In an embodiment, a fuel cell includes: a flexible substrate including a first fuel-tolerant material; a fitting on the flexible substrate, the fitting including first openings extending through an outer portion of the fitting; a primer coating on the outer portion of the fitting, the primer coating including a second fuel-tolerant material; first yarns strung through the first openings of the fitting, the first yarns stitched into the flexible substrate; and an encapsulant encapsulating the first yarns, the primer coating, and the outer portion of the fitting, the encapsulant disposed on the flexible substrate, the encapsulant including a third fuel-tolerant material, the third fuel-tolerant material chemically bonded to the second fuel-tolerant material and the first fuel-tolerant material.