Thermomechanical analysis apparatus

Dynamic properties are more relevant than the more usual quasi-static stress-strain tests for any application where the dynamic response is important. For example, the dynamic modulus at low strain may not undergo the same proportionate change as the quasi-static tensile modulus. Dynamic properties are not measured as frequently as they should be simply because of high apparatus costs. However, the introduction of dynamic thermomechanical analysis (DMTA) has greatly widened the availability of dynamic property measurement. 

The three resins above were tested by thermomechanical analysis (TMA) on a Met-tler 40 apparatus. Triplicate samples of beech wood alone, and of two beech wood plys each 0.6 mm thick bonded with each resin system were tested. Sample dimensions were 21 mm x 6 mm x 1.2 mm. The samples were tested in non-isothermal mode from 40°C to 220°C at heating rates of 10°C/min, 20°C/min and 40°C/min with a Mettler 40 TMA apparatus in three-point bending on a span of 18 mm. A continuous force cycling between 0.1 N and 0.5 N and back to 0.1 N was applied on the specimens with each force cycle duration being 12 s. The classical mechanics relation between force and deflection E = [L /(4bh )][AF/(Af)] (where L is the sample length, AF the force variation applied and A/ the resulting deflection, b the width and h the thickness of the sample) allows calculation of the modulus of elasticity E for each case tested and to follow its rise as functions of both temperature and time. The deflections A/ obtained and the values of E obtained from them proved to be constant and reproducible. 

The resins were tested dynamically by thermomechanical analysis (TMA) on a Met-tler 40 apparatus. Triplicate samples of beech wood alone, and of two beech wood... 

The experimental procedures for the determination of and are different. One can measure in a thermomechanical analysis (TMA) apparatus and then calculate from it. Or, one can determine directly by using an apparatus which produces fitll P-V-T data, that is specific volume v as a function of temperature T, v(T), plus (T) plus also isothermal compressibility. /T), where... 

Thermomechanical analysis (TMA) is a technique that measures the deformation of a substance under non-oscillatory load or strain as a function of temperature or time. Thermo-dilatometry (see Section 2.2.4) is a technique that measures dimensional changes of a sample as a function of temperature or time. Both of these techniques can be applied using the same apparatus. The sample is heated or cooled at a certain rate, or is maintained isothermally at a fixed temperature. 

Evaluation of the necessary characteristic parameters in equation 27a proceeds as follows. One can use the thermomechanical analysis (TMA) in the expansion mode and determine at the atmospheric pressure, the dependence of specific volume V on temperature T. By fitting the experimental results to equation 27b one obtains the characteristic parameters v and T. If one performs full P-V-T determination [this can be done with the so-called Gnomix apparatus (59) used also by us to advantage (60)], then one represents experimental results by equation 27a and finds by a least-squares procedure the parameters P, v, and T. ... 

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