Effects of Frame Materials and Structures on Stress Concentration of Membrane Electrode Assembly of PEMFCs

Abstract

A membrane electrode assembly (MEA) is one of the core components of proton exchange membrane fuel cells (PEMFCs) comprising a catalyst coated membrane, gas diffusion electrodes, frames, and seals. By employing a 2D finite element model the mechanical stresses in membrane caused during the cell assembly procedure are analyzed for different MEA frame materials, frame structures and contact behaviors. The stress distributions in the membrane are presented and quantified. A zone with strong nonuniform stresses in the membrane under the end edge of frame/membrane is observed. The stepped frames assembly (SFA) and the bonded contact behaviors have more uniform stress distributions than the aligned frames assembly (AFA) does. The frame materials are not the main factors affecting the stress concentration in membrane for the SFA, while for the AFA the mechanical properties of frame materials should be close to those of the membrane. The results are expected to be helpful for people to select the frame materials and to design frame structures, and can be applied to guide the assembly of PEMFCs.

Review of Advanced Materials for Proton Exchange Membrane Fuel Cells

“…(d) Nafion has poor mechanical and chemical stabilities at elevated temperatures. − Being a part of an assembled MEA, the membrane suffers from severe degradation in the course of multiple thermal and hydration/dehydration cycles. − Because membrane mechanical degradation is typically the limiting parameter in determining FC lifetimes, substantial efforts were made to avoid or at least minimize this type of degradation. The membrane operational life also largely depends upon the MEA design and MEA assembly process. − The appropriate routes for improving the mechanical stability of a Nafion membrane are through the precise controls of membrane swelling, temperature, and temperature gradient ,− and the reinforcement of the membranes with an inert matrix, − which may be composed of a polymer structure ,,− or an inorganic matrix. Composite membranes comprising Nafion and inorganic fillers have been used.…”

Research Progress of Proton Exchange Membrane Failure and Mitigation Strategies

“…They disassembled the failed MEA and observed significant cracks at the junction area of the PEM and the frame near the hydrogen inlet. Ye and Kang et al simulated the stress distribution in the PEM and quantified the stress in the membrane [ 10 , 11 ]. Ye et al found that there is a serious non-uniform stress area in the junction area between the PEM and the frame.…”

“…Ye et al found that there is a serious non-uniform stress area in the junction area between the PEM and the frame. When the upper and lower frames are aligned, large deformation will occur in the boundary area between the PEM and the frame, resulting in the increase of shear stress [ 11 ]. Qiu et al presented a simulation and found that the stress-strain concentration in the junction region increased with the increase of temperature and water content, and plastic deformation even occurred in the PEM near the edge region [ 12 ].…”

“…The structure design of MEA plays an important role in improving the mechanical durability of membrane. Ye et al [ 11 ] observed a zone with strong nonuniform stresses in the membrane under the end edge of frame/membrane by simulation of different MEA frame materials, structures and contact behaviors. They found that the stepped frames assembly and the bonded contact behaviors have more uniform stress distributions as compared with the aligned frames assembly.…”

A Constitutive Model For Predicting The Time And Temperature-Moisture-Dependent Behavior Of Nafion Polymers

“…Ren found large in-plane compressive stresses caused by hydration swelling of the constrained membrane in the fuel cell [3]. Expansion and swelling caused by the cyclic hydrothermal conditions are also vital factors influencing the mechanical degradation [4,5]. Both Li et al [6] and Wu et al [7] performed accelerated stress tests on membranes by applying temperature and tensile cycles and found a rapid gas crossover rise and a quick performance reduction of fuel cells.…”