Manufacturing of Self-healing Carbon-fiber/Thermoplastic-toughened Epoxy Prepreg

Abstract

A self-healing prepreg containing solvent-filled microcapsules was manufactured using a specially designed and built laboratory scale prepregger. Carbon-fiber tow was used as reinforcing fabric and a mixture of poly (bisphenol a-co-epichlorohydrin) (PBAE) thermoplastic, EPON 828 epoxy, and 4,4′-diaminodiphenyl sulfone (DDS) hardener was used as matrix resin. Polymeric microcapsules with a double shell wall of polyurethane / ureaformaldehyde (PU/UF) containing ethyl phenylacetate (EPA) solvent were coated with polydopamine (PDA) to increase their solvent and thermal resistance and incorporated into the prepreg to impart self-healing functionality. The laboratory scale prepregger facilitated the fabrication of self-healing prepreg by continuously processing fiber sizing, resin impregnation, and fiber winding. A sizing agent was prepared by mixing microcapsules with butanone (MEK) solvent, and it was applied to a tow through a self-inking sizing drum which was covered by a consistent amount of the sizing agent. The tow then passed through matrix resin dissolved in MEK solvent to aid in an impregnation at room temperature, and the solvent was removed afterwards from the completed prepreg. Processing parameters for the prepreg fabrication were analyzed. Survival of microcapsules was examined using thermogravimetric analysis (TGA) and confocal fluorescent microscopy. A selfhealing laminated composite was manufactured using the prepreg after hot-pressing its laminate at 180 °C. The co-continuous matrix structure of the composite was examined using a scanning electron microscope.