Effect of boron carbide nanoparticles on the fire reaction and fire resistance of carbon fiber/epoxy composites

In this work the thermal behavior of a carbon-fiber composite impregnated with nano sized boron carbide based nanocomposites was investigated. First of all, the good dispersion and distribution of the particles in the matrix confirmed the effectiveness of the mechanical mixing. The presence of the ceramic filler did not affect the viscosity and the workability of the blends or the mechanical properties of the composites. The thermal stability of the fiber-reinforced materials was investigated by thermo-gravimetrical analysis in air and nitrogen. Their fire reaction was studied at different heat fluxes (35 and 50 kW/m2) by cone calorimeter while the flame resistance was evaluated trough residual mechanical properties after the exposition of the specimens to a direct flame of a torch (heat flux of 500 kW/m2). The experimental data suggested that boron carbide allows maintaining a residual structural integrity of the material after burning because of the chemical reactions that occur in the filler at high temperatures; the presence of boron carbide reduces the peak of heat release rate especially at higher heat-fluxes and improves the thermal stability of the composite hindering and retarding the thermal oxidation of the carbon fibers.