不可拆卸不便于检查和维修[ FATIGUE TECHNOLOGY. ForceMate bushings[EB/OL]. [2024–03–29]. https://fatiguetech.com/products/forcemate-bushings. CHENG Y Q, SU H H, FU Y C, et al. Numerical simulation on stress distribution and failure of composites holes with cold expansion[J]. Materials Science Forum, 2013, 770: 221–225. 魏誉豪, 曹增强. 复合材料结构装配中的干涉衬套强化工艺研究[J]. 航空制造技术, 2019, 62(15): 63–67, 74.WEI Yuhao, CAO Zengqiang. Research on reinforcement of interference bushing in composite structure assembly[J]. Aeronautical Manufacturing Technology, 2019, 62(15): 63–67, 74. 22-24];最佳干涉量远小于金属,且缺乏推荐参数标准[ 曹增强, 王武, 杨军. 干涉对复合材料机械连接强度的影响[J]. 航空制造技术, 2012, 55(12): 62–64, 67.CAO Zengqiang, WANG Wu, YANG Jun. Effect of interference-fit on failure of composites bolted joint[J]. Aeronautical Manufacturing Technology, 2012, 55(12): 62–64, 67. CAO Y J, CAO Z Q, ZUO Y J, et al. Numerical and experimental investigation of fitting tolerance effects on damage and failure of CFRP/Ti double-lap single-bolt joints[J]. Aerospace Science and Technology, 2018, 78: 461–470. ZUO Y J, YUE T, JIANG R S, et al. Bolt insertion damage and mechanical behaviors investigation of CFRP/CFRP interference fit bolted joints[J]. Chinese Journal of Aeronautics, 2022, 35(9): 354–365. 25-27];过大的安装力会对孔壁及孔口造成损伤[ WANG X H, CAO Z Q, WANG Y, et al. Influence of bolt dynamic installation on topography characteristics and mechanical behaviors of CFRP interference-fit bolted joints[J]. Chinese Journal of Aeronautics, 2024, 37(2): 482–500. 王兵兵, 周钊元, 金万军, 等. CFRP/Al抽芯铆钉单剪干涉配合的渐进损伤数值模拟研究[J]. 复合材料学报, 2024, 41(6): 3258–3270.WANG Bingbing, ZHOU Zhaoyuan, JIN Wanjun, et al. Numerical simulation of progressive damage of single-lap CFRP/Al connected by blind rivet under interference condition[J]. Acta Materiae Compositae Sinica, 2024, 41(6): 3258–3270. WANG A Y, WANG Z Q, ZHAO M L, et al. Effects of ply thickness and interference-fit on the bearing strength of single-lap countersunk composite joints[J]. Thin-Walled Structures, 2023, 189: 110878. 28-30];干涉形成的轴向残余应力分布不均匀[ CAO Z Q, CARDEW-HALL M. Interference-fit riveting technique in fiber composite laminates[J]. Aerospace Science and Technology, 2006, 10(4): 327–330. 12, LISI AEROSPACE. Sleeve taper HI-LITETM system[EB/OL]. [2024–03–29]. http://lisi.aerospace.pelham.localhost/en/product/sleeve-taper-hi-lite-system/. 31]等。这些问题制约了干涉配合连接技术在CFRP中的广泛应用。目前,国外新机型研制中复材用量大幅度提高,波音787和空客A350的主承力结构使用了大量复合材料。为减小复合材料损伤,这些机型使用干涉配合连接技术装配时通常使用LISI、PCC等公司的连接件进行干涉配合连接[ 刘华东, 赵庆云. 长寿命机械连接技术研究应用进展[J]. 航空制造技术, 2016, 59(19): 64–69, 79.LIU Huadong, ZHAO Qingyun. Development of long-life mechanical joining technology[J]. Aeronautical Manufacturing Technology, 2016, 59(19): 64–69, 79. 32]。中国自主研制的C909和C919在非承力结构中使用了复合材料,其结构主要采用无头铆钉、单面螺纹抽芯铆钉等紧固件进行小干涉连接(0.05%~0.35%)[ 高星海, 曹增强. 钛合金干涉配合高锁螺栓应力波安装质量分析[J]. 机械科学与技术, 2012, 31(1): 138–140, 145.GAO Xinghai, CAO Zengqiang. Quality analysis of the interference-fit hi-lock bolts manufactured by titanium alloy using stress wave[J]. Mechanical Science and Technology for Aerospace Engineering, 2012, 31(1): 138–140, 145. 33]。
(1)应力集中的影响。应力集中是影响结构疲劳强度最重要的因素之一。由于结构形状、机械加工、材料组成与内部组织等原因,应力集中是一个普遍现象。复合材料由两种或两种以上性质不同的材料组成,由于具有各向异性、非线性等力学特点,其强度理论的研究面临较大困难。为了研究应力集中对复合材料结构疲劳寿命的影响,理论研究中普遍采用Zweben模型,也即修正的剪滞模型。根据该模型,树脂基复合材料在单向拉伸时,其破坏往往始于某些带缺陷的弱纤维,当一根或数根弱纤维断裂形成裂纹后,在其周围便会产生局部应力扰动,邻近纤维与基体受此扰动将产生细观应力集中[ 曹增强, 张岐良. 飞机结构干涉配合强化理论及应用[M]. 北京: 国防工业出版社, 2016.CAO Zengqiang, ZHANG Qiliang. Fatigue enhancing theory of interference fit and its application in aircraft structures[M]. Beijing: National Defense Industry Press, 2016. 34]。
