Compression stress-strain curves

Fig. 25.9. The compressive stress-strain curve for a polymeric foam. Very large compressive strains ore possible, so the foam absorbs a lot of energy when it is crushed.

Mills and Gilchrist (270) analysed the heat transfer that occurs when closed cell foams are subjected to impact, to predict the effect on the uniaxial compression stress-strain curve. Transient heat conduction from the hot compressed gas to the cell walls occurs on the 10 ms... 

The effect of gas compression on the uniaxial compression stress-strain curve of closed-cell polymer foams was analysed. The elastic contribution of cell faces to the compressive stress-strain curve is predicted quantitatively, and the effect on the initial Young s modulus is said to be large. The polymer contribution was analysed using a tetrakaidecahedral cell model. It is demonstrated that the cell faces contribute linearly to the Young s modulus, but compressive yielding involves non-linear viscoelastic deformation. 3 refs. 

Gas compression in closed-cell polymer foams was analysed, and the effect on the uniaxial compression stress-strain curve predicted. Results were compared with experimental data for a foams with a range of cell sizes, and the heat transfer conditions inferred from the best fit with the simulations. The lateral expansion of the foam must be considered in the simulation, so in subsidiary experiments Poisson s ratio was measured at high compressive strains. 13 refs. 

The fundamental shear and Young s moduli are the slopes of the shear and tension/compression stress/strain curves at the origin. The relationships given above are an attempt, with theoretical justification, to describe the shapes of the stress/strain curves at higher strains. Appreciation of this may avoid confusion between the absence of a single modulus figure for rubber whilst such values are quoted. 

The compression stress-strain curves obtained over quite a broad temperature range are shown in Fig. 15 [33]. It appears that the strain softening, weak and slightly temperature-dependent in the temperature range from 40 to 100 °C, increases when lower temperatures are considered. 

Fig. 16 Effect of strain rate on uni-axial compression stress-strain curves of PMMA a at - 50 °C and b at 50 °C (From [33])...

Fig. 68 Compression stress-strain curves for BPA-PC at various temperatures at a strain rate of 2 x 10-3 s 1 (From [53])...

Fig. 5.17 Unconfined compression stress-strain curves and experimentally measured temperature increase ATa as a function of strain for PS (Dow 685), LDPE (Dow 640), and PP (LG H670). The initial test specimen was at 26°C and the crosshead speed of the compressing har with the load cell was 25.4 mm/min. The specimen dimensions were 101 mm diameter and 71 mm height. [Reprinted by permission from M. H. Kim, Ph.D Thesis, Department of Chemical Engineering, Stevens Institute of Technology, Hoboken, NJ (1999).]...

Fig. 28. Dependence of the compressive stress-strain curves on strain rate of silica filled epoxy [46]...

Figure 4.24 Tensile and compressive stress-strain curves of PBZO fibers under different conditions as spun, as coagulated, and heat-treated (Martin and Thomas, 1989 Kumai 1990a). Note the very low strength in compression.

Figure 14.2 Compressive stress-strain curve to very high stress level.

Figure 3.24 Compressive stress-strain curves for natural rubber vulcanizate showing the effect of shape factor S. (From Ref. 24.)...

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. 

Figure 4.30P 1 shows the compressive stress-strain curves for latex-modified mortars. Generally, the maximum compressive strain at failure increases with rising polymer-cement ratio, even though there is no pronounced change in the modulus of elasticity in compression. The maximum compressive strain at a polymer-cement ratio of 20% increases to 2 to 3 times that of unmodified mortar. 

Figure 4.30 Compressive stress-strain curves for latex-modified mortars.

Figure 4.24 Compressive stress-strain curve for PU foam of density 31 kgm, compressed in-plane —, and through thickness —, compared with the Kelvin foam prediction for compression along [III] direction —...

Figure 7.17 Examples of tensile and compression stress-strain curves for reinforced plastics...

Unconfined compression Triaxial compression Stress-strain curve Undrained shear strength (CJ Young s modulus (E)... 

