Interfacial Microstructures and Properties of Silicone Resin Composites by Chemically Grafting Different Functional Polyhedral Oligomeric Silsesquioxanes Onto Carbon Fibers

By designing interface microstructures and interactions, bulk properties of carbon fiber (CF) reinforced polymer composites have been improved obviously. Here, maleamic acid‐isobutyl polyhedral oligomeric silsesquioxanes (MAI‐POSS) and octamaleamic acid‐POSS (OMA‐POSS) were separately modified onto fiber surface by the chemical bonding for enhancing interfacial strength of methylphenylsilicone resin (MPSR) composites. The microstructures and properties between CF and matrix resin were investigated. Two different POSS cages distributed onto the fiber surface uniformly, and enhanced surface roughness greatly (91.3 and 92.8 nm). However, OMA‐POSS grafted CF (CF‐g‐OMAPOSS) showed higher polarity and surface free energy than those of MAI‐POSS grafted CF (CF‐g‐MAIPOSS) owing to the introduction of abundant carboxyl groups onto fiber surface by OMA‐POSS grafting. Interfacial strength of modified composites enhanced significantly, especially for CF‐g‐OMAPOSS composites, which revealed the increases of 16.62% in interlaminar shear strength (ILSS) and 25.47% in interfacial shear strength (IFSS) compared to those of MPSR composites reinforced with CF‐g‐OMAPOSS. Interfacial reinforcing mechanisms of composites have also been analyzed and compared. In addition, the introduced strong SiOSi bonds in fiber–matrix interface were the main contributor for the obvious enhancement of hydrothermal aging resistance. POLYM. COMPOS., 40:E714–E722, 2019. © 2018 Society of Plastics Engineers