POSS-Based Fiber Carbon-Fiber Surface Treatment for Enhanced Durability of Composites

In the proposed study, we synthesize a clickable polyhedral oligomeric silsesquioxane (POSS) carbon fiber coating to enhance the fiber-matrix interfacial properties using the highly selective "thiol-ene click" chemistry. The unique hybrid structure of POSS molecules creates a spring-like effect when strongly bound to a surface, resulting in a smooth load transfer across the interphase region, making it uniquely suited for use as a fiber surface treatment to develop damage-tolerant composite laminates. This is the first study to date that reports on the use of "thiol-ene click" chemistry to create a controlled POSS coating to enhance the interfacial properties between the fiber and matrix. Thiol-ene chemistry is the reaction between a thiol (-SH) group and alkene group, creating a bond between the two materials. PAN-based carbon fibers undergo a series of chemical modification resulting in thiolated-carbon fibers. Octavinyl-POSS is selectively "clicked" to the carbon fiber surface, creating a strongly bound uniform POSS coating. These POSS-coated carbon fibers can now be used as a prepreg for the manufacturing of composites for aerospace applications requiring enhanced composite strength and durability. The fiber-matrix adhesion is characterized using fragmentation tests to determine the interfacial shear strength. Meanwhile, the surface treatment chemistry is characterized using FTIR and XPS techniques.