Title page for ETD etd-04222009-192729


Type of Document Master's Thesis
Author Grohs, Jacob R
URN etd-04222009-192729
Title Analysis and Modeling of the Mechanical Durability of Proton Exchange Membranes Using Pressure-Loaded Blister Tests
Degree Master of Science
Department Engineering Science and Mechanics
Advisory Committee
Advisor Name Title
Case, Scott W. Committee Chair
Dillard, David A. Committee Member
Ellis, Michael W. Committee Member
Keywords
  • lifetime prediction model
  • finite element analysis
  • digital image correlation
  • pressure-loaded blister test
  • proton exchange membrane
Date of Defense 2009-04-10
Availability restricted
Abstract
Environmental fluctuations in operating fuel cells impose significant biaxial stresses in the constrained proton exchange membranes (PEM). The PEM’s ability to withstand cyclic environment-induced stresses plays an important role in membrane integrity and consequently, fuel cell durability. In this thesis, pressure loaded blister tests are used to study the mechanical durability of Gore-Select® series 57 over a range of times, temperatures, and loading histories. Ramped pressure tests are used with a linear viscoelastic analog to Hencky’s classical solution for a pressurized circular membrane to estimate biaxial burst strength values. Biaxial strength master curves are constructed using traditional time-temperature superposition principle techniques and the associated temperature shift factors show good agreement when compared with shifts obtained from other modes of testing on the material. Investigating a more rigorous blister stress analysis becomes nontrivial due to the substantial deflections and thinning of the membrane. To further improve the analysis, the digital image correlation (DIC) technique is used to measure full-field displacements under ramped and constant pressure loading. The measured displacements are then used to validate the constitutive model and methods of the finite element analysis (FEA). With confidence in the FEA, stress histories of constant pressure tests are used to develop linear damage accumulation and residual strength based lifetime prediction models. Robust models, validated by successfully predicting fatigue failures, suggest the ability to predict failures under any given stress history whether mechanically or environmentally induced - a critical step in the effort to predict fuel cell failures caused by membrane mechanical failure.
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