聚合物基复合材料导热性的研究

讨论了聚合物基高导热高绝缘纳米复合材料的导热机理与常用的导热理论模型。考虑到填充率、温度等的影响，采用不同理论模型计算了用氧化铝纳米颗粒填充环氧树脂时材料的热导率，并结合相关研究实验对不同导热理论模型进行了分析比较。     

聚合物复合材料导热性能的研究

论述了填充聚合物复合材料的导热性及其变化规律；总结了复合材料导热的理论模型和导热系数预测方程，对比研究了各种导热模型的区别与联系；分析了影响复合材料导热特性的因素。     

填充型聚合物基复合材料的导电和导热性能

研究了高密度聚乙烯为基体、炭黑和炭纤维为填料复合体系的导电和导热性能。发现当导电填料的含量达到渗流阈值时,复合材料的电导率急剧升高;而在渗流阈值附近,其热导率未出现突变。这表明电导渗流现象不完全是由导电粒子通过物理接触生成导电链所致。其导电机制是相当数量的导电粒子相互发生隧道效应。     

聚合物纳米石墨烯复合材料导热性能研究进展

集成电路伴随着电子、航天和航空领域的发展而快速发展,但往往伴随着散热困难的问题,影响着使用效率和仪器寿命。从质量、耐蚀性、加工工艺和成本等方面考虑,聚合物复合材料是导热材料中最具发展前景的材料。然而聚合物固有的导热率非常低,因此,提高聚合物的导热率对于其在这些领域的应用显得非常重要,这在过去的20年中已经成为一个非常重要的研究课题。主要从以下两个方面进行介绍:(1)从分子链形态、链结构和链间耦合3个方面分析总结了聚合物的微观导热机理;(2)重点介绍近年来石墨烯填充聚合物纳米复合材料导热性能的主要研究进展以及未来的研究挑战。     

导热型碳纤维增强聚合物基复合材料的研究进展

综述了导热型连续碳纤维增强聚合物基复合材料(CFRP)的研究与应用现状和进展,阐述了CFRP的声子导热和光子导热机理,介绍了不同铺层角度和铺层比的CFRP面内和厚度方向热导率计算模型及测试方法,分析了环氧树脂、氰酸酯、双马来酰亚胺等3类树脂体系和聚丙烯腈基(PAN)碳纤维、中间相沥青基碳纤维、气相生长碳纤维、碳纳米管纤维等4类增强体以及工艺方法等因素对CFRP热导率的影响。     

粒子填充聚合物基复合材料导热性能的数值模拟

根据电镜照片中观察的微观结构信息,基于两套新设计的算法建立了代表体积元(RVE)模型,基于此模型研究了粒子填充聚合物基复合材料的导热性能与微观结构的关系。通过对电镜照片的处理得到两个参数即稀疏区比重和稀疏区半径,建立了与实际体系相符的具有非均匀粒子分布结构的 RVE模型。制备了氧化铝/高温硫化硅橡胶导热复合材料,并测试了不同填充量下体系的热导率,用以验证模型的有效性。采用有限元方法求解RVE模型得到的热导率预测值与实验值进行对比,结果表明：填料用量在宽范围内预测结果与实验值均吻合很好; 与均匀分布或随机分布相比,存在稀疏区和富集区的非均匀分布的体系具有更高的热导率,这种差异在高填充量下当颗粒间形成导热网链时更为显著;在相同填充量下,不同的粒子空间分布结构可使体系热导率差别很大,是影响体系热导率的关键因素。     

聚合物基复合材料的界面结构与导热性能

在整理近年来国内外对聚合物基导热复合材料性能的研究工作的基础上,总结界面结构与界面处理对聚合物基复合材料界面和导热性能的影响,分析目前已有研究中的缺点和不足,提出未来改善界面结合、提高聚合物基复合材料导热性能的具体方法,并指出探究界面结构与热流散射的关系,特别是弱界面结合情况下的热流传导规律,对提高聚合物基复合材料的热导率有很大的指导意义。     

聚合物基导热复合材料研究进展

概述了聚合物基导热复合材料的应用开发背景,从理论上阐述了聚合物基导热复合材料的导热机理及导热理论模型.综述了国内外聚合物基导热复合材料研究开发状况,提出了今后的研究方向.     

热传导聚合物基复合材料的研究进展

本文主要介绍了聚合物基复合材料的导热机理 ,以及预测二相体系复合材料热导率的理论模型方程。同时介绍了聚合物基导热材料的 3种类型及其具体应用 ,并提出聚合物基导热材料现阶段值得开发的课题和研究方向     

The effect of longitudinal heat conduction on a regenerative heat exchanger

Abstract

This study is to discuss the effect of longitudinal heat conduction on a rotary regenerative heat exchanger. An example in Ref. [5] is computed to compare the effect of longitudinal heat conduction. The solutions presented in this study are obtained from the method of numerical analysis as shown in Ref. [3].     

A hybrid flux model for heat conduction problems

A hybrid method of solution for the linear problem of heat conduction in a body is presented. The variational support is a two‐field functional whose arguments are heat flux, which meets a priori inner thermal equilibrium, and temperature on the boundary of the body. The stationary conditions of the functional are the Fourier's law and the prescribed boundary conditions. This variational framework allows to develop a finite element model that exhibits good accuracy, especially in the presence of geometry irregularities in a mesh. Copyright © 2000 John Wiley & Sons, Ltd.     