(2)残余应力的影响。干涉配合在复合材料孔壁引入预压应力,与未干涉情况相比降低了在外部循环载荷下的平均应力,延缓疲劳裂纹萌生。预压应力以拉应力的形式存在,当结构处于拉伸外载作用时,该预压应力与外载在孔边引起的应力相互叠加,从而改变了孔边的应力分布,使孔边危险区的应力幅值比无干涉情况有所减小,延缓了接头配合部裂纹产生与扩展,因而大幅度提高结构的疲劳强度[ 程晖, 樊新田, 徐冠华, 等. 航空复合材料结构精密干涉连接技术综述[J]. 航空学报, 2021, 42(10): 524876.CHENG Hui, FAN Xintian, XU Guanhua, et al. State of the art of precise interference-fit technology for composite structures in aircraft[J]. Acta Aeronautica et Astronautica Sinica, 2021, 42(10): 524876. 15]。
(3)传载有效接触面积的影响。干涉量对层合板最小截面传载幅值及危险部位应力幅值,与有效接触面积存在一定的关系。葛恩德[ 葛恩德. 碳纤维复合材料及其叠层连接结构孔挤压强化技术研究[D]. 南京: 南京航空航天大学, 2015.GE Ende. Research on hole expansion strengthing technology of composites and their stacks joint structures[D]. Nanjing: Nanjing University of Aeronautics and Astronautics, 2015. 35]在对复合材料层合板孔金属无缝衬套孔挤压试验与仿真研究中发现,在较高的循环载荷加载条件下,无论干涉量大小如何,疲劳增益系数都为负值,即干涉衬套未对复合材料带孔试件疲劳寿命起到提高作用,如图1所示。
图1 不同挤压量下的单板试件疲劳寿命增益系数[ 葛恩德. 碳纤维复合材料及其叠层连接结构孔挤压强化技术研究[D]. 南京: 南京航空航天大学, 2015.GE Ende. Research on hole expansion strengthing technology of composites and their stacks joint structures[D]. Nanjing: Nanjing University of Aeronautics and Astronautics, 2015. 35]
Fig.1 Fatigue life gain coefficient of single plate specimens under differentextrusion amounts[ 葛恩德. 碳纤维复合材料及其叠层连接结构孔挤压强化技术研究[D]. 南京: 南京航空航天大学, 2015.GE Ende. Research on hole expansion strengthing technology of composites and their stacks joint structures[D]. Nanjing: Nanjing University of Aeronautics and Astronautics, 2015. 35]
Zhang等[ ZHANG Q L, CAO Z Q, WEI F Y, et al. Mechanical analysis of a pin interference-fitted sheet under tensile loading[J]. Journal of Aerospace Engineering, 2016, 29(4): 04015085. 36]在对干涉配合销轴对孔疲劳寿命增强机制的研究中也发现了上述现象。研究发现固有的载荷传递机械特性是干涉配合接头的主要疲劳增强机制。连接构件的弹性变形及紧固件与孔之间的接触对于减小旁路载荷范围起着至关重要的作用。应力分析表明如果加载过程中不发生分离,干涉配合接头孔边缘处的交变应力与间隙配合或紧配合接头相比降低了50%以上;但是过载可能会使接头由过盈配合转为间隙配合,从而减少接触面积,降低旁路载荷范围内的自动调节能力,显然这对疲劳性能是不利的。这些规律可以体现出以下机理:在复合材料干涉配合结构中,干涉量对层合板传载幅值及危险点的应力幅值的影响,是与紧固孔与紧固件之间的接触有必然联系的;正是钉孔接触对结构各组件弹性变形的调节作用,改变了复合材料结构内部载荷(传载、应力)的幅值。干涉配合增加了紧固件与连接孔的有效接触面积,干涉配合下孔与紧固件之间的摩擦力将阻止孔边内壁变形的扩张,能够有效抑制裂纹扩展[ 曹增强, 张岐良. 飞机结构干涉配合强化理论及应用[M]. 北京: 国防工业出版社, 2016.CAO Zengqiang, ZHANG Qiliang. Fatigue enhancing theory of interference fit and its application in aircraft structures[M]. Beijing: National Defense Industry Press, 2016. 34]。
干涉配合连接的优势主要体现在其疲劳强化能力上。将之应用于传统金属材料,已经展现出巨大的工程潜力和良好的增益效果。但由于疲劳寿命增益机理的不同,将干涉配合连接技术应用到CFRP结构仍面临一些问题,为此研究者们提出了许多新的工艺方法。以干涉实现方式为依据区分,CFRP连接结构的干涉配合连接工艺方法主要有径向扩张法[ CAO Z Q, CARDEW-HALL M. Interference-fit riveting technique in fiber composite laminates[J]. Aerospace Science and Technology, 2006, 10(4): 327–330. 12, 赵乐天, 杨天智, 黄祺, 等. CFRP构件垫圈/衬套铆接损伤及拉剪性能试验研究[J]. 西北工业大学学报, 2023, 41(6): 1089–1096.ZHAO Letian, YANG Tianzhi, HUANG Qi, et al. Damage behavior and mechanical property investigation of CFRP/CFRP washer-bushing riveted joints[J]. Journal of Northwestern Polytechnical University, 2023, 41(6): 1089–1096. 37]、直接压入法[ ZUO Y J, YUE T, JIANG R S, et al. Bolt insertion damage and mechanical behaviors investigation of CFRP/CFRP interference fit bolted joints[J]. Chinese Journal of Aeronautics, 2022, 35(9): 354–365. 27, 张俊琪, 刘龙权, 陈昆昆, 等. 干涉配合对复合材料机械连接结构承载能力的影响[J]. 上海交通大学学报, 2013, 47(11): 1795–1800, 1806.ZHANG Junqi, LIU Longquan, CHEN Kunkun, et al. Influence of bolt-hole interference fit conditions on load capacity in composite mechanical joints[J]. Journal of Shanghai Jiao Tong University, 2013, 47(11): 1795–1800, 1806. 