Improvement of fracture toughness and thermo-mechanical properties of carbon fiber/epoxy composites using polyhedral oligomeric silsesquioxane

The influence of polyhedral oligomeric silsesquioxanes-polyvinylpyrrolidone on the interlaminar fracture toughness of carbon fiber-reinforced composites (CFRPs) is investigated in this study. Baseline composite material is fabricated using novolac epoxy-infused carbon fiber prepreg. Glycidyl isobutyl polyhedral oligomeric silsesquioxanes (GI) is introduced in the CFRP at loading of 1, 3, 5, and 10 wt.% with respect to polyvinylpyrrolidone used as a compatibilizer. Results of the double cantilever beam test indicate an increase of 70% in interlaminar fracture toughness for 5 wt.% GI-POSS loading compared to the baseline composite. Scanning electron microscopy shows polyhedral oligomeric silsesquioxanes enhanced the adhesion between fiber and the resin that leads to the fiber pull-out. Dynamic mechanical analysis result captures the reduction in the storage modulus with addition of polyvinylpyrrolidone due to the plasticization effect. Nonetheless, the introduction of polyhedral oligomeric silsesquioxanes increases the storage modulus for the GI/PVP composite. Additionally, an increase in the glass transition temperature with the reinforcement of polyhedral oligomeric silsesquioxanes is observed.