Application of photoacoustic and photothermal techniques for heat conduction measurements in a free-standing chemical vapor-deposited diamond film

Heat conduction in a free-standing chemical vapor-deposited polycristalline diamond film has been investigated by means of combined front and rear photoacoustic signal detection techniques and also by means of a “mirage” photothermal beam deflection technique. The results obtained with the different techniques are consistent with a value of α=(5.5±0.4)×10⁻⁴ m² · s⁻¹ for thermal diffusivity, resulting in a value ofκ=(9.8±0.7)×10² W·m⁻¹·K⁻¹ for thermal conductivity when literature values for the density and heat capacity for natural diamond are used.     

Characterization of defects in carbon fiber-reinforced plastics by inverse heat conduction analysis using transfer matrix between layers

In this study, inverse analyses of the defects in carbon fiber-reinforced plastics (CFRPs) are performed using the transfer matrix approach. The material properties used in the calculation were obtained on the basis of mixture laws for epoxy resin and carbon fibers. The accuracy of the inverse analysis was confirmed by calculations employing numerical models of CFRP plates with PAN-based and pitch-based carbon fibers containing defects. The inverse analysis was conducted based on the temperature distribution of CFRP laminates with PAN-based carbon fibers, which was obtained by infrared measurements. The analyses successfully estimated the positions of defects, and the effectiveness of the transfer matrix method for CFRPs was demonstrated through the inverse analysis.     

Simulation of transient heat conduction using one‐dimensional mapped infinite elements

Many engineering problems exist in physical domains that can be said to be infinitely large. A common problem in the simulation of these unbounded domains is that a balance must be met between a practically sized mesh and the accuracy of the solution. In transient applications, developing an appropriate mesh size becomes increasingly difficult as time marches forward. The concept of the infinite element was introduced and implemented for elliptic and for parabolic problems using exponential decay functions. This paper presents a different methodology for modeling transient heat conduction using a simplified mesh consisting of only two‐node, one‐dimensional infinite elements for diffusion into an unbounded domain and is shown to be applicable for multi‐dimensional problems. A brief review of infinite elements applied to static and transient problems is presented. A transient infinite element is presented in which the element length is time‐dependent such that it provides the optimal solution at each time step. The element is validated against the exact solution for constant surface heat flux into an infinite half‐space and then applied to the problem of heat loss in thermal reservoirs. The methodology presented accurately models these phenomena and presents an alternative methodology for modeling heat loss in thermal reservoirs. Copyright © 2010 John Wiley & Sons, Ltd.     

非连续增强钛基复合材料的热处理研究进展

综述了非连续增强钛基复合材料热处理的研究现状,主要分析了热处理工艺对复合材料微观组织与力学性能的影响,提出了当前研究中存在的问题和今后潜在的发展方向.     

A finite element method for non-Fourier heat conduction in strong thermal shock environments

Non-Fourier effect is important in heat conduction in strong thermal environments. Currently, generally-purposed commercial finite element code for non-Fourier heat conduction is not available. In this paper, we develop a finite element code based on a hyperbolic heat conduction equation, which includes the non-Fourier effect in heat conduction. The finite element space discretization is used to obtain a system of differential equations for the time. The transient responses are obtained by solving the system of differential equations, based on the finite difference, mode superposition, or exact time integral. The code is validated by comparing the numerical results with exact solutions for some special cases. The stability analysis is conducted and it shows that the finite difference scheme is an ideal method for the transient solution of the temperature field. It is found that with mesh refining (decreasing mesh size) and/or high-order elements, the oscillation in the vicinity of sharp change vanishes, and can be essentially suppressed by the finite difference scheme. A relationship between the time step and the space length of the element was identified to ensure that numerical oscillation vanishes.     

纤维增强热固性聚合物基复合材料层间增韧研究进展

综述了纤维增强热固性聚合物基复合材料（PMC）层间增韧的最新研究进展。热固性复合材料由于基体树脂高的交联密度而呈脆性,表现出低的冲击损伤阻抗和损伤容限特征。柔性聚合物层间增韧是改善聚合物基复合材料层间断裂韧性和抗冲击性的有效手段,且不会降低热固性树脂的热性能和高模量。目前有3种层间增韧方法：颗粒增韧、聚合物纤维增韧和薄膜增韧。讨论了3种方法的概念、实施方案、增韧机理及研究成果。最后重点阐述了创新性的复合材料“离位”增韧思想,介绍了具有全部自主知识产权的“离位”复合材料高性能化技术体系,包括预浸料和液态成型两大复合材料产品系列。     

纤维增强聚合物基复合材料的低温性能

对纤维增强聚合物基复合材料在低温领域的实际应用进行了分类介绍,通过对纤维增强聚合物基复合材料的低温性能、性能影响因素和作用机理、低温应用安全性等方面的研究工作进行总结,突出各类纤维增强聚合物基复合材料低温下的性能优势,阐明了材料性能的不足之处及相应改进措施.对于实际低温应用中纤维增强聚合物基复合材料的选择、性能设计优化,系统安全性的增强提供了参考作用.