38]和间接压入法[ 葛恩德. 碳纤维复合材料及其叠层连接结构孔挤压强化技术研究[D]. 南京: 南京航空航天大学, 2015.GE Ende. Research on hole expansion strengthing technology of composites and their stacks joint structures[D]. Nanjing: Nanjing University of Aeronautics and Astronautics, 2015. 35, 魏景超, 矫桂琼, 闫照明, 等. 单面螺纹抽钉干涉配合复合材料连接件挤压强度研究[J]. 航空学报, 2013, 34(7): 1627–1635.WEI Jingchao, JIAO Guiqiong, YAN Zhaoming, et al. Bearing strength of composite joints interference-fitted with blind bolts[J]. Acta Aeronautica et Astronautica Sinica, 2013, 34(7): 1627–1635. 邹鹏, 屈凡. 复合材料衬套螺栓干涉连接安装过程损伤机制[J]. 复合材料学报, 2022, 39(5): 2449–2459.ZOU Peng, QU Fan. Damage mechanism of composite sleeve-type bolt interference fit structure during the installation process[J]. Acta Materiae Compositae Sinica, 2022, 39(5): 2449–2459. 39-40]等。
2.1 径向扩张法
径向扩张法是将预先放置在孔内的芯轴轴向压缩,使之径向扩张实现干涉的。通常使用铆钉作为干涉连接件。压铆、锤铆、气铆等传统方法使得铆钉膨胀不均匀,容易对复合材料孔壁造成损伤,难以实现高质量干涉配合。赵乐天等[ 赵乐天, 杨天智, 黄祺, 等. CFRP构件垫圈/衬套铆接损伤及拉剪性能试验研究[J]. 西北工业大学学报, 2023, 41(6): 1089–1096.ZHAO Letian, YANG Tianzhi, HUANG Qi, et al. Damage behavior and mechanical property investigation of CFRP/CFRP washer-bushing riveted joints[J]. Journal of Northwestern Polytechnical University, 2023, 41(6): 1089–1096. 37]使用压铆方法进行研究,对比了净铆接、衬套铆接、衬套/垫圈结合的铆接3种方法单搭接构件拉伸剪切性能及拉托性能的影响,3种铆接过程如图2所示;结果表明,结合金属衬套与垫圈对CFRP进行铆接有效限制了镦头附近的顶杆膨胀不均匀,与净铆接和衬套铆接相比,复合材料孔镦头侧损伤大幅度减少。
图2 CFRP构件3种铆接方式示意图[ 赵乐天, 杨天智, 黄祺, 等. CFRP构件垫圈/衬套铆接损伤及拉剪性能试验研究[J]. 西北工业大学学报, 2023, 41(6): 1089–1096.ZHAO Letian, YANG Tianzhi, HUANG Qi, et al. Damage behavior and mechanical property investigation of CFRP/CFRP washer-bushing riveted joints[J]. Journal of Northwestern Polytechnical University, 2023, 41(6): 1089–1096. 37]
Fig.2 Schematic diagram of three riveting methods for CFRP components[ 赵乐天, 杨天智, 黄祺, 等. CFRP构件垫圈/衬套铆接损伤及拉剪性能试验研究[J]. 西北工业大学学报, 2023, 41(6): 1089–1096.ZHAO Letian, YANG Tianzhi, HUANG Qi, et al. Damage behavior and mechanical property investigation of CFRP/CFRP washer-bushing riveted joints[J]. Journal of Northwestern Polytechnical University, 2023, 41(6): 1089–1096. 37]
2.2 直接压入法
直接压入法是指将直径大于孔的芯轴通过单侧压入的方法安装到复合材料孔中,且运动的芯轴直接与复合材料孔接触。该方法应用较广泛的是干涉螺栓连接件。邹鹏[ 邹鹏. 复合材料干涉螺接结构损伤萌生与扩展机理研究[D]. 西安: 西北工业大学, 2017.ZOU Peng. Research on the damage initiation and evolution mechanism of composite interference-fit bolted structures[D]. Xi’an: Northwestern Polytechnical University, 2017. 41]在其CFRP干涉螺栓安装过程损伤机理研究中介绍了干涉螺栓的安装过程,如图3所示;在干涉螺栓的压入过程中,钉孔之间的主要作用力体现为轴向摩擦力和径向挤压力;在这些作用力的影响下,复合材料会发生基体开裂、界面脱粘及分层等损伤。尤其是干涉量较大时,安装过程造成的损伤反而会降低结构的疲劳寿命。
图3 干涉螺栓插入过程力学阶段划分[ 邹鹏. 复合材料干涉螺接结构损伤萌生与扩展机理研究[D]. 西安: 西北工业大学, 2017.ZOU Peng. Research on the damage initiation and evolution mechanism of composite interference-fit bolted structures[D]. Xi’an: Northwestern Polytechnical University, 2017. 41]
Fig.3 Mechanical stages of the interference bolt insertion process[ 邹鹏. 复合材料干涉螺接结构损伤萌生与扩展机理研究[D]. 西安: 西北工业大学, 2017.ZOU Peng. Research on the damage initiation and evolution mechanism of composite interference-fit bolted structures[D]. Xi’an: Northwestern Polytechnical University, 2017. 41]
Zuo等[ ZUO Y J, YUE T, JIANG R S, et al. Bolt insertion damage and mechanical behaviors investigation of CFRP/CFRP interference fit bolted joints[J]. Chinese Journal of Aeronautics, 2022, 35(9): 354–365. 27]研究了CFRP/CFRP干涉配合连接的螺栓插入损伤及力学行为;试验结果表明干涉配合螺栓在孔入口处存在损伤,干涉量越大损伤越严重,但损伤对接头疲劳失效的影响不明显;此外,随着干涉量增大,接头的失效模式由螺栓头失效变为螺栓杆失效,即过盈配合可以使螺栓承受更严重的局部疲劳载荷,从而提高层合板孔的抗疲劳能力。
