Distribution optimization strategy inspired by natural structure considering the ignition modes of plant fiber reinforced composites in real fire scenarios

Considering the ignition modes of interior structural components made from plant fiber reinforced composites (PFRP) in real fire scenarios, flame-retardant composites with corresponding structure were developed, inspired by the sandwich structure of cell membranes and the gradient structure of spruce found in nature the structure of spruce and cell membranes in nature. This work successfully prepared composites with sandwich structure (S-PFRP) and gradient structure (G-PFRP), which reduced the amount of added flame retardant by 33.3 % and 50 %, respectively, compared to traditional methods of random distribution. The thermal stability of S-PFRP and G-PFRP was significantly enhanced, with residues increasing by 131 % and 90 % at 800 °C compared to pristine PFRP, indicating excellent high-temperature stability. Adding only 5.1 % (S-PFRP) and 3.8 % (G-PFRP) of flame retardant was sufficient to achieve self-extinguishing properties, with LOI increasing by 72.2 % and 34.6 % compared to PFRP, and peak heat release rate decreasing by 47.1 % and 60.8 %. Furthermore, thanks to the excellent adhesion properties and good interfacial interaction with the resin of the designed flame-retardant system, the flexural strength of S-PFRP and G-PFRP were increased by 10.3 % and 7.1 % compared to pristine PFRP. The storage modulus at 50 °C of S-PFRP and G-PFRP was enhanced by 40 % and 28 %, respectively. Additionally, the incorporation of conductive graphene nanosheets (GNS) provided the composites with electromagnetic shielding properties, with total shielding values (SE_T) increasing by 26.1 dB and 21.7 dB at 8.2 GHz, representing a 20-fold improvement over pristine PFRP (1.8 dB).