Mode I interlaminar fracture toughness measurement of PBO fiber reinforced epoxy composites by DIC technology
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摘要: I型双悬臂梁(DCB)试验通常用于单向复合材料的层间抗拉性能研究,目标是测量I型层间断裂韧性,其可作为复合材料分层扩展及失效机制研究的重要输入参数。在DCB试验中必须经常暂停试验以实现多次测量裂纹长度,这不仅会对裂纹传播产生潜在影响,造成测量误差且多次反复试验的时效性较差。数字图像相关(DIC)测试技术应用于裂纹扩展长度测量具有实时跟踪、精确定位的优点,可有效提高I型断裂韧性试验的测量效率,但应用于非连续变形行为仍存在局限性,且易受到图像噪声的干扰,产生测量误差。本文发展了一种基于DIC测试技术的实时获取裂纹长度的检测方法,通过图像匹配算法获取试件的非连续变形位移场,并提出一种根据全局横向位移离散程度的辨别方法,实现了裂纹尖端的实时捕捉。再通过DCB试验,与传统测量方式对比,裂纹长度的测量误差平均不超过2.76%,验证了该方法的准确性和高效性,同时也克服了聚对苯撑苯并双噁唑 (PBO)/环氧树脂复合材料侧表面毛糙、散斑质量较差及纤维桥接对测量结果的干扰,最终获取了有效的I型层间断裂韧性初始值及稳态扩展值。Abstract: The mode I double cantilever beam (DCB) test was commonly applied to investigate the material resistance to crack propagation in unidirectional composites, aiming at obtaining the interlaminar fracture toughness in mode I, which was an important input parameter for the study of delamination propagation and failure mechanism of composite materials. The DCB test must be suspended frequently for the multiple measurements of the crack length, which will not only have a potential effect on the propagation of crack and even lead to the measurement error, but also can be a time and effort consuming process. Digital image correlation (DIC) technology applied to crack propagation length measurement has the advantages of real-time tracking and precise positioning, effectively improving the measurement efficiency of the mode I fracture toughness, but it still has limitation when applied to discontinuous deformation behavior, and it is susceptible to interference from image noise, resulting in measurement error. This paper developed a real-time crack length detection method based on DIC and obtained the discontinuous deformation displacement field of the specimen through an image matching algorithm, and then proposed an identification method based on the degree of dispersion of the global lateral displacement, which realized the crack tip real-time capture. Then, compared with the traditional measurement method in the DCB test, the measurement error of the crack length does not exceed 2.76% on average, which verifies the accuracy and efficiency of the method, meanwhile, overcomes the measurement interference caused by roughness of the side surface, the poor speckle quality and the fiber bridging of the poly p-phenylene-2,6-benzoxazole (PBO)/epoxy composites. Finally, the effective initial value and steady-state propagation value of the mode I interlaminar fracture toughness.
