Study On Creep Property Of Epoxy Package Structure Of Micro Fuel Cell And Its Effect On The Cell Performance

Micro direct methanol fuel cell (μDMFC) has broad application prospects because of its high efficiency and cleanness. A reliable package is essential to DMFC. AμDMFC with an entire epoxy resin package structure was designed and fabricated. For the reason that epoxy resin has creep behavior under thermal-mechanical load, this paper studied the change process of the working plane in membrane electrode assembly (MEA) with the creep behavior of epoxy resin package structure, in the method of mechanics experiments and numerical simulation.Firstly, a passiveμDMFC with an entire epoxy resin package structure was designed and fabricated. The fuel cell structure was divided into two parts:internal structure and package structure. The internal structure, which was composed of MEA and two current collectors, was clamped by epoxy resin package structure that was made by potting. The test system for DMFCs established by the research group was used to test the performance of theμDMFC, and experimental results showed that the passiveμDMFC with 4mol/L methanol had a maximum power density of 5.256mWcm-2 at room temperature, which indicated that epoxy resin was feasible forμDMFC packaging.Secondly, the paper introduced the creep of polymer. Some basic theories to solve creep problem and some primary factors influencing creep behavior were presented. The time hardening theory was selected to research the creep process of epoxy resin package structure. In addition, the elastic tensile tests and tensile creep tests for package epoxy resin were accomplished. Besides that, the test for determining the coefficient of thermal expansion was also conducted. The paper processed the experimental data and got the relevant parameters for the simulation based on time hardening theory.Thirdly, this paper built theμDMFC finite element model for analyzing creep behavior of package structure, and adopted ANSYS software to simulate the change process of the MEA contact condition under thermal-mechanical load. Simulation results showed that because of the effect of creep, the overall normal stresses of the working plane in MEA increased with the increase of thermal-mechanical load cycles. After the cell became stable, the average normal stresses increased by about 0.08Mpa. Finally, using orthogonal test, the paper analyzed the effects of structure parameters on the contact state of the working plane in MEA, which contained the hole diameter of the current collector, the outer diameter and the thickness of the epoxy package structure. By evaluating the mean change and the uniformity of the normal stresses of the working plane in MEA, the paper calculated the 25 sets of finite element models ofμDMFC packaged by epoxy. The results showed that the most important parameter was the hole diameter of the current collector, the second important parameter was the thickness of the epoxy package structure and the least important parameter was the outer diameter of the epoxy package structure. Through orthogonal test, the author gained the optimized parameters of cell structure.