Low-velocity impact responses and failure mechanisms of CFRP after fire exposure

Damage to composite laminates in a fire will significantly affect their structural integrity and post-fire performance. Here, we investigate the low-velocity impact (LVI) responses and failure mechanisms of CFRP with normal and flame-retardant epoxy resin after exposure to fire. When exposed to fire, the cases with normal resin lose more mass than those with flame retardant. Especially at 600 °C and 800 °C, the mass loss increases sharply, resulting in the visibility of fibers on the surface. Then LVI tests are conducted to evaluate the effects of the post-fire on the impact resistance. According to the experimental results, the specimens with normal resin have better impact resistance. When burning on both types of specimens, a higher ultimate contact force is observed later in the force-time curves. As a result of fire, the stiffness of the laminates degraded, changing their energy absorption mechanism. Nevertheless, when the temperature reaches 800 °C, more interfacial delamination and a new shear failure mode are observed in both types of specimens. Besides, the specimens with flame-retardant epoxy resin show excellent performance on the LVI testing after flaming of 800 °C.