Fig.8 Flow chart of GromEx® installation on composite materials[ FATIGUE TECHNOLOGY. ForceMate bushings[EB/OL]. [2024–03–29]. https://fatiguetech.com/products/forcemate-bushings. 22]
图9 GromEx®干涉连接与间隙连接疲劳寿命对比[ REID L, RANSOM J, WEHRMEISTER M. Grommet hole reinforcement and lightning strike protection in composite structural assembly[J]. SAE International Journal of Aerospace, 2011, 4(2): 988–997. 42]
Fig.9 Comparison of fatigue life between GromEx® interference connection and gap connection[ REID L, RANSOM J, WEHRMEISTER M. Grommet hole reinforcement and lightning strike protection in composite structural assembly[J]. SAE International Journal of Aerospace, 2011, 4(2): 988–997. 42]
为了更直观地展示本文所介绍的相关研究,依据干涉工艺方法(径向扩张法、直接压入法、间接压入法)、干涉安装速率(动态、静态)、被连接材料与紧固件类型进行归纳和分类,见表1[ CAO Z Q, CARDEW-HALL M. Interference-fit riveting technique in fiber composite laminates[J]. Aerospace Science and Technology, 2006, 10(4): 327–330. WANG X H, CAO Z Q. A dynamic installation method to improve the morphological characteristics of the bolt-hole contact interface in CFRP interference bolted structures[J]. Engineering Failure Analysis, 2024, 156: 107818. 12-13, FATIGUE TECHNOLOGY. ForceMate bushings[EB/OL]. [2024–03–29]. https://fatiguetech.com/products/forcemate-bushings. 22, 魏誉豪, 曹增强. 复合材料结构装配中的干涉衬套强化工艺研究[J]. 航空制造技术, 2019, 62(15): 63–67, 74.WEI Yuhao, CAO Zengqiang. Research on reinforcement of interference bushing in composite structure assembly[J]. Aeronautical Manufacturing Technology, 2019, 62(15): 63–67, 74. 24, ZUO Y J, YUE T, JIANG R S, et al. Bolt insertion damage and mechanical behaviors investigation of CFRP/CFRP interference fit bolted joints[J]. Chinese Journal of Aeronautics, 2022, 35(9): 354–365. WANG X H, CAO Z Q, WANG Y, et al. Influence of bolt dynamic installation on topography characteristics and mechanical behaviors of CFRP interference-fit bolted joints[J]. Chinese Journal of Aeronautics, 2024, 37(2): 482–500. 王兵兵, 周钊元, 金万军, 等. CFRP/Al抽芯铆钉单剪干涉配合的渐进损伤数值模拟研究[J]. 复合材料学报, 2024, 41(6): 3258–3270.WANG Bingbing, ZHOU Zhaoyuan, JIN Wanjun, et al. Numerical simulation of progressive damage of single-lap CFRP/Al connected by blind rivet under interference condition[J]. Acta Materiae Compositae Sinica, 2024, 41(6): 3258–3270. WANG A Y, WANG Z Q, ZHAO M L, et al. Effects of ply thickness and interference-fit on the bearing strength of single-lap countersunk composite joints[J]. Thin-Walled Structures, 2023, 189: 110878. LISI AEROSPACE. Sleeve taper HI-LITETM system[EB/OL]. [2024–03–29]. http://lisi.aerospace.pelham.localhost/en/product/sleeve-taper-hi-lite-system/. 27-31, 葛恩德. 碳纤维复合材料及其叠层连接结构孔挤压强化技术研究[D]. 南京: 南京航空航天大学, 2015.GE Ende. Research on hole expansion strengthing technology of composites and their stacks joint structures[D]. Nanjing: Nanjing University of Aeronautics and Astronautics, 2015. 35, 赵乐天, 杨天智, 黄祺, 等. CFRP构件垫圈/衬套铆接损伤及拉剪性能试验研究[J]. 西北工业大学学报, 2023, 41(6): 1089–1096.ZHAO Letian, YANG Tianzhi, HUANG Qi, et al. Damage behavior and mechanical property investigation of CFRP/CFRP washer-bushing riveted joints[J]. Journal of Northwestern Polytechnical University, 2023, 41(6): 1089–1096. 37, 魏景超, 矫桂琼, 闫照明, 等. 单面螺纹抽钉干涉配合复合材料连接件挤压强度研究[J]. 航空学报, 2013, 34(7): 1627–1635.WEI Jingchao, JIAO Guiqiong, YAN Zhaoming, et al. Bearing strength of composite joints interference-fitted with blind bolts[J]. Acta Aeronautica et Astronautica Sinica, 2013, 34(7): 1627–1635. 