Development and Validation of a Uniaxial Nonlinear Viscoelastic Viscoplastic Stress Model for a Fuel Cell Membrane

2015 ◽  
Vol 12 (6) ◽  
Author(s):  
Jessica A. May ◽  
Michael W. Ellis ◽  
David A. Dillard ◽  
Scott W. Case ◽  
Robert B. Moore ◽  
...  
Keyword(s):  
Vinylidene Fluoride ◽  
Numerical Models ◽  
Proton Exchange ◽  
Mechanical Degradation ◽  
Stress Model ◽  
Creep Stress ◽  
Nonlinear Viscoelastic ◽  
Uniaxial Creep ◽  
Poly Vinylidene Fluoride ◽  
Development And Validation

Proton exchange membranes (PEMs) in operating fuel cells are subjected to varying thermal and hygral loads while under mechanical constraint imposed within the compressed stack. Swelling during hygrothermal cycles can result in residual in-plane tensile stresses in the membrane and lead to mechanical degradation or failure through thinning or pinhole development. Numerical models can predict the stresses resulting from applied loads based on material characteristics, thus aiding in the development of more durable membrane materials. In this work, a nonlinear viscoelastic stress model based on the Schapery constitutive formulation is used with a viscoplastic term to describe the response of a novel membrane material comprised of a blend of perfluorocyclobutane (PFCB) ionomer and poly(vinylidene fluoride) (PVDF). Uniaxial creep and recovery experiments characterize the time-dependent linear viscoelastic compliance and the fitting parameters for the nonlinear viscoelastic viscoplastic model. The stress model is implemented in a commercial finite element code, abaqus®, to predict the response of a membrane subjected to mechanical loads. The stress model is validated by comparing model predictions to the experimental responses of membranes subjected to multiple-step creep, stress relaxation, and force ramp loads in uniaxial tension.

Development and Validation of a Non-Linear Viscoelastic Viscoplastic Stress Model for a PFCB/PVDF Fuel Cell Membrane

2012 ◽  
Author(s):  
Jessica A. Wright ◽  
Michael W. Ellis ◽  
David A. Dillard ◽  
Scott W. Case ◽  
Robert B. Moore ◽  
...  
Keyword(s):  
Polyvinylidene Fluoride ◽  
Numerical Models ◽  
Proton Exchange ◽  
Mechanical Degradation ◽  
Stress Model ◽  
Uniaxial Creep ◽  
Non Linear ◽  
Viscoelastic Modulus ◽  
Linear Viscoelastic ◽  
Development And Validation

Proton exchange membranes (PEMs) in operating fuel cells are subjected to varying thermal and hygral loads while under mechanical constraint imposed within the compressed stack. Swelling during hygrothermal cycles can result in residual in-plane tensile stresses in the membrane and lead to mechanical degradation or failure through thinning or pinhole development. Numerical models can predict the stresses resulting from applied loads based on material characteristics, thus helping to guide the development of more durable membrane materials. In this work, a non-linear viscoelastic stress model based on the Schapery constitutive formulation is used with a Zapas-Crissman viscoplastic term to describe the response of a novel membrane material comprised of a blend of perfluorocyclobutane (PFCB) ionomer and polyvinylidene fluoride (PVDF). Uniaxial creep and recovery tests are used to establish the time dependent linear viscoelastic modulus as well as the fitting parameters for the non-linear viscoelastic viscoplastic model. The stress model is implemented in a commercial finite element code, Abaqus®, to predict the response of a membrane subjected to mechanical loads. The stress model is validated by comparing predicted and experimental responses for membranes subjected to stress relaxation and multiple step creep loads in uniaxial tension.

Preparation and Characterization of Modified PVDF-g-PSSA Membrane

2010 ◽  
Vol 152-153 ◽  
pp. 44-50 ◽  
Author(s):  
Gui Bao Guo ◽  
Er Ding Han ◽  
Sheng Li An
Keyword(s):  
Relative Humidity ◽  
Sodium Silicate ◽  
Room Temperature ◽  
Proton Exchange Membrane ◽  
Vinylidene Fluoride ◽  
Proton Exchange ◽  
Poly Vinylidene Fluoride ◽  
Relative Humidity Range ◽  
Exchange Membrane

A new method based on a solution graft technique was used to prepare poly (vinylidene fluoride) grafted polystyrene sulfonated acid (PVDF-g-PSSA) proton exchange membrane. Polystyrene is grafted into PVDF modified by plain sodium silicate (Na4SiO4). There is a linear relationship between the degree of grafting and the content of Na4SiO4. Fourier transform infrared spectroscopy is used to characterize changes of the membrane's microstructures after grafting and sulfonation. The morphology of the membrane's microstructures after grafting and sulfonation is studied by scanning electrolytic microscope (SEM). The effect of plain sodium silicate (Na4SiO4) concentration and relative humidity on the conductivity of the electrolyte was investigated by the impedance at room temperature. The results show that the styrene has been grafted into PVDF. The conductivity of PVDF-g-PSSA electrolyte doped 10% plain sodium silicate (Na4SiO4) is 0.016 S/cm at room temperature. The conductivity of the electrolyte changes slightly at a relative humidity range of 20%-70%. The weightlessness of PVDF-g-PSSA electrolyte heated to 40°C was less than 2%, which indicated that water capacity was good.

