Tensile stress-strain response

FIGURE 11.18 Tensile stress-strain responses of polypropylene/styrene-butadiene rubber (PP-SBR) blends at several ratios (where LL is linear low molecular weight LH is linear high molecular weight BL is branched low molecular weight and BH is branched high molecular weight). (From Cook, R.F., Koester, K.J., Macosko, C.W., and Ajbani, M., Polym. Eng. Sci., 45, 1487, 2005.)... 

The tensile stress-strain response of the homopolymer, and of two rubber modified grades of polystyrene, is shown in Fig. 1. The principal mode of deformation is crazing and all three materials exhibit a craze yield stress. However, there is no evidence of localized necking in any of the three materials. The craze yield stress decreases and the elongation to fracture, and the toughness, increase significantly with increase in rubber content. 

Fig. 26a-d. Tensile stress-strain response at 20 °C and at a strain rate of 1.3x 10 s" of a) reconstituted sample containing 15% large particles b) 5% large particles c) 15% small particles d) 5% small particles... 

Fig. 7.22 The computed tensile-stress-strain response of Pd4oNi4oP2o glass at 564 K for four tensile-strain rates compared with experimental stress-strain curves of de Hey et al. (1998) shown in the inset, = 1319 MPa.

Vaidya, R. U., Butt, D. P., Hersman, L. E., and Zurek, A. K., "Effect of Microbiologically Influenced Corrosion on the Tensile Stress-Strain Response of Aluminum and Alumina-Particle Reinforced Aluminum Composite, Corrosion, Vol. 53, No. 2, 1997, pp. 136-141. 

When a plastic material is subjected to an external force, a part of the work done is elastically stored and the rest is irreversibly (or viscously) dissipated hence a viscoelastic material exists. The relative magnitudes of such elastic and viscous responses depend, among other things, on how fast the body is being deformed. It can be seen via tensile stress-strain curves that the faster the material is deformed, the greater will be the stress developed since less of the work done can be dissipated in the shorter time. 

Better cross-linking with the latter also improves post Tg viscoelastic responses of the rubber vulcanizates. Similar effect has also been observed with polychloroprene as investigated by Sahoo and Bhowmick [41]. Figure 4.8 represents the comparative tensile stress-strain behavior of polychloroprene rubber (CR) vulcanizates, highlighting superiority of the nanosized ZnO over conventional rubber grade ZnO [41]. 

Fig. 2.10. Schematic of the stress-strain response of a cylindrical specimen under tensile loading. Elastic response is obtained only in the initial linear region of the loading curve.

Each type of propellant has specific mechanical characteristics, but the influence of test parameters (temperature, strain rate, and pressure) is the same for all propellants (11). Tensile tests are widely used to analyze propellant behavior as well as examine the manufacturing controls of the propellants. Because their behavior is not linear-elastic, it is necessary to define several parameters that allow a better representation of the experimental tensile curve. The stylistic experimental stress-strain response at a constant strain rate from a uniaxial tensile test is shown in Figure 7, where E is the elastic modulus (initial slope), Sr P is the tensile strength (used later for a failure criterion), and eXj> is the strain at tensile strength. 

Stress-strain Response. As shown In Table V, the Incorporation of the reactive diluent to a level of 25% resulted In a slight decrease In Young s modulus, an Increase In % elongation at break, and little or no effect on tensile strength. However, the plasticizing effect of the diluent becomes quite marked at a diluent concentration of 50%. At this concentration, the crambe... 

In a heterogeneous blend, the details of the morphology do not generally exert much influence on the stress-strain tensile response. Contrary to expectation that the continuous phase would have more influence, the stress-strain response of unfilled EPDM-BR blends was found to be unaffected by a change in the BR domains from continuous to disperse (Morrisey, 1971). 

The challenges inherent in the measurement of stress-strain response of thin film materials by means of direct tensile testing are commonly more than offset by the distinct advantage that properties characterizing deformation resistance of the material in the plastic range can be determined under isothermal conditions for a relatively simple state of stress on the specimen. However, these techniques are not readily amenable to modifications that can accommodate uniaxial compression, simple shear stress, equi-biaxial stress or states stress on the specimen. As a result, it is difficult to draw conclusions concerning the dependence of plastic response on stress path history. It is noted that results for some cyclic tension-compression experiments were reported by Hommel et al. (1999). 

Stress-Strain Behavior of Polypropylene Both tensile and compressive stress-strain response of polypropylene is shown in Fig. 3.9. Quite obviously, the behavior in tension and compression are quite different for stresses above about 2,000 psi. This indicates that care must be used in analysis where the behavior in tension and compression are assumed to be the same. (See Rybicky and Kanninen (1973) for an example of the difference on the analysis of a beam in 3-point bending.)... 

Typical examples of tensile (isochronous) linear and nonlinear stress-strain diagrams for elastic and viscoelastic materials are shown in Fig, 10.1. For elastic materials, the response is time independent, so there is a single curve for multiple times and the nonlinearity is apparent as a deviation of the stress-strain response from linear. For linear viscoelastic materials, the isochronous response is linear, but the effective modulus decreases with time so that the stress-strain curves at different times are separated from one another. When a viscoelastic material behaves nonlinearly, the isochronous stress-strain curves begin to deviate from linearity at a certain stress level. Fig. 10.2 shows creep compliance data for an epoxy adhesive as a function of stress level for various time intervals after initial loading. 

Other less well-known types of nonlinearities include interaction and intermode . In the former, stress-strain response for a fundamental load component (e.g. shear) in a multi-axial stress state is not equivalent to the stress-strain response in simple one component load test (e.g. simple shear). For example. Fig. 10.3 shows that the stress-strain curve under pure shear loading of a composite specimen varies considerably from the shear stress-strain curve obtained from an off-axis specimen. In this type of test, a unidirectional laminate is tested in uniaxial tension where the fiber axis runs 15° to the tensile loading axis. A 90° strain gage rosette is applied to the specimen oriented to the fiber direction and normal to the fiber direction and thus obtain the strain components in the fiber coordinate system. Using simple coordinate transformations, the shear response of the unidirectional composite can be found (Daniel, 1993, Hyer, 1998). At small strains in the linear range, the shear response from the two tests coincide. 

---