Tensile breaking stress

It has been calculated that the strength of a weak plane in the transverse (vertical) direction must be less than one-fifth of the tensile breaking stress in order to induce a crack to turn sideways [24]. Lake et al. [25] considered the energy release rate Gs available for further growth of a sideways crack that is already long, and concluded that Gs is a rather small fraction of the value Gp for forward growth ... 

Figure 8. (a) Tensile breaking stress (directly proportional to... 

Teflene, 302 Teflon, 25,258,438 Teflon-impregnated polyester, 346 temporary vena cava Alters, 530-1 schematic diagram, 531 tenadty, 28-9 tensile breaking stress, 240 tensile strength, 76 TephaFlex, 236,237,278,289-92 Terylene, 295... 

Figure 5 Effects of filler content on tensile break stress of BaS04 filled compounds.

Most solid surfaces are marred by small cracks, and it appears clear that it is often because of the presence of such surface imperfections that observed tensile strengths fall below the theoretical ones. For sodium chloride, the theoretical tensile strength is about 200 kg/mm [136], while that calculated from the work of cohesion would be 40 kg/mm [137], and actual breaking stresses are a hundreth or a thousandth of this, depending on the surface condition and crystal size. Coating the salt crystals with a saturated solution, causing surface deposition of small crystals to occur, resulted in a much lower tensile strength but not if the solution contained some urea. 

Bnich-kupfer, n. scrap copper, -last, /. breaking load, -metall, n. broken metal, scrap metal, -modul, m. modulus of rupture, -probe, /. breaking test, breakdown test, -punkt, m. breaking point, -riss, m. (Meial.) failure crack, -silber, n. broken silver, scrap silver, -spaonung,/. breaking stress tensile strength, -stein, m. quarry stone broken stone, -stelle,/. broken place, place of fracture. -strich, m. (Math.) fraction stroke (between numerator and denominator), -stiick, n. fragment shred, -stiicke, pi. debris scrap, -teil, m. fraction, -zahl, /. fractional number. 

Table 1 Typical physical and (room temperature) mechanical properties (melting point Tm, glass transition temperature Tg) Young s modulus E, Izod toughness, tensile yield stress av elongation at break b) and applications of commodity polyolefins...

The main experimental methodology used is to directly characterize the tensile properties of CNTs/polymer composites by conventional pull tests (e.g. with Instron tensile testers). Similarly, dynamic mechanical analysis (DMA) and thermal mechanical analysis (TMA) were also applied to investigate the tensile strength and tensile modulus. With these tensile tests, the ultimate tensile strength, tensile modulus and elongation to break of composites can be determined from the tensile strain-stress curve. 

Tensile Yield Stresses of Cast Films. At room temperature all of the BPFC-DMS polymers investigated (with one exception) reached their yield stresses before fracturing. BPF polycarbonate on the other hand is brittle, breaking at about 11,000 psi. Traces of residual chloroform make the homopolymer ductile however the yield stress decreased linearly with chloroform content. Extrapolation of these results to a dry polymer gives a yield stress of 14,000 psi. 

Breaking stress Applied stress Tensile stress... 

Product Tensile modulus Stress yield IS0527-1, -2 IS0527-1, -2 (MPa) (N/mm2) (MPa) (N/mm2) Nominal strain Strain yield break IS0527-1, -2 IS0527-1, (%) -2 (%) ... 

The maximum strain rate (e < Is1) for either extensional rheometer is often very slow compared with those of fabrication. Fortunately, time-temperature superposition approaches work well for SAN copolymers, and permit the elevation of the reduced strain rates kaj to those comparable to fabrication. Typical extensional rheology data for a SAN copolymer (h>an = 0.264, Mw = 7 kg/mol,Mw/Mn = 2.8) are illustrated in Figure 13.5 after time-temperature superposition to a reference temperature of 170°C [63]. The tensile stress growth coefficient rj (k, t) was measured at discrete times t during the startup of uniaxial extensional flow. Data points are marked with individual symbols (o) and terminate at the tensile break point at longest time t. Isothermal data points are connected by solid curves. Data were collected at selected k between 0.0167 and 0.0840 s-1 and at temperatures between 130 and 180 °C. Also illustrated in Figure 13.5 (dashed line) is a shear flow curve from a dynamic experiment displayed in a special format (3 versus or1) as suggested by Trouton [64]. The superposition of the low-strain rate data from two types (shear and extensional flow) of rheometers is an important validation of the reliability of both data sets. 

Wall thickness uniformity is often compromised when fabricating near the material break point. Thinner walls are expected in the most stretched regions, but only if the melt is not allowed to recoil after cessation of flow. Often fabrication conditions are selected to be well away from the break point to minimize these issues. Key break point metrics for the startup of data illustra-trated in Figure 13.5 are the time /b and tensile stress coefficient rj (e,ti,) at break. Both quantities may be multiplied by the strain rate e to estimate the Hencky break strain (sb = tb s) and the break stress (tTb = kr (s, t)). Similar metrics can be defined for other startup extensional flows. 

Tensile Properties. Stress-strain data for the M-E-23/25-48 series is shown in Figure 16. Elongations at break drop rapidly with lower DBTDL concentrations. Young s modulus was measured at about 42 MPa (6,000 psi). Similar results were obtained in samples of the M-B-40/15-49 series where Young s modulus in this case was ca. 60MPa (8,700 psi). 

Figure 8.5 compares tensile yield stress for PP with two fillers. In both cases, tensile yield stress decreases significantly as filler concentration increases. At higher concentrations of talc (values above 0.15 are not plotted on Figure 8.5), the composite breaks without yielding. The difference is explained by the crystallization behavior of polypropylene on the filler surface which changes the mechanical properties of composite. This shows that an additional parameter (the orientation of the polymer) may play a role in tensile yield stress behavior. 

In the case of metal adherends with their high strength, the adhesive layer is the weakest link in the strength chain under tensile stress in case (a). Stressed by force F, the adhesive layer in such a bonded joint will break. In case (b), under tensile shear stress, the adhesive layer can be expanded to a certain extent (see Section 10.2.2) by enlarging the overlap length lu, and a bigger force F can be transmitted. In general, bonded joints require sufficient adherend surfaces. 

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