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Key words:
- DIC /
- PBO/epoxy composites /
- crack length /
- DCB test /
- fiber bridging /
- fracture toughness
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表 1 PBO/环氧树脂复合材料不同时刻裂纹长度测量误差
Table 1. Crack length measurement error of PBO/epoxy composites at different moments
Time/min Magnifying glass/mm DIC/mm Deviation
/%5 71.8 70.0 1.80 10 90.8 87.2 3.60 15 106.8 104.9 1.70 20 112.3 115.2 2.50 25 130.9 126.1 3.67 30 143.2 138.5 3.28 Avg — — 2.76 Note: Avg—Average. 表 2 不同测量方式下PBO/环氧树脂复合材料I型断裂韧性
Table 2. Mode I fracture toughness of PBO/epoxy composites under different measurement methods
Number Method GI_Initial/
(N·mm−1)GI_Stable/
(N·mm−1)Toughening/% 01 Magnifying glass 0.28887 0.804077 278.35 01 DIC 0.28851 0.910412 315.56 Deviation — 0.125% 13.22% — 02 Magnifying glass 0.31208 0.931708 298.55 02 DIC 0.28682 0.904918 315.50 Deviation — 8.09% 2.88% — 03 Magnifying glass 0.30290 0.744596 245.82 03 DIC 0.28658 0.751677 262.29 Deviation — 5.39% 0.95% — -
[1] SO Y H. Rigid-rod polymers with enhanced lateral interactions[J]. Progress in Polymer Science,2000,25(1):137-157. doi: 10.1016/S0079-6700(99)00038-6 [2] HU X D, JENKIN S E, MIN B G, et al. Rigid-rod polymers: Synthesis, processing, simulation, structure, and properties[J]. Macromolecular Materials and Engineering,2003,288(11):823-843. doi: 10.1002/mame.200300013 [3] CHAE H G, KUMAR S. Rigid-rod polymeric fibers[J]. Journal of Applied Polymer Science,2006,100(1):791-802. doi: 10.1002/app.22680 [4] HU C, WANG F, YANG H Y, et al. Preparation and characterization of poly p-phenylene-2, 6-benzobisoxazole fiber-reinforced resin matrix composite for endodontic post material: A preliminary study[J]. Journal of Dentistry,2014,42(12):1560-1568. doi: 10.1016/j.jdent.2014.10.007 [5] OMBRES L. Structural performances of reinforced concrete beams strengthened in shear with a cement based fiber composite material[J]. Composite Structures,2015,122:316-329. doi: 10.1016/j.compstruct.2014.11.059 [6] 王倩, 顾轶卓, 刘宁, 等. PBO纤维与环氧树脂界面粘结性能及其影响因素研究[J]. 玻璃钢/复合材料, 2018(12):28-35.WANG Qian, GU Yizhuo, LIU Ning, et al. Studies on interfacial bonding property and influencing factors of PBO fiber and epoxy resin[J]. Fiber Reinforced Plastics/Composites,2018(12):28-35(in Chinese). [7] MI Y, CRISFIELD M A, DAVIES G A O, et al. Progressive delamination using interface elements[J]. Journal of Composite Materials,1998,32(14):1246-1272. doi: 0.1177/002199839803201401 [8] XU W, WAAS A M. Multiple solutions in cohesive zone models of fracture[J]. Engineering Fracture Mechanics,2017,177:104-122. doi: 10.1016/j.engfracmech.2017.03.026 [9] GONG Y, ZHAO L, ZHANG J, et al. Delamination propagation criterion including the effect of fiber bridging for mixed-mode I/II delamination in CFRP multidirectional laminates[J]. Composites Science & Technology,2017,151:302-309. doi: 10.1016/j.compscitech.2017.09.002 [10] American Society for Testing and Materials. Standard test method for mode I interlaminar fracture toughness of unidirectional fiber-reinforced polymer matrix composites: ASTM D5528—2013[S]. West Conshohocken: ASTM International, 2013. [11] ZHU J, GAO Z. Research on crack measurement technique in solids material with digital image correlation (DIC)[C]//Key Engineering Materials. Sanya: Trans Tech Publications Ltd., 2007, 353: 2606-2610. [12] ALBERTSEN H, TVENS J, PETERS P, et al. Interlaminar fracture toughness of CFRP influenced by fibre surface treatment: Part 1. Experimental results[J]. Composites Science and Technology,1995,54(2):133-145. doi: 10.1016/0266-3538(95)00048-8 [13] ARAKAWA K, ISHIGUM M, TAKAHASHI K. Study of mode I interlaminar fracture in CFRP laminates by moiré interferometry[J]. International Journal of