Composites stress-strain properties

The table data show that the stress/strain properties of compositions are improved by additional dispersion (mixing). Ultrasonic analysis is sufficiently reliable and informative as a means of mixing quality assessment. The very small change of the characteristics for filled compositions (chalk + kaolin) can be due to the fact that these fillers are readily distributed in the matrix as they are. 

Figure 8. Comparison of the stress-strain properties of the press-quenched films of HBIB to those from the homopolymers HB and HI. Composition of each polymer is denoted by the butadiene content next to the graph.

The longitudinal stress-strain properties of all of the composites can be represented by the following empirical equations which have been found to represent the data satisfactorily ... 

Figure 17 illustrates the effect of orientation on the stress-strain properties of the rayon composite shown in Figures 10 and 11. The upper curve represents stress-strain behavior for stress applied parallel to the fiber orientation direction. In the lower curve the force is applied perpendicularly. Even a small degree of orientation has a large effect on the anisotropy of the composite. The differences in tensile strength, modulus and elongation at break in the two directions are considerable. 

The effect of temperature on the stress-strain properties of PMMA, its gradient polymers with various compositions, and an IPN are shown in Figures 7, 8, and 9. These experiments were performed at various strain rates at 60°C. Comparison with the 80°C data shows that the main effects of temperature are to increase the stress levels in the plateau regions at lower temperatures without significant differences in other aspects. 

In order to evaluate the commercial importance of bis(8-oxyquino-late)zinc(II) stabilization of PFAP, this stabilizer was evaluated in a standard PFAP O-ring formulation (Table III). Compound A should be considered as a control since no stabilizer was added. Compound B is identical in composition to A except that 3 wt % of stabilizer was added during the mixing of B on a rubber mill. Compound C was the same as A except the PFAP was treated with 3 wt % stabilizer in DMF (homogeneous) prior to mixing the compound. The stress-strain properties of cured specimens of B and C were essentially identical but appear to be of a lower cross-link density than A. 

HDPE/PP + two EPR s Tensile properties for different compositions Stress-strain curves, strength, modulus, yield stress, etc. D Orazio et al., 1983... 

Figure 4. Stress-strain properties of plasticized LP-32 polymer based compositions (see Table V for formulations)...

EFFECT OF ACRYLATE FUNCTIONALITY ON STRESS-STRAIN PROPERTIES Composition Functionality Mol Wt Wt/Double Tensile Modulus ElonRation... 

The measurement of extension (or other mode of deformation) is an essential part of several tests, notably tensile or compression stress, strain properties and also thermal expan.sion. The range of measurement and the precision required depends not only on the type of deformation but on the material—there is clearly a big difference between a fiber reinforced composite and a soft rubber. Needless to say. the precision and range mu.st be specified in the individual test method, and it is unlikely to be the same as that required for test piece dimensions. The method of measurement will also be to a considerable extent dependent on the test in question, and specific techniques may in some cases be given. Hence, the requirements for particular tests will be discussed in the relevant sections in later chapters. 

The first true mechanical study was made by Schadler et al. in 1998. They measured the stress-strain properties of a MWNT poxy composite during both tension and compression. In tension, the modulus increased from 3.1 GPa to 3.71 GPa on the addition of 5 -wt% nanotubes, a reinforcement of d I7d V( = 18 GPa. However, better results were seen in compression, with an increase in the modulus from 3.63 to 4.5 GPa, which corresponds to a reinforcement of 26 GPa. No significant increases in the strength of toughness were observed. The difference between tension and compression was explained by Raman studies which showed significantly better stress transfer to the nanotubes in compression than in tension. This can be explained by the fact that load transfer in compression can be thought of as a hydrostatic pressure effect, whereas load transfer in tension relies on the matrix-nanotube bond. However, it should be pointed out that later studies showed the reverse to be true, Le. load transfer in tension but none in eompression. In further contrast, work by Wood et al has shown that the mechanical response of SWNTs in tension and compression are identical. 

Fi) . 6. (a) The observed stress-strain curve of wet wool. The stress in the middle of the yield region is 0.33 GPa and the maximum extension is 50%. (b) Predicted stre.ss-strain curve, thick line marked with arrows, based on the composite analysis of Fig. 7. The independent stress-strain properties of the components arc shown as ot-c -eq-fJ for the microfibrils (IFs) and M for the matrix. 

Fig. 12. A model for the stress-strain properties of viseose rayon. Hearle (1967). (a-c) Composite models of crystalline C and disordered D matedal in (a) lamellar L, (b) miecllar M. and (c) fibrillar F forms.

Dynamic Mechanical Properties n (1) The stress-strain properties of a material when subjected to an applied sinusoidally varying stress or strain. For a perfectly elastic material the strain response is immediate and the stress and strain are in phase. For a viscous fluid, stress and strain are 90° out of phase. (2) The mechanical properties of composites as deformed under periodic forces such as dynamic modulus, loss modulus and mechanical damping or internal friction. (Sepe MP (1998) Dynamic mechanical analysis. Plastics Design Library, Norwich, New York)... 

Modified ETEE is less dense, tougher, and stiffer and exhibits a higher tensile strength and creep resistance than PTEE, PEA, or EEP resins. It is ductile, and displays in various compositions the characteristic of a nonlinear stress—strain relationship. Typical physical properties of Tef2el products are shown in Table 1 (24,25). Properties such as elongation and flex life depend on crystallinity, which is affected by the rate of crysta11i2ation values depend on fabrication conditions and melt cooling rates. 

The mechanical piopeities of stmctuial foams and thek variation with polymer composition and density has been reviewed (103). The variation of stmctural foam mechanical properties with density as a function of polymer properties is extracted from stress—strain curves and, owkig to possible anisotropy of the foam, must be considered apparent data. These relations can provide valuable guidance toward arriving at an optimum stmctural foam, however. 

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