The effect of nanoparticle inclusion on the tensile and mode I fracture properties of polyimides

Polyimide nanocomposites were fabricated using a combination of rotation/revolution mixing, layer-by-layer deposition and autoclave curing techniques. Seven different types of nanoparticles (25nm C, 20-30nm β-SiC, 130nm β-SiC, 10nm SiO_x (x=1.2-1.6), 80nm SiO₂, 11nm γ-Al₂O₃ and 40-80nm γ-Al₂O₃) and four different particle volume fractions (0.5, 1, 5 and 10vol%) were used for the inclusion. The effect of nanoparticle inclusion on the tensile properties and mode I fracture toughness was also investigated. The tensile modulus of the nanoparticle-filled polyimides was improved by the nanoparticle inclusion and increased with increasing volume fraction of the nanoparticles. No large differences in the tensile strength were observed for the nanoparticle-filled and unfilled polyimides. The mode I fracture toughness of the nanoparticle-filled polyimides was improved by C, β-SiC, SiO_x (x=1.2-1.6), SiO₂ and γ-Al₂O₃ nanoparticle inclusion and the maximum mode I fracture toughness, indicated by the critical stress intensity factor, was observed at approximately 5vol% nanoparticle content for each type of nanoparticle-filled polyimide.