Testing methods thermomechanical

ASTM E 1545-00, ASTM Book of Standards 2002. Standard Test Method for Assignment of the Glass Transition Temperature by Thermomechanical Analysis . ASTM International, Conshohocken, PA. 

ASTM E831, 2003. Standard test method for linear thermal expansion of solid materials by thermomechanical analysis. 

While TMA is one of the older and simpler forms of thermal analysis, its importance is in no way diminished by its age. Advances in DSC technology and the appearance of dynamic mechanical analysis (DMA) as a common analytical tool have decreased the use of it for measuring glass transitions, but nothing else allows the measurement of CTE as readily as TMA. In addition, the ability to run standardized material test methods at elevated temperatures easily makes TMA a reasonable alternative to larger mechanical testers. As the electronic, biomedical, and aerospace industries continue to push the operating limits of polymers and their composites, this information will become even more important. During the last 5 years a major renewed interest in dilatometry and volumetric expansion has been seen. Other thermomechanical techniques will also likely be developed or modernized as new problems arise. 

There are currently no standards tests for measuring the thermal expansion of plastics in ISO or in BS 2782. In ASTM, test method D696 [124] uses a relatively thick test piece, which is placed in a chamber whose temperature can be controlled. This is shown schematically in Fig. 23. The expansion of the sample is transmitted to a remote dial gauge via a quartz rod that has a very low expansion coefficient. This same technique is applied in modern thermomechanical analyzers (TMA). but the dial gauge is replaced by linear displacement transducers or other electronic devices capable of detecting smaller dimensional changes. In turn this allows thinner specimens to be tested and permits wider temperature ranges to be examined. There are developments wnthin the ISO to provide a standard for these types of instruments. 

E 1782 (1998) Vapour pressure by DSC/DTA E 1824 (1996) Standard Test Method for Assignment of a Glass Transition Temperature using Thermomechanical Analysis under Tension... 

Standard Test Method for Distortion Temperature in Three-Point Bending by Thermomechanical Analysis... 

The reliability of electronic systems depends on extensive testing, inspection, and evaluation of all parts of the design and manufacturing process, including the adhesives used in the systems. Test methods for adhesives and adhesive-bonded assemblies may be generally classified as physical, electrical, environmental, thermal, mechanical or thermomechanical, and chemical (Table 7.1). This chapter summarizes most of the methods used to test and evaluate adhesives used in electronics. It is not intended to provide detailed instructions, but to lead the reader to the appropriate government or industry specifications, documents that are available from the various organizations listed in Table 7.2. 

Thermomechanical-analysis (TMA) testing is used to measure a material s expansion coefficient above and below the glass-transition temperature or Tg. Thermomechanical analysis continuously monitors the expansion of a probe on a sample as a function of temperature. The standard test method for TMA is ASTM D3386, Coefficient of Linear Thermal Expansion of Electrical Insulating Materials.In addition to the glass-transition temperature or Tg, the expansion coefficients above and below Tg are reported. 

Frequency Dependencies in Transition Studies. The choice of a testing frequency or its effect on the resulting data must be addressed. A short discussion of how frequencies are chosen and how they affect the measurement of transitions is in order. Considering that higher frequencies induce more elasticlike behavior, there is some concern that a material will act stiffer than it really is if the test frequency is chosen to be too high. Frequencies for testing are normally chosen by one of three methods. The most scientific method would be to use the frequency of the stress or strain that the material is exposed to in the real world. However, this is often outside of the range of the available instrumentation. In some cases, the test method or the industry standard sets a certain frequency and this frequency is used. Ideally a standard method like this is chosen so that the data collected on various commercial instruments can be shown to be compatible. Some of the ASTM methods for TMA (thermomechanical analysis) and DMA are listed in Table 1. Many industries have their own standards so it is important to... 

A temperature calibration procedure for TMA has been proposed (53-55) and subsequently included as an ASTM method (Test Method for Temperature Calibration of Thermomechanical Analyzers, E1363-90). It uses a penetration probe and the melting temperature of one or more standard materials. Pure metals with sharp melting points are the standards often used. An open DSC pan may be used to contain the calibrant material. Another potential material would be the selected shape memory alloy, reported to be reproducible to 1°C (56). Several reviews on temperature calibration for TMA have been published based on ASTM efforts in this area (54,55). Sircar (26) suggests that, when used for elastomer evaluation, temperature calibration for TMA should be conducted with low melting liquids as in DSC. For calibration of the expansion, one manufacturer s manual (TA Instruments) recommends aluminum for calibrating the linear expansion parameter. Other calibration standards suggested for the linear coefficient of thermal expansion (CTE) are lead (57) and copper (58). 

E1363, Test Method for Temperature Calibration of Thermomechanical Analyzers... 

E2092, Standard Test Method for Distortion Temperature in Three-Point Bending by Thermomechanical Analysis D3418, Transition Temperature of Polymers by Thertnal Analysis STP23594S, The Use of Thermomechanical Analysis as a Viable Alternative for the Determination of the Tensile Heat Distortion Temperature of Polymer Films... 

Because there is no precedent for using ceramic composites in a nuclear reactor, standard test procedures will be established to qualify ceramic composites for nuclear reactor applications. In order to use SiCf/SiC in applications of structural components, it is necessary for well-established testing standards and material codes to be in place. CMCs have different mechanical behaviors than those of organic matrix composites and monolithic ceramics. Thus, new test methods are required. Some standards for the thermomechanical properties of CMCs already exist, as summarized in Table 12.9. 

ISO/DIS 12111 Metallic materials—Fatigue testing—Strain-controlled thermomechanical fatigue testing method... 

ASTM E831, Standard Test Method for Linear Thermal Expansion of Solid Materials by Thermomechanical Analysis For thermal expansion coefficient measurement. 

Finally, there is the extremely important group of relaxation methods for determining T. These can be based on either mechanical (sometimes thermomechanical) or electrical relaxations occurring within the material, and, although they do not always give results that are completely consistent with those obtained by the static mechanical tests already mentioned, they are considered very reliable and are widely used. 

CHARACTERIZATION. Melting points were determined on an E. I. DuPont Series 99 Thermal Analyzer at 20°C/min. Inherent viscosities of polyamic acid solutions were obtained at a concentration of 0.5% (w/w) in DMAc at 35°C. Glass transition temperatures (T ) of the fully cured polymer films were measured by thermomechanical analysis (TMA) on a DuPont 943 Analyzer in air at 5°C/min. Films fully-cured at 300°C were tested for solubility at 3-5% (w/w) solids concentration in DMAc,N,N-dimethylformamide (DMF), and chloroform (CHCl-j). Solubilities at room temperature were noted after periods of 3 hours, 1 day and 5 days. Refractive indices of 1 mil thick films were obtained at ambient temperature by the Becke line method (11) using a polarizing microscope and standard immersion liquids obtained from R. P. Cargille Labs. 

Thermomechanical analysis methods are used in geometries more commonly associated with traditional mechanical testing to increase sensitivity or to mimic other tests. The most common of these are the flexural and penetration modes. Flexure studies involve loading a thin beam, often a splinter of material, with a constant load of lOOmN or more and heating until... 

In the present work, the graded layer properties of the thermal stress relaxation type functionally gradient material TiC-NiyAl were investigated. First, the thermomechanical properties of the each layer of the composite was tested. Second, the microstructure of the composite was examined. Next, the interface residual thermal stress of TiC-NiaAl sphere in the sintering process was calculated by the analysis method. Then, the relationship between the stress and the thickness of NisAl was also presented. Finally, the effect of the residual thermal stress on the properties of TiC-NiaAl composite was discussed. 

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