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Carbon nanofiber reinforced epoxy matrix composites and syntactic foams - mechanical, thermal, and electrical properties.

机译：碳纳米纤维增强的环氧基复合材料和复合泡沫-机械，热和电性能。

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摘要

The tailorability of composite materials is crucial for use in a wide array of real-world applications, which range from heat-sensitive computer components to fuselage reinforcement on commercial aircraft. The mechanical, electrical, and thermal properties of composites are highly dependent on their material composition, method of fabrication, inclusion orientation, and constituent percentages. The focus of this work is to explore carbon nanofibers (CNFs) as potential nanoscale reinforcement for hollow particle filled polymer composites referred to as syntactic foams. In the present study, polymer composites with high weight fractions of CNFs, ranging from 1-10 wt.%, are used for quasi-static and high strain rate compression analysis, as well as for evaluation and characterization of thermal and electrical properties. It is shown that during compressive characterization of vapor grown carbon nanofiber (CNF)/epoxy composites in the strain rate range of 10-4-2800 s-1, a difference in the fiber failure mechanism is identified based on the strain rate. Results from compression analyses show that the addition of fractions of CNFs and glass microballoons varies the compressive strength and elastic modulus of epoxy composites by as much as 53.6% and 39.9%. The compressive strength and modulus of the syntactic foams is also shown to generally increase by a factor of 3.41 and 2.96, respectively, with increasing strain rate when quasi-static and high strain rate testing data are compared, proving strain rate sensitivity of these reinforced composites. Exposure to moisture over a 6 month period of time is found to reduce the quasi-static and high strain rate strength and modulus, with a maximum of 7% weight gain with select grades of CNF/syntactic foam. The degradation of glass microballoons due to dealkalization is found to be the primary mechanism for reduced mechanical properties, as well as moisture diffusion and weight gain. In terms of thermal analysis results, the coefficient of thermal expansion (CTE) of CNF/epoxy and CNF/syntactic foam composites reinforced with glass microballoons decrease by as much as 11.6% and 38.4%. The experimental CTE values for all of the composites also fit within the bounds of established analytical models predicting the CTE of fiber and particle-reinforced composites. Further thermal studies through dynamic mechanical analysis demonstrated increased thermal stability and damping capability, where the maximum use and glass transition temperatures increase as much as 27.1% and 25.0%, respectively. The electrical properties of CNF reinforced composites are evaluated as well, where the electrical impedance decreases and the dielectric constant increases with addition of CNFs. Such behavior occurs despite the presence of epoxy and glass microballoons, which serve as insulative phases. Such results are useful in design considerations of lightweight composite materials used in weight saving, compressive strength, and damage tolerance applications, such as lightweight aircraft structure reinforcement, automobile components, and buoyancy control with marine submersibles. The results of the analyses have also evaluated certain factors for environmental exposure and temperature extremes, as well as considerations for electronics packaging, all of which have also played a role in shaping avant-garde composite structure designs for efficient, versatile, and long-life service use.
机译：复合材料的可定制性对于在各种实际应用中使用至关重要，这些应用包括从热敏计算机组件到商用飞机的机身加固。复合材料的机械，电气和热性能高度依赖于其材料组成，制造方法，夹杂物取向和组成百分比。这项工作的重点是探索碳纳米纤维（CNF）作为潜在的纳米级增强材料，用于填充中空颗粒的聚合物复合材料（称为复合泡沫）。在本研究中，具有高CNF重量分数（范围为1-10 wt。％）的聚合物复合材料用于准静态和高应变率压缩分析，以及热性能和电性能的评估和表征。结果表明，在应变速率范围为10-4-2800 s-1的气相生长碳纳米纤维（CNF）/环氧树脂复合材料的压缩表征过程中，基于应变速率可以识别出纤维破坏机理的差异。压缩分析的结果表明，添加CNF和玻璃微气球的馏分可使环氧复合材料的压缩强度和弹性模量分别变化多达53.6％和39.9％。当比较准静态和高应变率测试数据时，复合泡沫的抗压强度和模量通常也分别增加了3.41和2.96，随着应变率的增加，证明了这些增强复合材料的应变率敏感性。发现在六个月的时间内暴露在湿气中会降低准静态和高应变率强度和模量，对于某些等级的CNF /等规泡沫，最大增重7％。发现由于脱碱而引起的玻璃微气球的降解是降低机械性能以及水分扩散和重量增加的主要机理。在热分析结果方面，用玻璃微气球增强的CNF /环氧树脂和CNF /同规泡沫复合材料的热膨胀系数（CTE）分别降低了11.6％和38.4％。所有复合材料的实验CTE值也符合建立的预测纤维和颗粒增强复合材料CTE的分析模型的范围。通过动态力学分析进行的进一步热研究表明，热稳定性和阻尼性能增强，其中最大使用量和玻璃化转变温度分别增加了27.1％和25.0％。还评估了CNF增强复合材料的电性能，其中添加CNF会降低电阻抗，介电常数会增加。尽管存在用作绝缘相的环氧树脂和玻璃微气球，但仍会发生这种行为。这样的结果在用于减轻重量，抗压强度和损伤容忍性应用的轻质复合材料的设计考虑中很有用，例如轻质飞机结构的加固，汽车部件以及船用潜水器的浮力控制。分析结果还评估了环境暴露和极端温度的某些因素，以及电子封装的考虑因素，所有这些因素在塑造前卫复合结构设计以实现高效，通用和长寿命方面也发挥了作用服务使用。

著录项

  • 作者

    Poveda, Ronald Leonel.;

  • 作者单位

    Polytechnic Institute of New York University.;

  • 授予单位 Polytechnic Institute of New York University.;
  • 学科 Engineering Mechanical.;Plastics Technology.;Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2014
  • 页码 164 p.
  • 总页数 164
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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