| 引用本文: | 刘坤,欧云福,张耘箫,翁宜婷,茅东升.聚醚酰亚胺的微观形貌调控及其层间增韧碳纤维/环氧树脂机理[J].中国表面工程,2024,37(6):462~472 |
| LIU Kun,OU Yunfu,ZHANG Yunxiao,WENG Yiting,MAO Dongsheng.Microscopic Morphology Control of Polyetherimide and its Interlaminar Toughening Mechanisms of Carbon Fiber Reinforced Epoxy Composites[J].China Surface Engineering,2024,37(6):462~472 |
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| 聚醚酰亚胺的微观形貌调控及其层间增韧碳纤维/环氧树脂机理 |
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刘坤1，2，欧云福1，张耘箫1，2，翁宜婷1，2，茅东升1
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1.中国科学院宁波材料工程与技术研究所 宁波 315201 ；2.中国科学院大学材料科学与光电技术学院 北京 100049
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| 摘要: |
| 碳纤维增强树脂基复合材料（CFRP）因其优异的力学性能被广泛应用，但受到层状的结构特性以及树脂本体脆性的影响，其沿厚度方向的承载能力相对较差，易发生分层损伤。通过静电纺丝设备简单有效地将可溶性聚醚酰亚胺（PEI）制备为具有不同微观结构形貌（颗粒和纤维）的薄膜，并将其引入复合材料层间区域进行增韧。测试结果表明，颗粒状 PEI 试样的 I 和 II 型层间断裂韧性较基准样分别提升 18.7%和 19.2%。与之对比，纤维状 PEI 试样展现出更好的增韧效果，其 I 和 II 型层间断裂韧性较基准样分别提升 53.8%和 57.3%。最后通过对断裂面的显微观察，较为系统地研究了其内在增韧机制， 探讨了相形态对增韧效果的影响。 |
| 关键词: 碳纤维增强树脂基复合材料 静电纺丝 层间增韧 颗粒增韧 纤维增韧 |
| DOI：10.11933/j.issn.1007-9289.20240103001 |
| 分类号:TB332 |
| 基金项目:宁波市自然科学基金（2021J208）；中国博士后科学基金（2022M713241）；浙江省领军型创新团队项目（2021R01005）；宁波市“甬江引才工程”（2021A-045-C) |
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| Microscopic Morphology Control of Polyetherimide and its Interlaminar Toughening Mechanisms of Carbon Fiber Reinforced Epoxy Composites |
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LIU Kun1，2，OU Yunfu1，ZHANG Yunxiao1，2，WENG Yiting1，2，MAO Dongsheng1
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1.Ningbo Institute of Materials Technology and Engineering,Chinese Academy of Sciences, Ningbo 315201 , China ；2.College of Materials Science and Opto Electronics Technology,University of Chinese Academy of Sciences, Beijing 100049 , China
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| Abstract: |
| Carbon fiber reinforced polymer (CFRP) composites are widely used owing to their excellent mechanical properties. However, CFRP are affected by the structural characteristics of the ply and brittleness of the resin, and the load-bearing capacity along the thickness direction is relatively poor and susceptible to delamination damage. The delamination sensitivity of laminates remains an important issue that limits their application. Fibers and particles are commonly used as toughening materials for laminates. The high porosity of thermoplastic fiber veils and large specific surface area of the particles enables efficient toughening. Electrostatic spinning and electrostatic spraying are simple and efficient processes for the preparation of these two types of materials, and their working mechanisms are similar; therefore, the same electrostatic spinning equipment can be used to prepare toughened materials with two different morphologies and structures. In this study, polyetherimide (PEI) was selected owing to its toughness, excellent mechanical properties, and good processability. PEI is soluble in common solvents, which facilitates electrostatic spinning and ensures its incompatibility with epoxy resins to preserve the morphology of the toughened layer. In the experiment, different morphologies of toughened layers were prepared by adjusting the concentration of the PEI-DMF spinning solution, and the morphologies of toughened layers were particles and fibers when the concentration of PEI solution was 18% and 30%, respectively. Two interlayers with different morphologies were inserted into the interlayers of carbon fiber fabrics, infused with epoxy resin via the VARTM process, and cured at 80 ℃ for 2 h and 120 ℃ for 2 h under a pressure of 1 MPa to obtain CFRP. Under these conditions, the effects of different toughened layers on the interlaminar fracture properties of the composite laminates were investigated, which successfully improved the mode I and II interlaminar fracture toughness. The mode I interlaminar fracture toughness was increased by 18.7% and 53.8% for PEI 18% and PEI 30%, respectively. The same trend was observed for mode II interlaminar fracture toughness, which was increased by 19.2% and 57.3% for PEI 18% and PEI 30%, respectively. Both fiber-toughened samples maintained a better increase in interlaminar toughness. Specifically, the mode I interlaminar fracture toughness test produced more interlaminar crossovers in the delamination paths of the fiber-toughened samples, and these crossovers were critical for creating nanofiber bridging zones, which resulted in greater energy dissipation. The crack extension paths revealed that the modified materials are more zigzagged, which also suggests a greater energy dissipation for both samples. Moreover, after the addition of the toughened layer, the surface of the fractured single carbon fiber was covered with a resin matrix instead of the original smooth surface, indicating the improved bonding of the resin matrix to the carbon fiber surface after the addition of PEI. In the mode I interlaminar fracture toughness test, the particles were dispersed in the epoxy resin, and the cracks were hindered by the particles during crack propagation, leading to particle yielding, pinning, and crack deflection and thereby increasing energy dissipation. However, because the particles are discontinuous, the cracks extend along the pure resin area when they extend to the area without particles. Hence, a better toughening effect cannot be achieved. Similarly, in the mode II interlaminar fracture toughness test, because of the discontinuities in the particles, the crack extension is more biased to pass through the resin matrix between the particles as it passes through the toughened layer, and fewer particles are involved in energy dissipation, which results in less enhancement of the mode II interlaminar fracture toughness. For the continuous fiber-toughened layer, in the mode I interlaminar fracture test, crack expansion was more biased in the pure resin-filled area, which was hindered by the fiber to produce a more zigzag expansion path and therefore consumed more energy. For the mode II interlaminar fracture toughness test, owing to the continuity of the fibers, cracks in the expansion of the interlayer crossing the middle layer must destroy more fibers. The fiber breakage, pull-outs, etc., result in further energy consumption. Notably, during the mode I interlaminar fracture toughness test, the load of the fiber-toughened sample has a sudden drop and is close to the baseline. After polishing the samples, it was observed that the cracks completely deviated from the toughened zone, which affected the enhancement of the interlaminar toughness by the fiber-toughened layer. Moreover, the interlaminar fracture toughness test of the composites and analysis of the scanning electron microscopy images of the fracture surfaces revealed that toughening effects can be achieved using thermoplastic resin. PEI maintained its morphology in the epoxy, and there was some bonding between the PEI and epoxy. However, the changes in the morphology of the toughened layer led to two completely different toughening effects. Although the interlayer properties of particles and fibers have been explored in other studies, enhancing the interlayer properties of the same material under the same process requires consideration of the effects of interlayer morphology. Hence, this study adopted a systematic and scientific approach to compare the effects of the two morphologies on the interlayer toughness. The results of this study provide referential significance. |
| Key words: carbon fiber reinforced resin matrix composites (CFRP) electrospinning interlaminar toughening particle toughening fiber toughening |
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