EFFECT OF SIZING ON THE INTERFACIAL AND MECHANICAL PROPERTIES OF CARBON FIBER (CF) REINFORCED POLYAMIDE (PA6,6) COMPOSITES

摘要

The interfacial characteristics of the fiber-matrix interface significantly influence the interfacial and mechanical properties of fiber-reinforced polymer composites. The interfacial properties of the fiber-resin interface can be altered physically or chemically by fiber surface treatment and sizing chemistries. These techniques may help increase the surface area and/or increase the surface functional groups on fibers, thus providing a pathway to chemical bonding between the fibers and the matrix resin. Sizing may further enhance interfacial adhesion by the formation of fiber-matrix interphase in composites. The choice of sizing is considerably dependent upon the polymer resin matrix to ensure the inter-diffusion of sizing interphase with the resin during processing. Similarly, the thickness and content of sizing on fibers also influence the mechanical and interfacial properties of the resulting composite. Presented here are the effects of fiber surface-treatment and sizing on the interfacial and mechanical properties of carbon fiber/Nylon (PA6,6) composites. After sizing commercial grade unsized carbon fibers (CF) with nylon compatible and incompatible sizing, an investigation of the influence of sizing architecture, thickness, and content on CF in the resulting composites commenced. Extraction and thermogravimetric analysis (TGA) determined the % loading of the sizing onto the carbon fibers. Sized carbon fibers were chopped and compounded with neat PA6,6 resin to prepare injection molded test bars for the investigation of tensile and flexural properties. Interfacial shear strength (IFSS) of the CF/PA6,6 composites was determined using the single-fiber pull-out method. Composite failure modes, established by utilizing SEM fractography, compared results to carbon fibers sized with an incompatible sizing for PA6,6 resin as well as unsized CF as a control. The results indicate that the choice of proper sizing significantly enhances the interfacial and mechanical properties of the CF/PA6,6 composite samples.