A system (10) may include a seal (12) including a seal body (18) having an exterior (26, 30) with a seal interface. Additionally, the system includes a core (20) disposed internally within and surrounded by the seal body. A gas permeability of the core may be less than a gas permeability of the seal body, a coefficient of thermal expansion of the core may be less than a coefficient of thermal expansion of the seal body, or a combination thereof.