Performance test methods mechanical properties

Much of the experimental work in chemistry deals with predicting or inferring properties of objects from measurements that are only indirectly related to the properties. For example, spectroscopic methods do not provide a measure of molecular stmcture directly, but, rather, indirecdy as a result of the effect of the relative location of atoms on the electronic environment in the molecule. That is, stmctural information is inferred from frequency shifts, band intensities, and fine stmcture. Many other types of properties are also studied by this indirect observation, eg, reactivity, elasticity, and permeabiHty, for which a priori theoretical models are unknown, imperfect, or too compHcated for practical use. Also, it is often desirable to predict a property even though that property is actually measurable. Examples are predicting the performance of a mechanical part by means of nondestmctive testing (qv) methods and predicting the biological activity of a pharmaceutical before it is synthesized. 

Evaluating composite performance requires test methods for mechanical properties of the constituent materials (fibers, tows, filaments, and matrices) as well as the composite materials themselves. The types and quantities of tests to be performed, and the selection of testing parameters, depends on the information desired. For material development, the tests may be much simpler and less numerous than those that would be chosen for design qualification, but may encompass a greater range of test parameters than would be expected in service. In the case of materials development, it is the trends in the data and the mechanisms by which failures occur which are most important, and it is crucial to examine the extremes of behavior. For component design and qualification, it is more important to know the reliability and reproducibility of the material under conditions which resemble the expected service conditions. 

Table 12.18 provides a list of standard test methods for the evaluation of solvent and chemical susceptibilities of polymers and their blends. These tests are to help in (1) designing of fabricated parts, (2) comparison of different materials and (3) characterization of materials for long term performance, etc. The materials performance, summarized after the immersion in reagents for 7 days at elevated temperatures according to ASTM D 543, based on changes in weight, dimensions, appearance and mechanical properties, is shown in Table 12.19. 

In this work, DC electric field-assisted ion exchange was carried out to enhance the sodium-potassium inter-diffusion and improve the mechanical performance of borosilicafe glass. Elecfric fields with intensity varying between 100 V cm and 3000 V cm were applied in both direct and inverted polarizations. Four point bending test and the Vickers indentation method were used to characterize the mechanical properties. Energy dispersion x-ray spectroscopy was carried out to determine the potassium concentration within the surface layers of the samples. 

External factors that will influence polymer mechanical properties are temperature or thermal treatment, temperature history, large differences in pressure, and environmental factors such as humidity, solar radiation, or other types of radiation. The mechanical properties of polymer are also sensitive to the methods and variables used for testing, such as strain deformation as well as the rate at which the strain is performed. Finally, the mechanical behavior of polymeric materials and the values of their mechanical properties will be sensitive to the kind of strain that is imposed by the applied force, namely, tension, compression, biaxial, or shear. 

Tranj-laminar fracture of composites with a certain amount of fibres in the throughthickness direction will lead to fibre breaking with significant effects on delamination resistance (see e.g. Refs [24,37] for details). Woven fibre mats, 3D fibre performs or additional 3D reinforcement (pins and stitching) of FRP composites with fibres ahgned in one plane (see e.g. Refs [84,85]) have been developed and can be tested for their fracture mechanics properties. The typical approach for testing these is to apply a standard test method developed for unidirectionally reinforced FRP composites and to assess the difference in delamination resistance compared to the standard laminate. So far, that approach has yielded (nominal) numbers, but their interpretation is not... 

The mechanical properties of concrete evaluated were the compressive and tensile strengths, at 7 and 28 days. Each result represents an average of 3 specimens. The compressive strength tests where performed according to the NP EN 12390-3 [16], where as the tensile strength test adopted was the Brazilian method, according to NBR 7222 [17], which determines the tensile strength by diametrical compression of specimens. 

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