结构阻尼树脂基复合材料的结构与性能研究

发布时间：2018-01-19 14:08

本文关键词： 结构阻尼复合材料离位增韧尼龙无纺布芳纶无纺布 PVDF VGCF FEM　出处：《浙江大学》2015年博士论文　论文类型：学位论文

【摘要】：近年来,随着航空航天飞行器向高速、轻质和多功能化方向发展,传统结构材料在减重和减振降噪方面面临着更大的挑战。尤其随着纤维增强复合材料在航空航天领域应用比重的迅速提升,开发兼具高力学性能和振动阻尼性能的新型结构-阻尼复合材料成为研究的热点之一。结构阻尼复合材料属于结构功能一体化复合材料之一,其应用范围涉及航天航空、交通运输、电力电子以及仪器仪表等工业领域,对于国家经济的发展和人们生活质量的提高起到重要的作用。传统的结构阻尼复合材料制备是将结构材料与高阻尼的黏弹性材料粘合在一起。由结构材料提供强度和刚度,黏弹性材料提供阻尼性能。这种复合方式目前暴露出的主要问题是结构的力学性能和耐热性能的下降及工艺性和服役性变差。而最新发展的其他共固化复合材料(蜂窝、智能材料、金属泡沫、纳米材料)又存在增厚增重大、工艺复杂和成本增加的弊端。结构阻尼材料研制中关键问题是选择与结构层匹配的阻尼层材料并能形成很好的界面结构。从材料层面来说,一方面阻尼层材料应与结构层树脂具有较好的界面结合力和不冲突的成型工艺,另一方面阻尼层应具有相对较高的力学性能、阻尼性能和耐热性能。从结构层面来说,结构层和阻尼层最好形成互穿网络结构,这样能减少界面处应力集中,同时改善应力的传递效率,充分发挥阻尼层的阻尼效果。此外,材料的阻尼性能和断裂韧性关系密切,相对成熟的增韧技术可用于结构阻尼复合材料的开发,尤其是通过力学性能优异的热塑性聚合物离位增韧复合材料和纳米级碳材料如纳米碳纤维、碳纳米管等增韧均可以在保证复合材料力学性能的前提下明显提高其断裂韧性。因此,本论文的基本思路即是从材料层面上筛选与基体树脂相匹配且具有较好离位增韧效果的几种多孔的热塑性树脂无纺布(本文选用尼龙和芳纶两种无纺布)作为阻尼材料和离位增韧材料,通过与基体树脂在复合材料的层间形成多相连续的互穿网络结构,在离位增韧改性的同时提高复合材料的阻尼性能。同时,为进一步提高体系的阻尼性能和断裂韧性,通过筛选将结晶型热塑性聚合物PVDF和纳米碳材料VGCF负载在无纺布材料上,研究不同增韧和阻尼材料的协同增韧和阻尼改性效果。另外,考虑到近年来绿色复合材料的发展越来越受到人们的重视,而结构阻尼材料的开发中也应考虑绿色环保的设计原则,本文还筛选了力学性能和阻尼性能相对较好的苎麻纤维和黄麻纤维来制备绿色结构阻尼复合材料。由于阻尼层的加入方式和阻尼性能对结构阻尼材料的整体阻尼性能有直接影响,为进一步研究其变化规律,本论文在实验的基础上对结构阻尼复合材料的两种阻尼测试过程进行了有限元模拟分析。通过ANSYS软件建立了结构阻尼复合材料的阻尼因子和模态频率的虚拟测试方法,通过改变阻尼层的各物理属性可以非常方便的考察阻尼层的变化对复合材料整体性能的影响。这种通过有限元分析建立的虚拟测试技术具有很强的实用性能,可以大大缩短了材料开发的时间周期,为结构阻尼材料的研究提供方便。本论文研究主要得到以下结论：1)尼龙无纺布能够在离位增韧复合材料的同时明显提高复合材料的损耗因子且不会造成复合材料力学性能的明显下降。其中,复合材料的阻尼性能和力学性能与阻尼层的位置和体积分数密切相关。通过在尼龙无纺布上负载PVDF能进一步明显提高共固化复合材料的振动衰减性能和层间断裂韧性,插入7层时损耗因子达到0.0121,比空白样品提高了152.1%,其GⅠC和GⅡC分别达到1700.0J/m2和2829.0J/m2,较空白样品提高了4.6倍和2.9倍。通过在尼龙无纺布上负载PVDF/VGCF能进一步提高结构阻尼复合材料的耐热性能、高温段阻尼性能、导电性能,但对复合材料的力学性能没有明显提高,这可能与纳米材料的分散性差、容易团聚有关。2)芳纶无纺布同样能够在不明显降低复合材料的力学性能的前提下同步提高复合材料的断裂韧性和阻尼性能。与尼龙无纺布相比,ANF离位增韧结构阻尼复合材料的力学性能更好,但界面结合性相对较差,I型、II型层间断裂韧性和CAI较低,但界面阻尼作用反而较高。3)通过苎麻纤维布／碳纤维布／玻璃纤维布的混杂铺层能够平衡力学性能和阻尼性能之间的矛盾,实现材料阻尼性能和力学性能的可控调节,充分发挥复合材料可设计性强的优势。其中"RCRCR"铺层的复合材料的损耗因子达到0.0057,比纯碳纤维布复合材料的0.0018提高了2.2倍,而拉伸强度达到381.6MPa,比纯苎麻纤维板提高了4.6倍。"RCRCR"型复合材料的损耗因子达到0.0101,比纯玻璃纤维布复合材料提高了1.4倍,而拉伸强度达到278MPa,比纯苎麻纤维板提高了3倍多。4)利用ANSYS软件建立了两种虚拟阻尼性能测试方法即虚拟自由振动衰减法和虚拟强迫共振扫频法。通过对两类结构阻尼复合材料的阻尼因子、共振频率及模态损耗因子的实测结果与虚拟测试结果对比,验证了有限元模拟的可行性,同时对不同的混杂铺层方式和阻尼层不同的物理性能对结构阻尼复合材料的阻尼性能的影响进行了研究。结果表明,混杂铺层复合材料的刚度与最外层材料的模量密切相关,而阻尼性能与阻尼层的体积分数和分布有关,当其位于正应力和剪切力最大的表面和中性面时能够发挥最大的阻尼效果。
[Abstract]:In recent years, along with the development of aerospace vehicles to high-speed, lightweight and multifunctional development of traditional structural materials are facing greater challenges in weight loss and reduction. Especially with fiber reinforced composite materials in aerospace applications rapidly enhance the proportion of the new structure, develop both performance and vibration damping properties of high mechanical damping the composite material has become one of the hot research. Structural damping composites belongs to the composite integrated structure and function of the application scope of aerospace, transportation, power electronics and instrumentation industries, an important role for the development of national economy and improvement of people's quality of life. The traditional structural damping composites the preparation is structural materials and high damping viscoelastic materials together. The structure provided by the material strength and stiffness of viscoelastic material. For the main problem of the composite damping performance. The exposed is the mechanical properties and heat resistance of the structure and process of the decline and the service becomes poor. And the