Fracture,1994,66(3):205-212. doi: 10.1007/BF00042584 [14] PERRY K E, MCKELVIE J. Measurement of energy release rates for delaminations in composite materials[J]. Experimental Mechanics,1996,36(1):55-63. doi: 10.1007/BF02328698 [15] COLAVITO K, MADENCI E. Adhesive failure in hybrid double cantilever beams by digital image correlation[C]//51st AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference. Orlando, 2010: 2603. [16] MATTHIAS M, LOUISE A P, TIM F. Measurements of mode I interlaminar properties of carbon fiber reinforced polymers using digital image correlation[C]//Key Engineering Materials. Sanya: Trans Tech Publications Ltd, 2017, 742: 652-659. [17] MURRAY B R, FONTEYN S, CARRELLA-PAYAN D, et al. Crack tip monitoring of mode I and mode II delamination in CF/epoxies under static and dynamic loading conditions using digital image correlation[J]. Proceedings,2018,2(8):389. [18] KHUDIAKOVA A, WOLFAHRT M, GODEC D, et al. Determination of the mode I strain energy release rate in carbon fiber reinforced composites by means of digital image correlation technique[C]//18th European Conference on Composite Materials. Athens, Greece, 2018. [19] REINER J, TORRES J P, VEIDT M. A novel top surface analysis method for mode I interface characterisation using digital image correlation[J]. Engineering Fracture Mechanics,2017,173:107-117. doi: 10.1016/j.engfracmech.2016.12.022 [20] ZHU M, GORBATIKH L, FONTEYN S, et al. Digital image correlation measurements of mode I fatigue delamination in laminated composites[C]//Multidisciplinary Digital Publishing Institute Proceedings. Switzerland: MDPI AG, 2018, 2(8): 430. [21] MALLON S, KOOHBOR B, KIDANE A, et al. Fracture behavior of prestressed composites subjected to shock loading: A DIC-based study[J]. Experimental Mechanics,2015,55(1):211-225. doi: 10.1007/s11340-014-9936-5 [22] 杜鉴昕, 赵加清, 王海涛, 等. 一种针对裂尖变形场测量的正则化全局DIC方法[J]. 光学学报, 2020, 40(11):1112001. doi: 10.3788/AOS202040.1112001DU Jianxin, ZHAO Jiaqing, WANG Haitao, et al. Regularized global digital image correlation method for crack tip deformation field measurement[J]. Acta Optica Sinica,2020,40(11):1112001(in Chinese). doi: 10.3788/AOS202040.1112001 [23] LIU C, CADY C M, RAE P J, et al. On the quantitative measurement of fracture toughness in high explosive and mock materials[C]//14th International Detonation Symposium. Idaho, 2010. [24] HASSAN G M. Deformation measurement in the presence of discontinuities with digital image correlation: A review[J]. Optics and Lasers in Engineering,2021,137:106394. doi: 10.1016/j.optlaseng.2020.106394 [25] KHUDIAKOVA A, GRASSER V, BLUMENTHAL C, et al. Automated monitoring of the crack propagation in mode I testing of thermoplastic composites by means of digital image correlation[J]. Polymer Testing,2020,82:106304. doi: 10.1016/j.polymertesting.2019.106304 [26] ZHU M, GORBATIKH L, FONTEYN S, et al. Digital image correlation assisted characterization of mode I fatigue delamination in composites[J]. Composite Structures,2020,253:112746. doi: 10.1016/j.compstruct.2020.112746 [27] GARCIA D, ORTEU J J, PENAZZI L. A combined temporal tracking and stereo correlation technique for accurate measurement of 3D displacements: Application to sheet metal forming[J]. Journal of Materials Processing Technology,2002,125-126:736-742. doi: 10.1016/S0924-0136(02)00380-1 [28] BLABER J, ADAIR B, ANTONIOU A. NCORR: Open-source 2D digital image correlation matlab software[J]. Experimental Mechanics,2015,55(6):1105-1122. doi: 10.1007/s11340-015-0009-1 [29] PAN B, ASUNDI A, XIE H, et al. Digital image correlation using iterative least squares and pointwise least squares for displacement field and strain field measurements[J]. Optics & Lasers in Engineering,2009,47(7-8):865-874. doi: 10.1016/j.optlaseng.2008.10.014