Elastic elongation

Elastomers are defined as polymers that can be repeatedly stretched to 200% elastic elongation and will return to their original length when released. They can... 

Most metals and ceramics have elastic elongation of less than 2%. Stretching in these materials involves the movement of atoms. In contrast, polymers can be easily elongated because the applied stress promotes linear formation of the polymer backbone. 

Elastic Elongation. The elasticity as measured by the extent of reversible elongation. 

Up to point 1 in the curve the sample experiences an elastic elongation i.e. when the stress is removed, the material returns to its original shape. Consequently the E-modulus is a measure for the elasticity and rigidity of a material. 

Three important properties can be inferred from the tensile test i.e. elastic limit (i.e. the point of maximum elastic elongation), tensile strength and E-modulus. In many cases the transition point between the elastic and plastic deformation is not visible in the graph. For that reason it has been determined that this point is situated at an value of 0.002 and the accompanying tensile stress is determined as represented in figure 10.9. 

After leaving the die, the extruded strand shows an instantaneous increase in thickness. This is a consequence of the elastic elongation, in particular induced by the elongational flow in the die, which spontaneously recovers when the material leaves the die. This so-called die swell or extrudate swell has to be taken into account when designing the die in particular, when the cross-section of the extrudate is not circular, not only a diameter increase but also a distortion in shape occurs. The distortion can be prevented by adjusting the shape of the die opening. 

Elastic elongation—The reversible change in length of a material when it is stretched and the stretching force is then removed. 

Within the elastic portion of the stress-strain curve, when an applied stress is removed, the deformation it produced disappears, and the material returns to its original dimensions. We define the elastic limit diS the last point on the stress-strain curve at which this is true. Similarly, the elastic elongation is defined as the maximum strain under which elastic behavior is maintained thus the elastic elongation is the strain corresponding to the stress at the elastic limit. Values of elongation are typically reported in percent. 

Sample identifi- cation Resin Fiber volume, % Void volume, % Corrected outer fiber ultimate stress Modulus of elasticity Elongation, %... 

Now, we will translate the basic equation (3) into elastomechanics. Looking into the translation table we have to substitute the weight P by the corresponding Hooke-factors, which describes the relationship between bar-forces Sj, cross-sections of bars F, elasticity Ei, elastic elongations v,- and lengths /, (with / , = F, Ei)... 

Both equations may also interpreted as describing the equilibrium in each node the distances in space I -f v) between adjacent nodes are just such, that the forces s created by the elastical elongations x are with respect to amount and direction in space in equilibrium at each and every node. 

The beam-bending method was describes by Jones [11] and Hagy [12] and is now an ASTM standard [13]. A schematic drawing of the experimental arrangement is shown in Fig. 5b, where a specimen of length L and inertia I is symmetrically bent under a weight P. From elasticity theory, the elastic elongation is. 

Elastic elongation is determined by the extent of reversible elongation. For flexible plastics , it corresponds only to the first part of the plot. 

TABLE 52.6. Variation in the tensile strength, modulus of elasticity, elongation, and some electrical properties with irradiation dose in polypropylenes. 

Pol3mier type Elastic elongation, % Total elongation, Yield Z strength, MPa Tensile strength, MPa Tensile modulus, GPa... 

Keywords bulk continuous fibers (BCF), crystallinity, drawing, elasticity, elongation, fiber-forming polymer, fiber monofilament, low oriented yam (LOY), melt blown process, melting, monofilament, multifilament silk, orientation, partially oriented yam (POY), staple fibers, spinning, spunbonded fibers, stmcture, technical fiber, tenacity, textile fiber, texturing. 

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