Composite manhole covers are not made from a single material but are a general category encompassing various composite materials. Common types include:
- Resin composite manhole covers: Made using unsaturated polyester resin as the matrix, reinforced with glass fiber, and formed via high-temperature, high-pressure compression molding.
- Magnesite manhole covers: Made using modified magnesite cement as the binder and incorporating fillers, reinforced with glass fiber and bamboo reinforcement bars.
- FRP (Fiber-Reinforced Plastic) manhole covers: Made using glass fiber (and glass fiber products) as the reinforcement material and synthetic resin as the matrix; technically known as glass fiber-reinforced plastic.
- SMC/BMC manhole covers: Made using Sheet Molding Compound (SMC) or Bulk Molding Compound (BMC) and formed through a single-step, high-temperature, high-pressure compression molding process; characterized by a high degree of polymerization and high density.
