Fire Safety of Fiber-Reinforced Polymer Composite Structures in Marine Environments: Performance, Failure Mechanisms, and Protection Strategies

Fiber-reinforced polymer (FRP) composites, including carbon-, glass-, basalt-, and hybrid-fiber-reinforced polymers, are increasingly used in marine structures because of their high specific strength, low density, corrosion resistance, and design flexibility. When heated, however, polymer composites may soften, decompose, and ignite, causing delamination, loss of integrity, smoke and toxic-gas release, rapid temperature rise on the unexposed side, and degradation of post-fire mechanical performance. Marine service conditions, including moisture, salt spray, ultraviolet radiation, thermal cycling, and long-term aging, further complicate these responses. This narrative review synthesizes the published evidence on the combustion of FRP used in ships, its structural behavior during fires, its post-fire performance, environmental aging, and protective measures. The responses of carbon-fiber-reinforced polymer (CFRP), glass-fiber-reinforced polymer (GFRP), basalt-fiber-reinforced polymer (BFRP), hybrid laminates, and sandwich composites are examined in terms of reaction to fire, thermal insulation, structural integrity, and residual load-bearing capacity. The principal mechanisms include matrix pyrolysis, fiber–matrix debonding, delamination, char cracking, core degradation, and barrier detachment. Fire-retardant resins, phenolic systems, intumescent coatings, thermal-insulation layers, inorganic barriers, and hybrid structural designs are critically reviewed. Finally, research needs are identified in coupled aging-fire testing, structural-scale fire experiments, standardized assessment protocols, and performance-based fire design for marine FRP composite structures.