碳纤维复合材料湿膨胀系数试验方法

提出了一种复合材料湿膨胀系数的测定方法，讨论了影响复合材料湿膨胀系数的因素，通过对Ｔ３００－３２３１复合材料吸湿规律的试验研究，验证了该方法。结果表明，该方法可以很好地用于碳纤维增强复合材料的湿膨胀系数的试验研究。     

真空热循环对单向M40J/5228A复合材料质损率和线膨胀系数的影响

对单向M40J/5228A复合材料进行了真空热循环试验 ( 93~413 K,10-5Pa)。分别测试了经不同次数真空热循环后材料的质损率及线膨胀系数。通过所建二维细观损伤模型分析了真空热循环次数对材料线膨胀系数曲线影响的原因。试验结果表明,随真空热循环次数的增加,质损率增大,并经约48次真空热循环后趋于平缓;横向线膨胀系数随温度升高而线性增大,真空热循环次数对其没有影响;纵向线膨胀系数在原始状态时随温度升高而线性减小,经113次真空热循环后表现出先下降后上升的非线性特征,真空热循环次数对纵向线膨胀系数的影响,与界面脱粘程度和残余应力的消除密切相关。      

湿热环境对碳纳米管复合材料界面应力传递的影响

基于碳纳米管的热膨胀系数及弹性模量分别为温度变化的函数,基体的热、湿膨胀系数及弹性模量分别为温度变化和湿度变化的函数,应用连续介质力学的经典弹性壳理论及传统纤维拉拔模型,分析了湿热环境对碳纳米管复合材料界面应力传递的影响。数值计算表明,湿度、温度的效应及碳纳米管的层数等参数对界面应力的传递均有显著影响。     

SiC换热器材料热物理性质的研究

本文采用ＴＬＰ－１８型激光热常数仪和岛津ＴＭＡ－３０热分析仪研究了温度对等静压ＳｉＣ换热器材料的导热系数和热膨胀系数的影响，并对影响ＳｉＣ抗热震性能的各因素进行了分析。     

Thermal cycling under vacuum and CME evaluation of carbon/epoxy laminates

Dealing with the « French Supersonic Aircraft Research Program», thermal cycling tests in four environments, neutral (vacuum, nitrogen) and oxidative (air, oxygen), were performed on carbon/epoxy cross ply laminates [0₃/90₃]_S. This experimental study was conducted following a local approach through optical and scanning electron microscopy observations and X radiographs and showed a significant effect of the oxygen level on the damage development. Moreover, coefficient of moisture expansion (CME) tests were performed on the same material to characterize the influence of moisture on the sample expansion.     

Measurements of the thermal expansion coefficient of 1Cr18Ni9Ti stainless steel with a laser scanning microdisplacement detection technique

A laser scanning microdisplacement detection system has been developed to measure the thermal expansion coefficient of materials over the range from room temperature to 1200 K. The measurement apparatus consists of a dynamic heating device, a microdisplacement detection system, and a microcomputerbased high-speed data acquisition system. The specimen is dynamically heated from room temperature to 1200 K by passing a large electrical current through it. The thermal expansion of the specimen is detected by the laser detection system, which records the shift of Fraunhofer diffraction fringes with a photodetector. Measurements of the mean linear thermal expansion coefficient of 1Cr18Ni9Ti stainless steel in the range of 300–1200 K are described. The results are compared with other reported values of the thermal expansion coefficient. The maximum deviation between them is about 2.3% at the highest temperature, 1200 K.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

吸湿对印制电路板层压板热膨胀系数的影响

水分对印制电路板的可靠性有重要影响.电路板中的水分子可以改变电路基板的热性能及热力学性能,从而影响电路板及元器件的正常功能.研究了吸湿对两种无卤PCB及两种含卤PCB层压板热膨胀系数的影响,评价了IPC-TM-650 2.4.24测试方法中预处理方法对吸湿样品的适用性.结果表明,PCB层压板中的水分对PCB层压板的热膨胀曲线有明显影响,但传统的热膨胀系数计算方法并不能显示这种影响,对此作了详细分析并提出了改进建议.同时,IPC测试方法中的预处理可以降低湿度对样品热膨胀曲线的影响,但不能完全消除.     