latest development of other co cured composite (cellular, intelligent materials, metal foam, nano materials) has increased thickening of major, complex process and defects the increased cost of structural damping material in the development. The key problem is the selection and structure layer, damping layer material and can form a good interface structure. From the material level, a damping layer material and structure layer of resin has good adhesion and conflict forming process, on the other hand, the damping layer should be with relatively high mechanical properties, damping properties and heat resistance. From the aspect of structure, structure layer and damping layer is preferably formed of interpenetrating network structure, this can reduce the stress concentration at the interface, at the same time improve The stress transfer efficiency, give full play to the damping effect of the damping layer. In addition, the relationship between damping properties and fracture toughness of the material closely, the relatively mature toughening technology can be used for the development of structural damping composites, especially the excellent mechanical properties of thermoplastic polymer from a composite toughening and nano carbon materials such as carbon nano fiber, carbon nanotubes can significantly improve the toughening in ensuring the premise of fracture toughness of composite mechanical properties. Therefore, the basic idea of this paper is to select some porous matrix resin and match out of position and has good toughening effect from the material level of thermoplastic resin and aromatic nylon non-woven (this selection two) as a non-woven aramid damping material and ex situ toughening materials, and through the formation of matrix resin in the composite layer between the interpenetrating network structure is continuous, in the off position by At the same time toughening modification to improve the damping properties of the composites. At the same time, in order to further improve the damping properties and fracture toughness of the system, through the screening of the crystalline thermoplastic polymer PVDF and nano carbon materials VGCF load in non-woven materials, research different toughening and damping material synergitic toughening and damping modification effect. In addition, considering the recent development of green composites are more and more attention, and the development of structural damping material also should consider the design principles of green environmental protection, the paper also selected relatively good mechanical properties and damping properties of ramie fiber and jute fiber to produce green structural damping composites due to the effect of damping layer. The addition method and the damping properties of structural damping material overall damping performance, for further study on the regularity of the complex structure of the damping on the basis of experiment A finite element simulation analysis of two kinds of composite damping test process. Through the ANSYS software to build a virtual test method of structural damping composite damping factor and modal frequency, by changing the physical properties of the damping layer can affect the change of damping layer is very convenient to study the overall performance of the composite material has very practical performance. The virtual test technology that through the finite element analysis of the material, can greatly shorten the