Fig. 8.1 Compression stress-strain curves of annealed and quenched PS at T = 296 K and at an extensional strain rate of e = 10 s , with a number of stress removals showing Bauschinger reverse strains (from Hasan and Boyce (1993) courtesy of Elsevier).

The calculated compressive stress-strain curves for the annealed and quenched structures are shown in Fig. 8.14, together with the experimental stress strain curves of Hasan and Boyce (1993). In the model curves only plastic strains were considered. This results in a shift between the experimental and modeling curves. This shift can be rationalized by noting that at the peak flow stress at yield, at which fully developed plastic behavior sets in, the pre-yield plastic strain is roughly equal to the elastic strain at the peak stress. Thus, while the lower strain axis gives only plastic strains, the total strain of the experimental curves that include the... 

For a second comparison we chose the strain-hardening behavior of nearly glassy PET between 298 K and the glass-transition temperature of 346 K, which was studied by Zaroulis and Boyce (1997) in compression flow. Figure 8.18 shows the compression stress-strain curves of PET at a strain rate of 10 s at seven temperatures between 298 and 349 K, slightly above Tg. The DSC experiments showed that as-received material contained nearly a 9% crystalline fraction. It also needs to be noted that PET undergoes considerable strain-induced... 

Fig. 8.18 Compression stress-strain curves of nearly glassy PET (crystalline content 9%) for seven temperatures reaching Tg, showing strong yield phenomena and strain-softening effects that decrease with increasing temperature, having a relatively temperature-independent entropic strain-hardening contribution (from Zaroulis and Boyce (1997) courtesy of Elsevier).

Typical compressive stress-strain curves of surfactant-containing hydrophobically modified hydrogels are shown in Fig. 15a, where results obtained from 15 separate HM PDMA hydrogel samples at a state of preparation are presented. The... 

Figure 11.11. Compressive stress-strain curves for concrete impregnated with poly(methyl methacrylate). Polymer loading MMAl > MMA2 > MM A3. Specimen L25 is a latex-modified concrete. (Dahl-Jorgensen and Chen, 1973.)...

Figure 11.12. Compressive stress-strain curves for concrete impregnated with various combinations of methyl methacrylate (MMA), n-butyl acrylate (BA), and a crosslinking agent, trimethylolpropane trimethacrylate (TMPTMA). Specimen BI, 90 MMA/10 TMPTMA ...

Figure 11.13. Polymer-impregnated concrete compressive stress-strain curves as a function of polymer composition (hydraulic tester) KSI = psi X 10". MMA and BA refer to methyl methacrylate and n-butyl acrylate, respectively. (Manson et al, 1973.)...

The model of Hess and Barrett was qualitative a few years later Frank and Stroh [135] proposed a more quantitative model in which they considered the energetics of the process that is the starting point for the microscale model (as discussed in the next section) that is currently used to qualitatively and quantitatively explain the typical response of the MAX phases to cyclic compressive and tensile stresses at room temperature (Figure 7.12). In Figure 7.12a are plotted typical cyclic compressive stress-strain curves for Ti3SiC2 with two different grain sizes. Also... 

Fig. 1.7 Compressive stress-strain curves [23]. With kind permission of Elsevier...

The unconfined compressive strength used in the above equation is 3,872 126 MPa, as seen in Fig. 1.46. A discussion about the effects of temperature and strain rates on the compression stress-strain curves is found in later sections dealing with ductile ceramics and the infiuence of impact on the strength properties of ceramics. 

The arrows in the curves indicate the locations where the tests were interrupted. In curves when no arrows are shown, the specimen has failed at the end of the curve. Deviation from linearity may be seen even at 1400 °C, but at this temperature and at 1500 °C, only slight plastic deformation was observed, in spite of the high compressive stress over 1000 MPa. At the same stress, a compressive strain of 7 % was obtained at 1600 °C. Yet, a compressive strain of about 11 % was achieved at 1700 °C at a lower compressive stress. Figures 2.6 and 2.7 illustrate compressive stress-strain curves at various strain rates at 1600 and 1700 °C. 

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