Effects of Mold Deformation and Heat Transfer on the Consistency of Composite Bipolar Plates

ABSTRACT Bipolar plates are multifunctional components of proton exchange membrane fuel cells, responsible for electron transfer, gas distribution, water management, and structural support. Compression molding dominates the manufacture of composite bipolar plates. Mold pressure and temperature govern plate properties, dimensional accuracy, durability, and safety. This study combines Finite Element Method and experiments to account for simultaneous mold deformation and heat conduction and quantifies how mold thickness affects pressure and temperature fields. A thick mold plus preheat strategy is proposed. Increasing mold thickness improves molding quality, but thicker molds develop marked temperature gradients that create regional property variations. A mold with a thickness of 40 mm reduces pressure non‐uniformity by 21.5%, while experimental and predicted values deviate < 5%. However, this change introduces a 4°C–10°C temperature difference of the mold forming surface. Consequently, mold preheating is mandatory. Under the tested material system and processing window, the optimized process yields composite bipolar plates with 143 S cm −1 electrical conductivity, 4.3 mΩ cm 2 contact resistance at 2 MPa, 1.9 × 10 −7 cm 3 cm −2 s −1 helium permeability, and 80.06 MPa flexural strength. These measured properties meet the Department of Energy standards and fuel cell requirements.