Fiber-reinforced polymer (FRP) composites are widely used in marine engineering fields, such as coastal construction, offshore bridges, submarines, and warships, owing to their light weight, high strength, and corrosion resistance. However, owing to the harsh marine environment, FRP composites used in the ocean are inevitably affected by seawater aging. Therefore, it is necessary to investigate the seawater aging properties of FRP composites. In this study, the seawater aging mechanism of FRP composites is summarized, and the influence factors (matrix type, fiber type, immersion temperature, loading mode, and aging method) of seawater aging on the mechanical properties of FRP composites are further reviewed in detail. Based on this, the method for improving the seawater resistance of FRP composites is summarized. In addition, the research schemes of accelerated aging of FRP composites and commonly used life prediction models are summarized, and the methods and suggestions for improving the accuracy of life prediction are further discussed.

To effectively overcome the shortcomings of common polyurethane (PU) insulation materials in terms of flame retardancy, mechanical properties, and sound absorption, a new multi-functional insulation material needs to be developed. Here, simple materials such as PU and silica aerogel (SA) combined with a special three-dimensional spacer fabric were used to design an innovative SA/PU/spacer fabric (SPS) ternary composite. It integrates a “hierarchically porous” and “filled-microperforated plate” structure. The superior structure design endows the new type of composite with a remarkable performance while maintaining low density (0.198 g/cm3). Specifically, the SPS composite was difficult to ignite by alcohol lamps compared with PU and SA/PU, and its thermal conductivity and compression modulus can reach 0.0392 W/(m·k) and 1.5 MPa, respectively. Moreover, the average absorption coefficient of the SPS composite (7.5 mm thickness) is 0.62, and its noise reduction coefficient per unit thickness (0.37) exceeds most reported sound absorption materials. From these results, the SPS composite provides a convenient and low-cost method to improve the overall performance of traditional thermal insulation material, which is of great significance in the fields of construction and transportation.