The unique wick effect and combustion behavior of flax fiber reinforced composites: Experiment and simulation

The mechanical properties of plant fiber reinforced composites present the characteristics of multi-scaled failure due to the presence of hierarchical microstructure, but there is no research concerning the effect of microstructure on the combustion characteristics. In this work, based on single variable principle, three specimens including neat epoxy (EP), carbon fiber reinforced composites (CFRP) and flax fiber reinforced composite (PFRP) were designed to systematically investigate the unique combustion characteristic and wick effect of PFRP via a series of methods. The results show that PFRP exhibits unique combustion characteristic where the heat release rate and smoke production rate show the characteristics of prolonged time span and multi-peaks. Additionally, PFRP expands in the thickness direction during the combustion and the char skeleton can be retained after the combustion. Besides, PFRP also exhibits different wick effect from CFRP where the linear burning rate and the temperature at same position of PFRP is slower and lower, meaning that the interfacial carbonation strategy for efficient flame retardance of traditional fiber reinforced composites is not the optimal solution for PFRP. And the unique wick effect is also verified via the finite element simulation method. The systematic study of PFRP combustion characteristics provides theoretical basis for designing targeted flame-retardant strategies to improve the fire resistance of PFRP.