邹鹏, 屈凡. 复合材料衬套螺栓干涉连接安装过程损伤机制[J]. 复合材料学报, 2022, 39(5): 2449–2459.ZOU Peng, QU Fan. Damage mechanism of composite sleeve-type bolt interference fit structure during the installation process[J]. Acta Materiae Compositae Sinica, 2022, 39(5): 2449–2459. 邹鹏. 复合材料干涉螺接结构损伤萌生与扩展机理研究[D]. 西安: 西北工业大学, 2017.ZOU Peng. Research on the damage initiation and evolution mechanism of composite interference-fit bolted structures[D]. Xi’an: Northwestern Polytechnical University, 2017. REID L, RANSOM J, WEHRMEISTER M. Grommet hole reinforcement and lightning strike protection in composite structural assembly[J]. SAE International Journal of Aerospace, 2011, 4(2): 988–997. ZUO Y J, CAO Z Q, ZHENG G, et al. Damage behavior investigation of CFRP/Ti bolted joint during interference fit bolt dynamic installation progress[J]. Engineering Failure Analysis, 2020, 111: 104454. 39-43]。
表1 关于CFRP干涉配合连接的研究现状汇总
Table 1 Summary of research status on interference fit connection of CFRP
干涉工艺方法
安装速率
被连接材料
紧固件
文献来源
径向扩张法
动态
CFRP
铆钉
[ CAO Z Q, CARDEW-HALL M. Interference-fit riveting technique in fiber composite laminates[J]. Aerospace Science and Technology, 2006, 10(4): 327–330. 12]
静态
CFRP
铆钉
[ 葛恩德. 碳纤维复合材料及其叠层连接结构孔挤压强化技术研究[D]. 南京: 南京航空航天大学, 2015.GE Ende. Research on hole expansion strengthing technology of composites and their stacks joint structures[D]. Nanjing: Nanjing University of Aeronautics and Astronautics, 2015. 35]
直接压入法
动态
CFRP或金属
干涉螺栓
[ WANG X H, CAO Z Q. A dynamic installation method to improve the morphological characteristics of the bolt-hole contact interface in CFRP interference bolted structures[J]. Engineering Failure Analysis, 2024, 156: 107818. 13]
静态
CFRP
干涉螺栓
[ ZUO Y J, YUE T, JIANG R S, et al. Bolt insertion damage and mechanical behaviors investigation of CFRP/CFRP interference fit bolted joints[J]. Chinese Journal of Aeronautics, 2022, 35(9): 354–365. 27]
动态
CFRP
干涉螺栓
[ WANG X H, CAO Z Q, WANG Y, et al. Influence of bolt dynamic installation on topography characteristics and mechanical behaviors of CFRP interference-fit bolted joints[J]. Chinese Journal of Aeronautics, 2024, 37(2): 482–500. 28]
静态
CFRP
干涉螺栓
[ WANG A Y, WANG Z Q, ZHAO M L, et al. Effects of ply thickness and interference-fit on the bearing strength of single-lap countersunk composite joints[J]. Thin-Walled Structures, 2023, 189: 110878. 30]
[ 赵乐天, 杨天智, 黄祺, 等. CFRP构件垫圈/衬套铆接损伤及拉剪性能试验研究[J]. 西北工业大学学报, 2023, 41(6): 1089–1096.ZHAO Letian, YANG Tianzhi, HUANG Qi, et al. Damage behavior and mechanical property investigation of CFRP/CFRP washer-bushing riveted joints[J]. Journal of Northwestern Polytechnical University, 2023, 41(6): 1089–1096. 37]
静态
CFRP
衬套螺栓
[ 魏景超, 矫桂琼, 闫照明, 等. 单面螺纹抽钉干涉配合复合材料连接件挤压强度研究[J]. 航空学报, 2013, 34(7): 1627–1635.WEI Jingchao, JIAO Guiqiong, YAN Zhaoming, et al. Bearing strength of composite joints interference-fitted with blind bolts[J]. Acta Aeronautica et Astronautica Sinica, 2013, 34(7): 1627–1635. 39]
动态
CFRP
干涉衬套
[ 邹鹏, 屈凡. 复合材料衬套螺栓干涉连接安装过程损伤机制[J]. 复合材料学报, 2022, 39(5): 2449–2459.ZOU Peng, QU Fan. Damage mechanism of composite sleeve-type bolt interference fit structure during the installation process[J]. Acta Materiae Compositae Sinica, 2022, 39(5): 2449–2459. 40]
静态
CFRP
干涉螺栓
[ 邹鹏. 复合材料干涉螺接结构损伤萌生与扩展机理研究[D]. 西安: 西北工业大学, 2017.ZOU Peng. Research on the damage initiation and evolution mechanism of composite interference-fit bolted structures[D]. Xi’an: Northwestern Polytechnical University, 2017. 41]
