Direct observation of nanoparticle migration in epoxy based fiber reinforced composites using fluorescence microscopy

Abstract

The preferential accumulation of nanoparticles at carbon fiber surfaces, induced by the addition of a thermoplastic “migrating agent” to an epoxy resin, was monitored via in situ fluorescence microscopy. (3-Glydidyloxypropyl)trimethoxysilane functionalized fluorescent silica nanoparticles (GFCSP) were synthesized by a modified Stöber method to track the spatiotemporal abundance of nanoparticles. Single carbon fibers were embedded in an uncured epoxy mixture consisting of tetraglycidyl-4,4-diaminodiphenylmethane and 4,4’-diamnodiphenyl sulfone, as well as thermoplastic migrating agent, poly(ether sulfone), and GFCSP. A heated microscope stage was used to monitor the fluorescence in the local vicinity of the fiber as the epoxy begins to cross-link and solidify upon heating. Our results show that the synthesized GFCSP accumulate at fiber surfaces only in the presence of poly(ether sulfone), as verified using scanning electron micrographs of Mode I fiber fracture surfaces.