Effect of molecular motions on time-dependent fracture

Sacher, E.

doi:10.1080/00222347808212251

Cited by 11 publications

(3 citation statements)

References 43 publications

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“…Therefore, the rate-determining step for a single chain involves the stress-induced thermally activated molecular motions occurring at temperatures below glass transition temperature, T g leading to the failure of that chain. 49 These concepts formed the basis of the kinetic theory of fracture 48 which relates the lifetime τ, the stress σ, and the absolute temperature T with the following equation,…”

Section: Network Modelmentioning

confidence: 99%

“…where τ 0 is the time corresponding, in order of magnitude, to the period of fluctuation in the atomic bonding, U 0 is the binding energy of the polymer, and k is the Boltzmann's constant. This equation has also been known in the literature by other names such as the equation for polymer life, 49 the durability equation, 50 and the Boltzmann-Arrhenius-Zhurkov (BAZ) model. 51 Using Equation 2, the rate of failure due to mechanical stresses in each fiber of the network model can be deduced by the inverse relation given by,…”

Section: Network Modelmentioning

confidence: 99%

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Estimating the Durability of Polymer Electrolyte Fuel Cell Membranes Using a Fracture Percolation Model

Khattra

Hannach

Wong

et al. 2019

J. Electrochem. Soc.

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During fuel cell operation, the polymer electrolyte membranes are subjected to chemical and mechanical degradation that have an adverse impact on the membrane lifetime and thus overall durability of the fuel cell. To understand the synergistic effect of these two fundamentally different modes of degradation, it is therefore essential to consider both these effects when modeling membrane failure. A kinetic approach using a fracture percolation model is presented in this work that takes into consideration the hazard rates of chemical and mechanical degradation of the membrane incorporated into a two-dimensional membrane lattice network. While the chemical hazard rate is based on the rate of mass loss occurring during fuel cell operation, the mechanical hazard rate is evaluated based on a stress-induced, thermally activated process. The model captures the characteristic mechanisms of failure under the action of these fundamentally different modes, and converts the hazard functions into realistic time scale. The individual effects of the two modes are then incorporated in the model to predict in agreement with measured data, the time to fracture initiation in the membrane for a given combination of chemical and mechanical load.

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Section: Network Modelmentioning

confidence: 99%

Section: Network Modelmentioning

confidence: 99%

Estimating the Durability of Polymer Electrolyte Fuel Cell Membranes Using a Fracture Percolation Model

Khattra

Hannach

Wong

et al. 2019

J. Electrochem. Soc.

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“…The temperature and/or strain rate dependence of yield stress has been ascribed to Eying's rate theoryg-12 and the molecular motion occurring momentarily at the yield point is dominated by the relevant p r o c e~s e s .~~-~~ In addition, rate theory has also been applied to the time dependent fracture of polymeric materials. 18 In the light of these findings, a change in the relaxation process is expected to result in a corresponding change in the yield stress or vice versa.…”

Section: Introductionmentioning

confidence: 99%

Correlation between the mechanical behavior and relaxation processes in the plastically deformed polycarbonate

Hong

Brittain

1981

J of Applied Polymer Sci

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SynopsisThe low-temperature /3 relaxation has been studied via thermally stimulated depolarization current (TSD) method for polycarbonate that had been cold-rolled and subsequently undergone the a' relaxation at 70°C as a function of time. It has been found that the intensity of the p process increased as the annealing at 70°C increased. The analysis of the activation energy spectrum associated with the /3 relaxation indicated that the enhancement in the /3 intensity was due to the liberation of local dipoles from their aligned orientation as a result of undergoing the a' relaxation process. Tensile flow curves have also been determined for the same set of specimens. Similar enhancement was also observed in the yield stress behavior. In view of the good correlation between the mechanical property and the structural change revealed by the relaxation study, it was concluded that the variation of the yield stress and the work-hardening in the rolled polymer was primarily associated with those parts of the chain that had been disoriented from their frozen-in conformations.

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Molecular Mobility and Transitions in Polymers

Zlatkevich

1987

Polymers Properties and Applications

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Effect of molecular motions on time-dependent fracture

Cited by 11 publications

References 43 publications

Estimating the Durability of Polymer Electrolyte Fuel Cell Membranes Using a Fracture Percolation Model

Estimating the Durability of Polymer Electrolyte Fuel Cell Membranes Using a Fracture Percolation Model

Correlation between the mechanical behavior and relaxation processes in the plastically deformed polycarbonate

Molecular Mobility and Transitions in Polymers

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