动态
CFRP
干涉衬套
[ REID L, RANSOM J, WEHRMEISTER M. Grommet hole reinforcement and lightning strike protection in composite structural assembly[J]. SAE International Journal of Aerospace, 2011, 4(2): 988–997. 42]
静态
CFRP与Ti
干涉螺栓
[ ZUO Y J, CAO Z Q, ZHENG G, et al. Damage behavior investigation of CFRP/Ti bolted joint during interference fit bolt dynamic installation progress[J]. Engineering Failure Analysis, 2020, 111: 104454. 43]
大量研究表明,对于干涉配合连接问题,干涉量与干涉均匀性是影响结构强度与寿命的两个重要指标。与金属相比,复合材料层内和层间强度低,过大干涉量造成的损伤会降低接头的强度与疲劳寿命。复合材料结构连接面临“干涉破坏强度,非干涉降低性能”这一矛盾。同时沿轴向干涉的不均匀会导致残余应力的分布不均匀,造成加载过程中出现严重的应力集中,进而造成孔周损伤[ 程晖, 樊新田, 徐冠华, 等. 航空复合材料结构精密干涉连接技术综述[J]. 航空学报, 2021, 42(10): 524876.CHENG Hui, FAN Xintian, XU Guanhua, et al. State of the art of precise interference-fit technology for composite structures in aircraft[J]. Acta Aeronautica et Astronautica Sinica, 2021, 42(10): 524876. 15]。针对干涉配合连接的干涉量与干涉均匀性已有较多讨论。
针对干涉配合铆接的干涉均匀性问题。Cao等[ CAO Z Q, CARDEW-HALL M. Interference-fit riveting technique in fiber composite laminates[J]. Aerospace Science and Technology, 2006, 10(4): 327–330. 12]使用电磁铆接(Electromagnetic riveting,EMR)技术以较快的成形速度完成铆接,在复合材料孔中产生了较为理想的过盈配合;如图10所示,铆接造成的钉杆部分的干涉量对比,压铆为2.3%,而电磁铆接为0.8%。与压铆相比电磁铆接方法提高了钉杆径向变形的均匀性。即便如此,干涉均匀性仍不可忽略,干涉不均匀会影响复合材料干涉配合连接的强化效果。
图10 不同铆接方法形成的干涉量[ CAO Z Q, CARDEW-HALL M. Interference-fit riveting technique in fiber composite laminates[J]. Aerospace Science and Technology, 2006, 10(4): 327–330. 12]
Fig.10 Interference caused by different riveting methods[ CAO Z Q, CARDEW-HALL M. Interference-fit riveting technique in fiber composite laminates[J]. Aerospace Science and Technology, 2006, 10(4): 327–330. 12]
Wang等[ WANG X H, CAO Z Q, WANG Y, et al. Influence of bolt dynamic installation on topography characteristics and mechanical behaviors of CFRP interference-fit bolted joints[J]. Chinese Journal of Aeronautics, 2024, 37(2): 482–500. 28]针对CFRP干涉螺栓的干涉量与干涉均匀性问题,提出了一种动态安装方法;与传统的静态安装方法相比,所提出的动态方法以较高的速度(3~6 m/s)进行干涉螺栓的安装;通过动静态安装方法试验与有限元分析对比得出:动态方法显著降低了安装阻力,其接头在孔出入口处的干涉量差别小(即实现了更均匀的干涉),复合材料孔周应力分布均匀性优于静态方法;该研究提出了一种全新的安装工艺方法并对之进行了原理分析,但没有对加载速率这一关键因素进行定量分析,无法揭示动态方法优越性的真正机理。
邹鹏等[ 邹鹏, 屈凡. 复合材料衬套螺栓干涉连接安装过程损伤机制[J]. 复合材料学报, 2022, 39(5): 2449–2459.ZOU Peng, QU Fan. Damage mechanism of composite sleeve-type bolt interference fit structure during the installation process[J]. Acta Materiae Compositae Sinica, 2022, 39(5): 2449–2459. 40]针对复合材料衬套螺栓干涉连接安装过程开展了试验和有限元研究,分析了安装过程中的插钉力变化、形貌及孔壁损伤,并且以孔壁不分层为目标获得了临界干涉量;试验和模拟结果得出干涉量在2.4%以内可以保证较好的承载性能,高于先前航空工业推荐的干涉量范围0.4%~1.7%;然而研究者强调此结论只针对该研究的模型尺寸和材料。在对CFRP层合板进行层内渐进损伤模拟时,使用的是改进的三维Hashin准则[ CHANG F K, CHANG K Y. Post-failure analysis of bolted composite joints in tension or shear-out mode failure[J]. Journal of Composite Materials, 1987, 21(9): 809–833. CAMANHO P P, MATTHEWS F L. A progressive damage model for mechanically fastened joints in composite laminates[J]. Journal of Composite Materials, 1999, 33(24): 2248–2280. 44-45],这是因为Hashin准则[ TSERPES K I, LABEAS G, PAPANIKOS P, et al. Strength prediction of bolted joints in graphite/epoxy composite laminates[J]. Composites Part B: Engineering, 2002, 33(7): 521–529. 46]在纤维拉伸失效判据中包含的剪切项会对损伤过度估计,结果相对保守。该研究使用最大应力准则代替了Hashin准则中的纤维拉伸失效判据,因此得到较大临界干涉量。虽然在该研究中有限元分析结果与试验结果误差在允许范围内,但其推荐干涉量仍无法广泛推广。
