Analytical and Experimental Analysis of Bending PEMFC Laminate Composite End Plates

To fasten a fuel cell stack in a polymer electrolyte membrane fuel cell (PEMFC), two thick steel endplates have been used to maintain a proper contact pressure at the interfaces among gaskets, gas diffusion layer (GDL), membrane electrode assemblies (MEA), and bipolar plates. The proper contact pressure is required both to improve its energy efficiency by decreasing ohmic loss and to prevent leakage of fluid such as hydrogen, air, or coolant. Since the thick steel endplates are not only heavy, but also have high thermal conductivity and thermal inertia, which deteriorate the cold-start characteristics of fuel cell stack, a new development of the endplate with light weight and better thermal properties is necessary.In this work, to satisfy the two functional requirements, i.e., light weight and good cold-start characteristics, a sandwich construction composed of carbon fiber reinforced composite faces and a thermal insulation foam core was employed for the endplate. For the endplate design, the axiomatic design process and finite element analysis were used considering both structural and thermal characteristics of the endplate of a PEMFC.The components of a fuel cell stack such as membrane electrode assemblies, gas diffusion layer, and bipolar plates of a PEMFC as shown in Fig. ۱, should be held together with sufficient contact pressure to prevent the side leakage of reactants and to minimize the contact resistance between adjacent unit cells in the stack, which has been accomplished by employing two thick steel endplates to maintain proper pressure distribution through the cells. For this end, the endplate should have high flexural stiffness to resist the high clamping force applied to its sides by bands or bolts, which have been used to give a proper contact pressure distribution in the stack. The low flexural stiffness of endplate may yield a non-uniform pressure distribution in the fuel cell stack. However, the weight of endplate should be reduced as much as possible for the passenger car application to obtain high mileage to fuel rate, which is difficult to accomplish with conventional metallic structures. Ha Na Yu and teammates study about a new design of asymmetric composite sandwich endplates which are made of carbon fiber reinforced composite and glass fiber reinforced composite with a pre-curvature generated by the residual thermal deformation [۱]. Mostafa Habibnia and counterpart's study about honeycomb sandwich panel structure of PEM fuel cell end plate. Their results were evaluated in two cases: with foam and no foam. After analyzing the experimental results, it has been concluded that the honeycomb sandwich panel structure for end plates has many advantages that makes it a good alternative to the old endplate structure [۲].In this study, different percent of carbon fiber and clay nano particle with various reinforce angle of laminate composite plates were investigated. First a square plate with specific material and size (as End plates) simulates with Abaqus software to specified optimum reinforce angles as shown in Figure ۱ and Figure ۲. So, the recognized that when reinforce angle is [۴۵,۰,۹۰, -۴۵] minimum deflection accrued. To achieve the best percentage of carbon fiber and clay nano particle two numerical (Abaqus software as shown in Figure ۴) and theoretical methods (FSDT) were used by using three-point bending method as described in D۷۹۰ standard. First-Order Shear Deformation Plate Theory in three point bending condition formed as [۳]:(.....)By two mentioned method Elastic Bending Modulus was obtained(.....)As shown in Error! Reference source not found. with ۶۰ percent of carbon fiber, ۲ percent of clay nanoparticle and ۸ layers of composite best strength obtain with minimum weight.