Structure and Morphology of PVDF-G-PAMPS Membrane

2011 ◽  
Vol 197-198 ◽  
pp. 1321-1324 ◽  
Author(s):  
Gui Bao Guo ◽  
Sheng Li An
Keyword(s):  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Sulfonic Acid ◽  
Proton Exchange Membrane ◽  
Vinylidene Fluoride ◽  
Proton Exchange ◽  
Pvdf Membrane ◽  
Structure And Morphology ◽  
Poly Vinylidene Fluoride ◽  
Exchange Membrane

A proton exchange membrane of blended poly (acrylamido-2- methylpropane sulfonic acid) (PAMPS) grafted onto modified poly (vinylidene fluoride) (PVDF) membrane (PVDF-g-PAMPS) was prepared. Fourier transform infrared spectroscopy is used to characterize changes of the membrane's microstructures after grafting. The morphology of the membrane's microstructures after grafting is studied by scanning electrolytic microscope.The results show that 2-acrylamido-2-methylpropane sulfonic acid is easily grafted into PVDF modified by Plain sodium silicate (Na4SiO4).

Influencing Factors of Modified PVDF Grafted onto a Blended PAMPS(PVDF-G-PAMPS) Membrane

2011 ◽  
Vol 197-198 ◽  
pp. 1267-1270
Author(s):  
Jia Xu ◽  
Gui Bao Guo ◽  
Sheng Li An
Keyword(s):  
Reaction Temperature ◽  
Proton Exchange Membrane ◽  
Vinylidene Fluoride ◽  
Ammonium Persulfate ◽  
Proton Exchange ◽  
Reaction Conditions ◽  
Membrane Conductivity ◽  
Poly Vinylidene Fluoride ◽  
Exchange Membrane ◽  
Optimal Reaction

A proton exchange membrane of blended poly (acrylamido-2- methylpropane sulfonic acid) grafted onto modified poly (vinylidene fluoride) membrane (PVDF-g-PAMPS) was prepared The influences of Na4SiO4 content, reaction temperature and time, content of ammonium persulfate and AMPS on PVDF-g-PAMPS membrane were discussed. The results show that the optimal reaction conditions are as follows: Na4SiO4 is 8%; ammonium persulfate is 0.016 mol / L; AMPS is 30 %; the reaction temperature is 80 °C and the reaction time is 1h. On the condition, PVDF-g-PAMPS membrane conductivity can reach to 1.27×10-2 S/cm.

Studies on Preparation and Methanol Permeability of PVDF-g-PAMPS Membrane

2011 ◽  
Vol 335-336 ◽  
pp. 157-160 ◽  
Author(s):  
Jia Xu ◽  
Gui Bao Guo
Keyword(s):  
Sodium Silicate ◽  
Sulfonic Acid ◽  
Proton Exchange Membrane ◽  
Vinylidene Fluoride ◽  
Ammonium Persulfate ◽  
Proton Exchange ◽  
Methanol Permeability ◽  
Poly Vinylidene Fluoride ◽  
Methyl Pyrrolidone ◽  
Exchange Membrane

A proton exchange membrane of poly (vinylidene fluoride) grafted onto poly (2-acrylamido-2-methylpropane sulfonic acid) (PVDF-g-PAMPS) was prepared as follows: acrylamido-2-methylpropane sulfonic acid (AMPS) was first added to a N-Methyl pyrrolidone (NMP) solution containing poly (vinylidene fluoride) (PVDF) that was modified with plain sodium silicate. Ammonium persulfate was then added as an evocating agent and PAMPS was directly grafted onto the PVDF that was modified with plain sodium silicate. The influences of AMPS contents on the proton conductivity and methanol permeability were studied. The results showed that AMPS is easily grafted into PVDF modified by Plain sodium silicate (Na4SiO4), with increasing of the content of 2-acrylamido-2-methylpropane sulfonic acid, the methanol permeability became large gradually of PVDF-g-PAMPS membranes was increased.

Sign in / Sign up

Export Citation Format

Share Document