In the process of the coordinated development of polymer material and composite material technologies, polyurethane foam has become a key material in many fields due to its unique preparation process and adjustable performance advantages. As a polymer formed by mixing, reacting, and foaming two-component liquids (polyol and isocyanate) under the action of catalysts, foaming agents, etc., through high-pressure foaming equipment, polyurethane foam has derived three major categories—flexible foam, rigid foam, and semi-rigid foam—by virtue of differentiated structural design, accurately adapting to the functional needs of different scenarios. Among them, in the field of FRP composite materials, rigid polyurethane foam has become the core choice for sandwich structures due to its excellent mechanical properties and molding characteristics. Its innovative one-time composite molding process—PU raw materials are directly foamed and bonded between two FRP panels—can form a solid integral structure without bonding seams, which not only greatly improves the overall strength of the composite panel but also simplifies the production process, laying a solid foundation for the efficient application of FRP composite materials in the high-end manufacturing field.