Elongation at failure

Mechanical properties, such as elastic modulus and yield point, that depend on crystallinity per se are not seriously affected by low to moderate doses of ionizing radiation. On the other hand, those mechanical properties that are sensitive to interlamellar activity are most dramatically affected by the low to moderate radiation doses. This is seen in the ultimate tensile strength and elongation at failure of the polyolefins. It is also reflected in the large change in melt index between 0 and 18 Mrad, which indicates formation of cross-links that increase with increasing... 

ZnO nanoparticles possess greater surface/volume ratio. When used in carboxylated nitrile rubber as curative, ZnO nanoparticles show excellent mechanical and dynamic mechanical properties [41]. The ultimate tensile strength increases from 6.8 MPa in ordinary rabber grade ZnO-carboxylated nitrile rubber system to 14.9 MPa in nanosized ZnO-carboxylated nitrile mbber without sacrificing the elongation at failure values. Table 4.1 compares these mechanical properties of ordinary and nano-ZnO-carboxylated nitrile rubbers, where the latter system is superior due to more rubber-ZnO interaction at the nanolevel. 

For Hq/Bp(50) PSF, the decrease in the elongation at failure with irradiation dose is significantly less than for Bis-A PSF. 

The increase in the modulus for Bis A PSF and Hq/Bp PSF with irradiation indicated that crosslinking predominated for both polymers and that the crosslink structures were probably basically similar. Hq/Bp(50) PSF was considerably more radiation resistant than Bis-A PSF, as shown by the rate of decrease in the elongation at failure. For both polymers, there was an initial rapid decrease in the elongation at failure followed by a slower decrease. This effect was also demonstrated by the variation in the fracture toughness (KI(.) with irradiation for Bis-A PSF. This work with cobalt-60 gamma radiation complements earlier studies of these materials using high dose rate electron beam irradiation (6). 

A strength increase is also produced at ultimate strength (F ) for steels however, the ratio f dynamic to static strength is less than at yield. A typical stress-strain curve describing dynamic and static response of steel is shown in Figure 5.5. Elongation at failure is relatively unaffected by the dynamic response of the material. 

Both siloxane-polyimide copolymers and BPADA-derived copolymers exhibited excellent solubility in a variety of dipolar aprotic solvents, including tetrahydrofuran, n-methylpyrrolidone, and dimethyl sulfoxide, as well as chlorinated hydrocarbons such as o-dichlorobenzene and methylene chloride. The polymers and copolymers were typical thermoplastics exhibiting little elongation at failure. The tensile properties are summarized in Table II. 

From Fig. 2a it is evident that as the test temperature raises from 0 up to 70 °C the resulting load-displacement curves display a decrease of the maximum load and an increase of the elongation at failure. On the other hand, as reported in Fig. 2b, when the displacement rate increases the load-displacement curves evidence an increase of the maximum load and, quite surprisingly, also the elongation at break increases. It is worth noting, that this rather unexpected rate effect on the load-displacement curves of notched samples has been already reported by Karger-Kocsis and co-workers for both biaxially oriented filled PET [7] and amorphous copolyester [9], and by Plummer et al. for polyoxymethylene tested at high temperature [14]. 

Mechanical Tensile Properties, measured according to ASTM D638 on 3-mil thick cured films of the conformal coating, are modulus of 1750 psi, tensile of 2000 psi, and elongation-at-failure of 285%. 

Polymer Density (p) (kgrn- ) Tensile strength cr (MPa) Elongation at failure (%) Cost ( /kg) (T lp... 

Small impregnated NbTi Cu Large NbTi Cu Filled epoxy Elongation at failure 0.4%... 

As expected, these adhesive layers showed the desired, very high elongation at failure. The specifications with regard to the slope of the force-deformation curve according to the elastic model could be readily met. However, the requirements for the ductile model could not be quite met because the initial stiff slope required by this model could not be attained. 

For concentrations above 30% of high isocyanate prepolymers, the resulting properties are not much different from the formulations with purely high isocyanate content. Below this concentration, the properties of the low isocyanate types were determined. A combination of effects (high elongation at failure, high slope of force-deformation curve) could not be observed. 

Fonnulation number Chemical basis of the prepolymer Main formulation components Best adhesive layer thickness (mm) Elongation at failure (mm) Tensile shear strength (MPa) Slope of force-deformation curve (N/mm)... 

For the measurement of tensile properties, dumb-bell specimens of the form shown in Fig. 2.13 are suggested. Tensile modulus. Poisson s ratio and elongation at failure may be measured with appropriate strain monitoring equipment and a set of stress/strain curves for a typical range of epoxies is given in Fig. 2.14. Similar... 

The most relevant mechanical properties of FRP for structural applications are the tensile strength, modulus of elasticity and the ultimate elongation at failure. Some representative values compiled from the literature are given in Table 5.2 for high performance long fibres suitable for structural applications. 

TABLE 2.27 Total Elongation at Failure of Selected Polymers... 

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