Tensile Modulus of elasticity

Stiffness of the films and sheeting can be measured as the tensile modulus of elasticity. Droop or drape tests may be used, particularly for multilayer products. The stiffness is strongly influenced by thickness (to the third power) and temperature, and is important to the processing of film in printing, coating, or end use appHcations where it affects the "hand" of the product. 

The constant G, called the shear modulus, the modulus of rigidity, or the torsion modulus, is directly comparable to the modulus of elasticity used in direct-stress applications. Only two material constants are required to characterize a material if one assumes the material to be linearly elastic, homogeneous, and isotropic. However, three material constants exist the tensile modulus of elasticity (E), Poisson s ratio (v), and the shear modulus (G). An equation relating these three constants, based on engineering s elasticity principles, follows ... 

Although hardness is a somewhat nebulous term, it can be defined in terms of the tensile modulus of elasticity. From a more practical side, it is usually characterized by a combination of three measurable parameters (1) scratch resistance (2) abrasion or mar resistance and (3) indentation under load. To measure scratch resistance or hardness, an approach is where a specimen is moved laterally under a loaded diamond point. The hardness value is expressed as the load divided by the width of the scratch. In other tests, especially in the paint industry, the surface is scratched with lead pencils of different hardnesses. The hardness of the surface is defined by the pencil hardness that first causes a visible scratch. Other tests include a sand-blast spray evaluation. 

Over the six-week period of permeation testing, sample containers from each type and temperature set were randomly selected and used for tensile testing. The tensile specimens were prepared and tested following the procedures of ASTM Test Method D1708-79 with the following modifications (i) the bottles were drained, and five specimens were cut parallel to the long axis of the cylinder (machine direction), (ii) the specimens were tested immediately after blotting to remove any surface solvent, (iii) a test speed of 5.08 cm/min. (2 in./min.) was used, and (iv) the tensile modulus of elasticity was calculated from the initial slope of the load-extension curve. 

Calculations of tensile strength and tensile modulus of elasticity are described in the text above. 

The procedure is illustrated in the description of the ASTM method using test results for six materials (realistically round average figures for tensile strength at break and tensile modulus of elasticity are given here) ... 

For the majority of plastics (within the same group) the tensile modulus of elasticity increases approximately linearly with the degree of crystallinity [5], The data for linear and branched polymers follow the same approximate relationship. It is not clear whether the same molecular principles is applicable to WPCs (Table 8.13), but their tensile modulus of elasticity vary between different brands quite significantly. 

Temperature coefficient, 205, 206, 335, 495, 506, 509, 511, 512 Temperature factor, 303 Temperature, effect on viscosity, 633 Tensile modulus of elasticity of composite materials, 329... 

Material Form and condition Yield strength (0.2% offset) Ultimate strength cr (MNm- ) Tensile modulus of elasticity (Nm-2)... 

Many RPs and URPs have a definite tensile modulus of elasticity (E) where deformation is directly proportional to their loads below the proportional limits. Since stress is proportional to load and strain to... 

As an example, Fig. 86 shows the tensile modulus of elasticity E vs temperature T plots, as measured for the 83PU-17PHEMA network and ND-containing composites based thereon (their CR spectra were described in Sects. 3.2 and 3.8). One can see a considerable and various (by a sign and magnitude) influence of small ND additives on the elastic properties of polymer matrix additionally, these changes are different in the different temperature regions. 

Although hardness is a somewhat nebulous term, it can be defined in terms of the tensile modulus of elasticity. From a more practical side, it is usually characterized by a combination of three measurable parameters 1) scratch resistance 2) abrasion or mar resistance 3) indentation under load (see Table 3-23). 

Figure 6-37. The relationship of different reinforcing fibers used in composites, comparing their specific tensile strength and their specific tensile modulus of elasticity (the specific value = the mechanical property divided by the specific gravity).

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