Thermal expansion of glasses in the solid and liquid phases

In this study, the thermal expansion of a number of mixed oxide glasses was measured in the solid and liquid regions by gamma densitometry. Conventional density measurement techniques are limited to either the solid or the liquid phase; however, with this noncontacting technique, the density and thermal expansion of both the solid and the liquid phases may be investigated as the temperature is varied and the glass viscosity varies over a wide range. This technique allows the continuous measurement of density as the liquid cools to a supercooled glass or to a crystalline solid. Lead borate glasses were examined in the range 27 to 42 mol % PbO. The liquid-phase volumetric thermal expansion coefficient was observed to decrease with increasing PbO content, in contrast to the solid-phase linear thermal expansion coefficients. In soda-baria phosphate glasses (50 mol% P₂O₅), liquid-phase volumetric expansion coefficients were found to vary as the solid-phase linear expansion coefficients. Measurements on a lithia-aluminoscilicate glass ceramic were obtained by this method to approximately 400°C above the limit of conventional dilatometry. The gamma densitometry technique can yield density, thermal expansion, glass transition and crystallization information, and quenching-rate dependence data on glasses to temperatures in excess of 1500°C, and thus provides a means for high-temperature characterization of glasses which complements conventional dilatometry, calorimetry, and thermal analysis.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

纤维复合材料的热膨胀系数

提出了一种利用压电光声技术测量材料热膨胀系数的实验方法,并测试了单向复合材料C/C、C/Al的横向、纵向的热膨胀系数。根据已有的理论计算方法与实验结果对该方法的测试结果进行验证,证明了该检测方法的可靠性,进而又测量了C/C、C/Al材料在任一方向上的热膨胀系数。这种方法克服了理论计算过程复杂以及常规手段无法测量任一方向上热膨胀系数的缺陷。     

Measurements of thermal expansion coefficient of phenolic foam at low temperatures

A dilatometer measuring thermal expansion coefficient at low temperatures is introduced. The thermal expansion coefficient of phenolic foam, a widely used thermal insulation material, was measured in the temperature range of 77-293 K by the dilatometer. The results showed that the thermal expansion coefficient of phenolic foam was very low in the tested temperature range with an error of about ±7.3%.     

降低堇青石材料热膨胀系数的途径

堇青石材料热膨胀系数低,是优良的高温抗热震材料,但我国目前生产的堇青石材料热膨胀系数还有待进一步提高.综述了降低堇青石材料热膨胀系数的各种途径,包括调整材料的化学矿物组成、优化制备工艺和后期处理等,指出今后发展的方向是利用负膨胀材料开发低膨胀乃至零膨胀的堇青石材料,以期促进优质堇青石材料的研究与开发.     

微纳晶体材料体膨胀系数测定和计算方法

为解决微纳尺度晶体材料膨胀系数无法直接测量的现状,文章提出一种适用的测试思路及计算方法.该方法基于材料在不同温度下的XRD衍射图谱获得晶胞晶格常数,通过"晶格常数-温度"拟合,计算各个物相晶轴的线膨胀系数,进一步计算获得材料的体膨胀系数.采用该方法对单相高锡焊料及多相PbSn合金焊球进行测试,获取其体膨胀系数,证实方法...     

Creep in Wood Under Variable Climate Conditions: Numerical Modeling and Experimental Validation

This paper deals with the modeling of linear viscoelastic behavior and strain accumulation (accelerated creep) during moisture content changes in timber. A generalized Kelvin–Voigt model is used and associated in series with a shrinkage-swelling element depending on the mechanical and moisture content states of materials. The hygrothermal aging due to climatic variations implies an evolution of rheological parameters depending upon moisture content and temperature. Two distinct viscoelastic laws, one for drying and the other for moistening, are coupled according to the thermodynamic principles when wood is subjected to nonmonotonous moisture variations. An incremental formulation of behavior is established in the finite element program CAST3M (Software developed by C.E.A. (Commissariat á l'Energi Atomique) and an experimental validation from tension creep-recovery tests is presented.     

