Elastic modulus, in compressive

Figure 8.57 Elastic modulus in compression vs. temperature for DuPont Hytrel thermoplastic polyester elastomer resins [7].

Density, g/cm Elastic modulus (in compression), E, GPa Fracture toughness, itic, MPa m Strength ... 

In respect of the classical mechanics, E is an "ideal" coefficient, like the elasticity modulus in Hooke s model. Most of the practical compressions/dilatation experiments carried out with adsorption layers are comparable to the screening of elastic properties in material science. In analogy to the coefficients of the 3D-elasticity theory, we have to consider complex coefficients in surface rheology. The surface elasticity coefficient written as a complex modulus therefore has the form... 

On the other hand, the mechanical properties of monolithic carbon gels are of importance when they are to be used as adsorbents and catalyst supports in fixed-bed reactors, since they must resist the weight of the bed and the stress produced by its vibrations or movements. A few smdies have been published on the mechanical properties of resorcinol-formaldehyde carbon gels under compression [7,36,37]. The compressive stress-strain curves of carbon aerogels are typical of brittle materials. The elastic modulus and compressive strength depend largely on the network connectivity and therefore on the bulk density, which in turn depends on the porosity, mainly the meso- and macroporosity. These mechanical properties show a power-law density dependence with an exponent close to 2, which is typical of open-cell foams. 

The elastic modulus, in contrast to compressive strength, does not noticeably increase with curing time, as it has been found by Croney and Croney (1991) testing specimens produced with crushed aggregates or gravels and cured for up to 520 and 104 weeks, respectively. Moreover, Croney and Croney (1991) state that the computed stresses in the concrete slab are not very sensitive to small changes in the elastic modulus. 

It should be noted that the elastic modulus in bending is not necessarily the same as that in tension or compression. It may be determined analytically or by physical test. If it is determined by test it should be ensured that the test span is sufficiently large that deflection due to shear is negligible. The shear rigidity of a section may be defined as the product of shear modulus and the cross section of the shear area. 

Figure 3.12. The dependence of the elasticity modulus with compressing compr. d) and diffusion coefficient D of acetone (2) on conversion degree in the polymerization of TGM-3. Conditions of polymerization are presented in Tables 3.2 and 3.3.

In a recent study from Li Chen et al. [66], a chitosan-multiwalled carbon nanotube/ hydroxyapatite nanocomposite exhibited excellent mechanical properties, good bioactivity, and biocompadbility. The mechanical properties of the composites were evaluated by measuring their compressive strength and elastic modulus. The elastic modulus and compressive strength increased sharply from 509.9 to 1089.1 MPa and from 33.2 to 105.5 MPa with an increase of multiwalled carbon/chitosan weight ratios from 0% to 5%, respectively. The cell biocompatibility of the composites was tested in vitro and showed good results. 

The value of the elastic modulus in bending, which is taken as the effective average of the tensile and compressive moduli (usually measured directly), is a function of the loading rate and time as are the... 

Figure 17.7 (a) Field-dependent magnetization of CoFe O -BC shows increase in saturation magnetization with increase in total concentration of Fe and Co + ions in the precursor, (b) Stress Vs strain curve obtained under compression shows higher elastic modtdus for magnetic nanopaper, whereas lower elastic modulus in the case of magnetic aerogel. 

The relation adduced in Figure 5.15 between the probability of the formation of frame bonds T and the spectral dimension d assumes a certain correlation d and the mechanical properties of epoxy polymers, particularly the elasticity modulus. In Figure 6.5 the dependence of the elasticity modulus E at compression on the value d is adduced, which confirms this supposition. According to the data of Figure 6.5 the greatest value of E for the studied epoxy polymers can be estimated, which is equal to 5 GPa at the maximum value d = 1.73 [31]. 

All AFM meastuements were carried out in phosphate buffer solution (PBS). To fit the elastic modulus, the compression region of the approach portion of the force-distance curve was fit to eqn [13] ... 

Fig. 4. The immediate effect of temperature on the modulus of elasticity of clear wood, relative to the value at 20°C. The plot is a composite of studies on the modulus as measured in hen ding, in tension parallel to grain, and in compression parallel to grain. VariabiUty in reported results is illustrated by the...

The high elastic modulus, compressive strength, and wear resistance of cemented carbides make them ideal candidates for use in boring bars, long shafts, and plungers, where reduction in deflection, chatter, and vibration are concerns. Metal, ceramic, and carbide powder-compacting dies and punches are generahy made of 6 wt % and 11 wt % Co ahoys, respectively. Another apphcation area for carbides is the synthetic diamond industry where carbides are used for dies and pistons (see Carbon). 

Armor. Sihcon carbide is used as a candidate in composite armor protection systems. Its high hardness, compressive strength, and elastic modulus provide superior baUistic capabihty to defeat high velocity projectile threats. In addition, its low specific density makes it suitable for apphcations where weight requirements are critical (11). 

Hertz [27] solved the problem of the contact between two elastic elliptical bodies by modeling each body as an infinite half plane which is loaded over a contact area that is small in comparison to the body itself. The requirement of small areas of contact further allowed Hertz to use a parabola to represent the shape of the profile of the ellipses. In essence. Hertz modeled the interaction of elliptical asperities in contact. Fundamental in his solution is the assumption that, when two elliptical objects are compressed against one another, the shape of the deformed mating surface lies between the shape of the two undeformed surfaces but more closely resembles the shape of the surface with the higher elastic modulus. This means the deformed shape after two spheres are pressed against one another is a spherical shape. 

The test can provide compressive stress, compressive yield, and modulus. Many plastics do not show a true compressive modulus of elasticity. When loaded in compression, they display a deformation, but show almost no elastic portion on a stress-strain curve those types of materials should be compressed with light loads. The data are derived in the same manner as in the tensile test. Compression test specimen usually requires careful edge loading of the test specimens otherwise the edges tend to flour/spread out resulting in inacturate test result readings (2-19). 

---