魏誉豪等[ 魏誉豪, 曹增强. 复合材料结构装配中的干涉衬套强化工艺研究[J]. 航空制造技术, 2019, 62(15): 63–67, 74.WEI Yuhao, CAO Zengqiang. Research on reinforcement of interference bushing in composite structure assembly[J]. Aeronautical Manufacturing Technology, 2019, 62(15): 63–67, 74. 24]研究了干涉量对安装TA2纯钛衬套的复合材料损伤情况,设计了1%~5%的5组干涉量,在使用压铆机进行静态安装后主要针对安装阻力、孔径变化和内部损伤进行了讨论;通过研究发现,安装阻力随着干涉量的增大明显增加;安装后的孔径沿安装方向有较大区别,即干涉不均匀,因此建议将衬套设计为锥形孔;对内部损伤的观察发现,干涉量>3%时,复合材料损伤严重且衬套在出口处形成超过0.45 mm的凸瘤,建议干涉量选取不宜超过3%。此研究针对干涉量这一变量进行了试验,干涉量的选取范围很大,超越了先前的研究。但遗憾的是,此研究仅对安装阻力、干涉均匀性、损伤情况进行了定性描述,没有对干涉后结构的强度或寿命进行进一步研究,所以提出的临界干涉量缺乏说服力。
针对复合材料干涉螺栓安装损伤及力学行为问题,Zuo等[ ZUO Y J, YUE T, JIANG R S, et al. Bolt insertion damage and mechanical behaviors investigation of CFRP/CFRP interference fit bolted joints[J]. Chinese Journal of Aeronautics, 2022, 35(9): 354–365. 27]开展了系统的试验研究,不仅考虑了过盈配合情况,还增加了间隙配合情况作为对比,其研究的干涉量范围为–0.1%~1.61%;针对干涉安装接头分别进行了准静态和循环载荷加载,并使用扫描电子显微镜和高分辨率X射线微型扫描检查了层合板中的微观损伤。经过分析,该研究得出以下重要结论:(1)随着干涉量增大,上层板与靠近孔壁的层合板边界损伤越大;(2)虽然大的干涉量造成更大的损伤,但对干涉配合接头的失效位移与失效载荷影响较小;(3)适当的干涉量能提高接头疲劳寿命,但不同循环载荷水平下的临界干涉量不同,而且螺栓的插入损伤对接头疲劳失效影响不明显;该研究还表明:复合材料干涉配合对连接结构的静载承载能力影响不大,所以当分析干涉量影响时可以不过分关注对静载强度的增益效果;针对不同大小的循环载荷工况,复合材料干涉配合连接的临界干涉量也不同,这指向一个所需关注的要点,即要考虑载荷情况对疲劳寿命增益效果的影响。
在针对CFRP/Al抽芯铆钉单剪干涉配合的渐进损伤数值模拟研究中,王兵兵等[ 王兵兵, 周钊元, 金万军, 等. CFRP/Al抽芯铆钉单剪干涉配合的渐进损伤数值模拟研究[J]. 复合材料学报, 2024, 41(6): 3258–3270.WANG Bingbing, ZHOU Zhaoyuan, JIN Wanjun, et al. Numerical simulation of progressive damage of single-lap CFRP/Al connected by blind rivet under interference condition[J]. Acta Materiae Compositae Sinica, 2024, 41(6): 3258–3270. 29]基于连续损伤力学、扩展的三维破坏准则和应变率效应,通过对Abaqus二次开发建立了抽芯铆钉干涉配合模型,重点研究了安装速度对复合材料的损伤影响;有限元模型的分析结果发现,抽芯铆钉的安装阻力随着安装速度的增加而减小,同时损伤也随安装速度的增加而减少;相比于低干涉量,在高干涉量下速度对平均安装阻力所形成影响的差异较大。考虑安装速率对安装损伤的影响为进一步研究提供了启发。
Zuo等[ ZUO Y J, CAO Z Q, ZHENG G, et al. Damage behavior investigation of CFRP/Ti bolted joint during interference fit bolt dynamic installation progress[J]. Engineering Failure Analysis, 2020, 111: 104454. 43]针对CFRP/Ti干涉螺栓接头使用电磁动态安装方法进行试验研究,并与静态安装方法进行对比,评估了安装阻力及损伤机制。该研究得出以下重要结论:动态安装方法能降低中、大干涉量时的峰值安装力和剪切阻力;安装损伤主要发生在CFRP的孔入口与出口处;与静态方法相比,动态方法减少了首层的损伤,损伤系数降低0.9%~3.5%,且对干涉量大的情况损伤降低更明显,如图11所示。从该试验研究可见,在较大干涉量的干涉配合连接安装情况下动态方法的损伤小于静态方法的,在减轻损伤和增加临界干涉量方面有巨大潜力。
图11 动态和静态安装方式对应的第一层碳纤维复合材料的损伤系数[ ZUO Y J, CAO Z Q, ZHENG G, et al. Damage behavior investigation of CFRP/Ti bolted joint during interference fit bolt dynamic installation progress[J]. Engineering Failure Analysis, 2020, 111: 104454. 43]
Fig.11 Damage coefficient of the first layer of carbon fiber composite materialcorresponding to dynamic and static installation methods[ ZUO Y J, CAO Z Q, ZHENG G, et al. Damage behavior investigation of CFRP/Ti bolted joint during interference fit bolt dynamic installation progress[J]. Engineering Failure Analysis, 2020, 111: 104454. 43]
Wang等[ WANG X H, CAO Z Q, WANG Y, et al. Influence of bolt dynamic installation on topography characteristics and mechanical behaviors of CFRP interference-fit bolted joints[J]. Chinese Journal of Aeronautics, 2024, 37(2): 482–500. 28]使用动态安装方法针对CFRP接头进行干涉螺栓安装,研究了安装后的接头形貌特征和力学行为;在0~2.0%干涉量范围,通过试验获得了安装阻力及外部载荷下的机械性能,并以有限元模型模拟安装后应力分布和损伤行为。与先前研究类似,该研究发现与静态方法相比动态方法干涉阻力更小,且随着干涉量增大,安装阻力的下降比例也增大;同时,有限元分析结果表明动态方法产生的初始损伤较小。比较新颖的是,该研究还发现与静态安装方法相比,动态安装方法在连接件中引起的拉应力幅值更大且分布更广泛;该研究还对安装完成的连接接头进行了静态承载能力和疲劳寿命测试,发现动态安装方法使连接接头的最佳极限强度提升17.52%,刚度提高75.5%,疲劳寿命也有所增加。该研究建立了动态方法下损伤减少与强度增加的联系,这为后续研究提供了事实依据。
