ISSN:
0449-2978
Keywords:
Physics
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
The strength and extensibility of an unfilled styrene-butadiene rubber vulcanizate were determined in constrained biaxial tension (essentially pure shear) by stretching thinwalled cylindrical specimens in the axial direction with an Instron tester while gas pressure was admitted to maintain constant the outside diameter of a specimen. The rupture stress, λ1b, and the extension ratio, λ1b, in the axial direction and the rupture stress, σ2b, in the circumferential direction were determined at extension rates from 0.0031 to 3.1 min-1 and temperatures from 25 to 90°C. Rupture data in simple tension were also obtained by testing ring specimens under similar test conditions. The time-temperature shift factor, aT, obtained by superposing rupture data at different temperatures, gives a constant activation energy of 35 kcal. Doubly logarithmic plots were prepared showing the dependence of σ1b/λ1b, σ2b, and λ1b from the biaxial tensile tests and of σb/λb and λb from the simple tensile tests on the temperature-reduced extension rate, \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \lambda a_T $\end{document}. (The quantities σ1b/λ1b, σ2b, and σb/λb are rupture stresses based on the dimensions of undeformed specimens.) At equal values of \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \lambda a_T $\end{document}, the extension ratios λ1b and λb are sensibly identical. The ratios σ1b/σb and σ2b/σb, as well as λbσ2b/σb, were obtained from rupture data read from the composite curves at selected values of \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \lambda a_T $\end{document}. Also, similar ratios were derived from stress data at equal extensions in biaxial and simple tension for 1.25 ≤ λ ≤ 3.0, the range comparable to that in which rupture data were obtained. A consideration of the ratios given by both the rupture and the stress data shows that the von Mises failure criterion is not applicable, although the departure is small except at the larger values of λb.
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1969.160070407
