The tensile stress–strain behavior of Nafion 117 and sulfonated poly(arylene ether sulfone) copolymer (BPSH35) membranes were explored with respect to the effects of the strain rate, counterion type, molecular weight, and presence of inorganic fillers. The yielding properties of the two films were most affected by the change in the strain rate. The stress–strain curves of Nafion films in acid and salt forms exhibited larger deviations at strains above the yield strain. As the molecular weight of the BPSH35 samples increased, the elongation at break improved significantly. Enhanced mechanical properties were observed for the composite membrane of BPSH35 and zirconium phenylphosphonate (2% w/w) in comparison with its matrix BPSH35 film. The stress‐relaxation behavior of Nafion and BPSH35 membranes was measured at different strain levels and different strain rates. Master curves were constructed in terms of plots of the stress‐relaxation modulus and time on a double‐logarithm scale. A three‐dimensional bundle‐cluster model was proposed to interpret these observations, combining the concepts of elongated polymer aggregates, proton‐conduction channels, and states of water. The rationale focused on the polymer bundle rotation/interphase chain readjustment before yielding and polymer aggregate disentanglements and reorientation after yielding. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1453–1465, 2006

No abstract

A brief characterization of the mechanical behavior of Nafion ® 117 and BPSH-35 membranes took place through uniaxial loading, stress relaxation, and creep com pliance tests. Membranes were subjected to uniaxial loading at various strain rates to observe yield and fracture behavior. Stress relaxation tests measured relaxation response to strain rate and relaxation strain. Creep compliance tests led to the for mation of a creep master curve for the Nafion ® membrane. Tests showed that for Nafion ® , higher strain rates produced higher yield stresses and yield strains as well as faster initial relaxation. Strain rate had no effect on strain at fracture. Higher re laxation strains also led to faster initial stress relaxation in both Nafion ® and BPSH. BPSH results showed no yield trends in uniaxial loading, though they illustrated lower breaking strains with higher strain rates.

Just three weeks after fracturing a bone in his forearm, the Hokies' star tailback, Cedric Humes, was able to return to his starting role with the help of materials science.

In metal matrix composites, the spacing between discontinuous reinforcements can affect strengthening by interfering with the motion of dislocations through the metal. This project looks for similar phenomena in polymer matrix composites (PMCs), since the molecular activity of the polymer chains should be altered in the vicinity of the reinforcements. Awareness of such a trend can improve the understanding of PMC mechanics, which in turn can improve PMC characterization and selection techniques. This project sought a relationship between particle spacing and overall strengthening in a discontinuously-reinforced PMC test case composed of alumina particles in a polyphenylene sulfide matrix. Tensile tests were run on hot-pressed composite samples with varying reinforcement volume fraction and particle size. Data showed that composite strength increases as particle spacing increases, except at high volume fractions where this trend reverses. These results provide preliminary data but demonstrate a need for more in-depth investigation.