除了对安装工艺过程进行改进,也有研究者针对CFRP本身参数进行研究,寻找更加适合干涉配合连接的铺层结构。Wang等[ WANG A Y, WANG Z Q, ZHAO M L, et al. Effects of ply thickness and interference-fit on the bearing strength of single-lap countersunk composite joints[J]. Thin-Walled Structures, 2023, 189: 110878. 30]为了减轻复合材料干涉配合连接结构的损伤,研究了复合材料铺层厚度、铺层顺序和干涉尺寸对干涉螺栓安装损伤和连接接头强度的影响;通过准静态拉伸试验并结合扫描显微电镜进行断口分析,得到以下重要结论:薄层复合材料接头安装力要低于厚层复合材料的安装力;对失效的目视观察和SEM结果表明,薄层复合材料在干涉配合安装过程中的抗损伤能力更强。该研究的核心是从铺层厚度和纤维方向寻找更适合干涉配合连接的复合材料结构,但同时给出一个重要观点:干涉配合安装力的减小反映出损伤的减小,而安装损伤的大小直接影响干涉配合连接强度。针对降低干涉配合安装力的研究,也需进一步深化。
在研究初期,有限元分析方法仅用于反映干涉配合关系形成后CFRP孔周应力分布情况和变化规律。例如,宋丹龙等[ 宋丹龙, 宋旭峰, 白洋洋, 等. 碳纤维增强环氧树脂复合材料层合板干涉连接插钉轴向力建模与分析[J]. 复合材料学报, 2019, 36(10): 2294–2301.SONG Danlong, SONG Xufeng, BAI Yangyang, et al. Research on thrust force of carbon fiber reinforced epoxy resin composite laminates during the interference-fit bolt installation process[J]. Acta Materiae Compositae Sinica, 2019, 36(10): 2294–2301. 47]通过建立CFRP干涉连接结构有限元模型及三维插钉有限元模型,研究了不同干涉量对高锁螺栓安装过程中的应力分布的影响,并通过试验验证了模型的正确性,揭示了层合板孔周径向挤压应力分布和插钉轴向力变化规律。Jiang等[ JIANG J F, BI Y B. Effect of parameters on local stress field in single-lap bolted joints with the interference fit[J]. Advances in Mechanical Engineering, 2016, 8(5): 1687814016647255. 48]建立三维复合材料单搭接螺栓连接结构模型,分析干涉量、夹紧力、摩擦系数和搭接几何尺寸等因素对该结构的局部应力场和残余应力的影响。Kim等[ KIM S Y, HE B, SHIM C S, et al. An experimental and numerical study on the interference-fit pin installation process for cross-ply glass fiber reinforced plastics (GFRP)[J]. Composites Part B: Engineering, 2013, 54: 153–162. 49]建立了三维干涉连接结构有限元模型,分析了孔周附近的径向和切向应力分布,发现应力分布随着干涉量的增加而增加。Wu等[ WU T, ZHANG K F, CHENG H, et al. Analytical modeling for stress distribution around interference fit holes on pinned composite plates under tensile load[J]. Composites Part B: Engineering, 2016, 100: 176–185. 50]建立了拉伸载荷下三维有限元模型,讨论了层合板特性、铺层和载荷水平对应力分布的影响。
例如,魏景超等[ 魏景超, 矫桂琼, 闫照明, 等. 单面螺纹抽钉干涉配合复合材料连接件挤压强度研究[J]. 航空学报, 2013, 34(7): 1627–1635.WEI Jingchao, JIAO Guiqiong, YAN Zhaoming, et al. Bearing strength of composite joints interference-fitted with blind bolts[J]. Acta Aeronautica et Astronautica Sinica, 2013, 34(7): 1627–1635. 39]针对单面抽芯铆钉对复合材料干涉配合连接进行了数值模拟研究,探讨干涉配合对复合材料的安装损伤和连接件挤压强度影响;建立的三维有限元模型考虑了钉孔接触、渐进损伤及大变形理论,在失效准则方面使用在Hashin三维失效准则[ HASHIN Z. Fatigue failure criteria for unidirectional fiber composites[J]. Journal of Applied Mechanics, 1981, 48(4): 846–852. 51]基础上发展而来的含非线性因子失效判定准则[ XIAO Y, ISHIKAWA T. Bearing strength and failure behavior of bolted composite joints (part II: Modeling and simulation)[J]. Composites Science and Technology, 2005, 65(7–8): 1032–1043. 52],在性能退化方面使用考虑退化因子的Tan退化准则[ TAN S C, PEREZ J. Progressive failure of laminated composites with a hole under compressive loading[J]. Journal of Reinforced Plastics and Composites, 1993, 12(10): 1043–1057. 53],得到渐进损伤分析流程如图12所示;通过有限元模型研究了0~3%干涉量范围的损伤演变情况,发现0.5%干涉量配合下没有产生干涉损伤,3%的干涉量对孔边单元造成了大量损伤,在静拉伸时降低了连接头强度。通过试验验证了该模型的有效性。
图12 渐进损伤分析流程图[ 魏景超, 矫桂琼, 闫照明, 等. 单面螺纹抽钉干涉配合复合材料连接件挤压强度研究[J]. 航空学报, 2013, 34(7): 1627–1635.WEI Jingchao, JIAO Guiqiong, YAN Zhaoming, et al. Bearing strength of composite joints interference-fitted with blind bolts[J]. Acta Aeronautica et Astronautica Sinica, 2013, 34(7): 1627–1635. 39]
Fig.12 Progressive damage analysis flow chart[ 魏景超, 矫桂琼, 闫照明, 等. 单面螺纹抽钉干涉配合复合材料连接件挤压强度研究[J]. 航空学报, 2013, 34(7): 1627–1635.WEI Jingchao, JIAO Guiqiong, YAN Zhaoming, et al. Bearing strength of composite joints interference-fitted with blind bolts[J]. Acta Aeronautica et Astronautica Sinica, 2013, 34(7): 1627–1635. 39]
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