Characterisation of Thermal Expansion Coefficient of Anisotropic Materials by Electronic Speckle Pattern Interferometry

Abstract:  Carbon fibre composites find wide applications in aerospace, sporting goods industry and biomedicine. Mechanical and thermal properties of such materials are highly anisotropic; therefore, adequate experimental measuring methods are requested to determine them. This paper describes the application of electronic speckle pattern interferometry to full-field, real-time characterisation of the coefficient of thermal expansion (CTE) of anisotropic materials. The topics such as correlation fringes tilt and influence of small rigid body rotation were theoretically described and experimentally verified. A series of measurements was carried out to determine the CTE tensor for unidirectional and bi-directional carbon fibre laminates and to prove the feasibility of the method. The measuring set-up developed includes a temperature control unit for cooling and heating and a one-dimensional in-plane speckle interferometer.     

用热弯实验方法决定导电薄膜的热膨胀系数

研究了热-力载荷下薄膜/基板复合梁的弯曲问题,导出了薄膜的热膨胀系数与试样表面的温度和变形之间的关系式;提出一种测量导电薄膜的热膨胀系数的方法,并用热弯实验测SnO₂膜的热膨胀系数。      

精密技术中热变形误差影响的基本问题

在精密测量和精密机械等精密工程技术领域，影响精度的众多因素中，温度变化引起的热变形误差已成为主要的甚至决定因素、由于精度不断提高，传统热变形误差的某些概念与方法已失去实用价值．该文分析了热变形误差的研究与应用现状，研究了适应高精度技术的热变形误差新概念、新方法，提出了几种实用性不同的热膨胀系数概念以及精确热膨胀系数和科学热膨胀系数定义．在全面分析热变形误差的多种因素基础上，研究了物体形状结构对其参数热变形影响的新认识并举例说明，同时提出相应的热变形系数，最后简介了考虑形状影响的热变形误差建模方法．     

Thermal expansion behavior and microstructure in bulk nanocrystalline selenium by thermomechanical analysis

Thermal expansion behavior of bulk nanocrystalline (NC) Se samples with a grain size range of 16–46 nm was studied by thermomechanical analysis (TMA) in the temperature range 290–373 K. Bulk NC Se samples were prepared by isothermally crystallizing the as-quenched bulk amorphous solid at 373–478 K. The glass transition and crystallization of the remaining amorphous Se in the partially crystallized samples were studied by TMA, and compared with the results of differential scanning calorimetry (DSC). The glass transition temperature, as determined from the thermal expansion behavior, was 308 K, 11 K lower than the value by DSC analysis. A structural densification phenomenon was observed in a grain growth process of an as-crystallized NC Se sample by TMA. It was found that the linear thermal expansion coefficient of the bulk NC Se sample increased with a reduction of grain size, from which the deduced thermal expansion coefficient of the interface decreased with the refinement of the grain size.     

铜线材热膨胀系数的理论分析和实验研究

分析了面心立方结构晶体铜线材的热膨胀系数随温度的变化关系。采用精密仪器DIL402PC热膨胀仪测定了铜的热膨胀系数,得到在100℃到380℃之间铜的热膨胀系数基本保持在2.0836×10^-5/℃,比通常实验室条件下测得的结果稍大。温度大于380℃时,铜的热膨胀系数随温度呈线性增加。理论分析与实验测定的结果基本一致,说明应用此理论亦可以解释其它面心结构晶体的热膨胀系数。     

TMA4000在电子工业领域中使用标准测试方法的应用

电子线路板的主要破坏原因之一是由热膨胀引起的问题。要防止这种情况发生,电子工程师采用热导体来发散热量,用低膨胀性材料来配合低膨胀率的硅片和陶瓷绝缘体的使用。热机械分析（TMA）长期以来应用于测量线路板、电子元件和组成材料（CTE）。针对玻璃化转变温度、热膨胀系数变化的点、样品软化和应力释放效应的发生,已经建立起成熟可靠的标准测试方法。对于层状复合产品,TMA相应的测试方法可以确定在评估升温过程中材料的分层所需时阃。TMA4000的设计大大简化了上述测试过程,非常适用于测量低膨胀率的小器件的膨胀。本应用文章提供了这些标准方法的一些案例。     

Physical and Thermal Properties of P2O5-Al2O3-BaO-La2O3 Glasses

The physical and thermal properties of P2O5-Al2O3-BaO-La2O3 glasses were investigated. The effects of glass compositions on the transition temperature, thermal expansion coefficient, density, hardness and refractive index of glasses were studied. The highest hardness of the glasses is 4143.891 MPa and the lowest thermal expansion coefficient of the glasses is 71.770×10-7/℃. A phosphate glass with high mechanical strength and good thermal characteristic is obtained.