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Elastic modulus anisotropy

Since the increase of the elastic modulus of oriented polymers with draw ratio is, to a large extent, the consequence of the tie molecules or intercrystalline bridges interconnecting crystal blocks within the fibrils 72) one may anticipate a correlation to exist between indentation anisotropy and modulus. Recent data 23) illustrating the... [Pg.143]

Fig. 24. Correlation of microindentation anisotropy and elastic modulus for die-drawn PE and... Fig. 24. Correlation of microindentation anisotropy and elastic modulus for die-drawn PE and...
In this equation, 8 is the dielectric anisotropy, K - (K +K j)/ is an average splay-bend elastic modulus, and E is the applied electric field. In this presentation, the curve must be linear when the Rapini approximation for the... [Pg.167]

Figure 4. Calculated properties vs. temperature and anisotropy coefficient (p) elastic modulus, MPa, along Y/Z-axes (a) and its relative difference, %, to X-axis (b) thermal conductivity, W/mK, along Y/Z-axes (c) and its relative difference, %, to X-axis (d). Figure 4. Calculated properties vs. temperature and anisotropy coefficient (p) elastic modulus, MPa, along Y/Z-axes (a) and its relative difference, %, to X-axis (b) thermal conductivity, W/mK, along Y/Z-axes (c) and its relative difference, %, to X-axis (d).
Anisotropy. Since the distances between atoms or molecules, as well as the bond strengths between them, varies with direction (with respect to the axes of the unit cell), physical properties of a crystal may vary with direction. This is called anisotropy (cf. Section 9.1). For instance, the elastic modulus or the breaking strength of a crystal may depend on the direction of the force. Anisotropy tends to be more pronounced for crystal lattices in which the unit cell is more asymmetric. [Pg.606]

In Sect. 3.2 the preparation of magnetic polymer composites under uniform magnetic field has been described. The resulting composites show anisotropic behavior. The anisotropy manifests itself in the direction-dependent elastic modulus. Figure 13 shows carbonyl iron-loaded mPDMS elastomers. All three samples contain the same amount of filler particles, but the spatial distribution of the filler is different, as shown in the figure. [Pg.155]

The experimental data were analyzed on the basis of Eq. 7. It is seen that the slopes of the straight lines (elastic moduli, G) are direction-dependent. The elastic modulus is larger if the compression force and the direction of pearl chain structure are parallel. This finding indicates a strong mechanical anisotropy. It can be concluded that the spatial distribution of the solid particles has a decisive effect on the stress-strain dependence. [Pg.155]

The heterogeneity of the crystalline polymer solid is accentuated still more in the case of mechanical properties by the enormous mechanical anisotropy of the crystals and the large difference in the elastic moduli of the crystalline and amorphous components. With polyethylene, the elastic modulus of the crystals is 3452 or 2403 X 1010 dynes/cm2 in the chain direction (E ) and 4 X 1010 dynes/cm2 in the lateral direction (E ) (2, 3). The elastic modulus of the amorphous component (Ea) of polyethylene is 109-1010 dynes/cm2 (4). This is significantly less than Eu and Ebut at least 10 times the elastic modulus of a rubber that has about five monomers in the chain segments between the crosslinks. This is quite surprising since room temperature is far above the glass transition temperature of polyethylene (Tg is either —20°C or — 120°C), and therefore one would expect a fully developed rubbery... [Pg.17]

All physical parameters mentioned above are material specific and temperature dependent (for a detailed discussion of the material properties of nematics, see for instance [4]). Nevertheless, some general trends are characteristic for most nematics. With the increase of temperature the absolute values of the anisotropies usually decrease, until they drop to zero at the nematic-isotropic phase transition. The viscosity coefficients decrease with increasing temperature as well, while the electrical conductivities increase. If the substance has a smectic phase at lower temperatures, some pre-transitional effects may be expected already in the nematic phase. One example has already been mentioned when discussing the sign of Ua- Another example is the divergence of the elastic modulus K2 close to the nematic-smecticA transition since the incipient smectic structure with an orientation of the layers perpendicular to n impedes twist deformations. [Pg.61]

Highly drawn fibres and films exhibit an almost complete orientation of the crystal lattice, a high orientation of the amorphous component and a fairly good orientation of lamellae either perpendicular or at a finite angle to the fibre axis. The same anisotropy applies to mechanical properties with a high elastic modulus in the fibre axis and a smaller one perpendicular to Technically the most important feature is... [Pg.48]

It is clear from the analysis shown in Figure 25, Figure 26 and Figure 27 that the trends of ratio of static elastic modulus versus ratio of dynamic elastic modulus for POP specimens and POP-cement mix specimen are always below the line of comparison. This indicates that the anisotropy of the specimen is influencing the dynamic elastic modulus more than the static elastic modulus. The low strain experiments on the POP and POP-cement mix models also indicate that the effect of joints is more predominant for the sample material of higher strength than the lower strength material. [Pg.131]

The rocks with planar anisotropy exhibit the highest strength in the direction perpendicular to the anisotropy and the lowest at an inclination of 30°-45° with the plane of anisotropy in jointed samples. The anisotropy of the specimen influences the dynamic elastic modulus more than the static elastic modulus... [Pg.132]

The anisotropy of the specimen is influencing the d5mamic elastic modulus more than the static elastic modulus. [Pg.132]

In this paper the compressive strength/elastic modulus of the jointed rock mass was estimated as a function of intact rock strength/modulus and joint factor. The joint factor reflects the combined effect of joint frequency, joint inclination and joint strength. Therefore, having known the intact rock properties and the joint factor, jointed rock properties can be estimated. The test results indicated that the rock mass strength decreases with an increase in the joint frequency and a sharp transition was observed from brittle to ductile behaviour with an increase in the number of joints. It was also found that the rocks with planar anisotropy exhibit the highest strength in the direction perpendicular to the anisotropy and the lowest at an inclination of 30o-45o in jointed samples. The anisotropy of the specimen influences the dynamic elastic modulus more than the static elastic modulus. The results were also compared well with the published works of different authors for different type of rocks. [Pg.286]

In order to effectively assess the variation of the directionally dependent elastic modulus, the results were normalised relative to elastic modulus along Y direction, i.e. = Ej/E2 (i=l, 2 and 3), as shown in Figure 11. The comparison and difference can be more readily seen with normalised average values added. The degree of anisotropy (DA) is thus be calculated and plotted for each sintering temperature DA=l-smallest normalised modulus, with DA=0 when fliUy isotropic and DA=1, fully anisotropic. [Pg.123]

Internal-friction anisotropy varied from about 3 to 20. Internal friction was always higher in the transverse direction, which tends to sample the matrix. Despite their wide elastic-modulus-anisotropy variation, the graphite-reinforced epoxies varied little in internal-friction anisotropy. [Pg.275]

One can see firom Table n that the conditions of polymers preparation essentially influence their thermal and mechanical properties. The data of Table II show an evident anisotropy of the properties of polymer aligned in the magnetic field. First of all, noteworthy is the high value of elasticity modulus for the aligned polymer in the direction perpendicular to the direction of the magnetic field. It is about four times... [Pg.384]


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See also in sourсe #XX -- [ Pg.284 ]




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