Evaluation of residual strains in epoxy with different nano/micro-fillers using embedded fiber Bragg grating sensor

The influence of SiO2 nanoparticles and rubber micro-fillers on the mechanical and thermal responses of an epoxy based composite is investigated using classical quantitative thermo-mechanical testing (tensile tests, DMTA, TMA), microstructural analysis (Micro-CT, TEM, SEM microscopy) as well as distributed optical sensing in order to determine different residual strain fields generated during processing. The results show that the tensile modulus of the compounds increases with the addition of SiO2 and decreases with the rubber content, following estimates of the Hashin–Shtrikman model. The coefficient of thermal expansion appears to be insensitive to the particles’ content in the temperature range investigated. The residual strains generated during processing are influenced by the rubber content that introduces a strong relief, with respect to the one generated by the neat resin, whereas the silica content tends to increase their level.