development cycle time, to provide convenience for the study of structural damping materials. This paper mainly gets the following conclusions: 1) to nylon non-woven fabric decreased significantly in the ex situ toughening composite material increases while the loss factor of composite material and not due to the mechanical properties of the composites. The composites damping properties and mechanical properties and damping layer position and volume fraction. Cut through. In the nylon non-woven fabric can further improve the load of PVDF co curing composite vibration attenuation performance and interlaminar fracture toughness, 7 layer insertion loss factor reached 0.0121, 152.1% higher than the blank sample, the C G I and G II C reached 1700.0J/m2 and 2829.0J/m2, increased by 4.6 compared with the blank sample and 2.9 times. Through the nylon non-woven fabric loaded with PVDF/VGCF can further improve the heat resistance of structural damping composites, conductive properties of damping properties, high temperature, but the mechanical properties of the composites did not increase obviously with the dispersion of nano materials is poor, easy to agglomerate on.2 aramid fiber non-woven fabric can also sync) to improve the fracture toughness and damping properties of the composite materials without significantly decreased the mechanical properties of the composites. Compared with nylon fabric, ANF ex situ toughening structural damping composite material The better mechanical performance, but the interface is relatively poor, I type, II type and CAI interlaminar fracture toughness is low, but the interface damping effect of higher.3) by the mixed layer of ramie cloth / carbon fiber / glass fiber cloth can balance the contradiction between the mechanical properties and damping properties, controllable damping the performance and the mechanical properties of the material regulation, give full play to the advantages of design and strong composite materials. The loss factor of composite RCRCR layer reached 0.0057, more than 0.0018 pure carbon fiber composite material was increased by 2.2 times, while the tensile strength is 381.6MPa, than the pure ramie fiber board is increased by 4.6 times ". The loss factor of RCRCR type composite reached 0.0101, than the pure glass fiber composites increased 1.4 times, while the tensile strength reached 278MPa, increased 3 times more.4 than pure ramie fiber board) to establish two kinds of virtual using ANSYS software Testing method for damping properties of virtual free vibration attenuation method and virtual forced resonance frequency sweep method. The damping factor of two kinds of structural damping composites, comparing the measured results of resonance frequency and the modal loss factor and virtual test results, verify the feasibility of finite element simulation, and the influence of different damping properties of hybrid layer and the physical properties of different damping layer on structural damping composites were studied. The results show that the hybrid composite stiffness and the outer layer material modulus is closely related to the volume fraction and distribution of damping capacity and damping layer, when it is located in the normal stress and the maximum shearing force the surface and the neutral surface can play a damping effect is the biggest.

【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：V214.8;TB33

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