Date: Friday, October 31, 2003
Time: 3:00 p.m.
Place: 110 Othmer Hall
Fracture of advanced fiber-reinforced composites is influenced greatly by the fiber-matrix interface. Control of interfacial failure mechanisms through proper interface design is needed to further improve composite performance. Interface roughness is desired to provide a more tortuous crack path, which can lead to crack deflection and an increase in fiber pull-out friction, resulting in improved fracture toughness. A novel method of improving and controlling interfaces in advanced composites by using nanoparticles is presented here. Nanoparticles are used to reinforce and toughen the interface between the fiber and matrix. The nanoparticles are attached to the fiber to create multiple obstacles for the interfacial crack propagation. The objective of this thesis was experimental proof-of-concept. This work covered nanomanufacturing aspects as well as microscopic testing of the fiber interface.
Nanoparticles produced in our laboratory as well as commercially available nanoparticles were used to modify the surfaces of several commercially available advanced reinforcing fibers. Various deposition techniques and several methods of attaching nanoparticles to the fiber surfaces were explored. Electron microscopy was used to characterize the nanomanufactured fiber surfaces and particle-fiber bonding. Interfacial shear failure of the nanomodified systems was studied using the microbond test. Single fiber composite specimens were manufactured and tested. Analysis showed improvement of the interfacial properties in several nanoparticle-modified systems. Electron micrographs of failed specimens were used to evaluate the nanomechanisms of improvement. The results presented here provide proof-of-concept for nanoparticle surface engineering of composite interfaces and can be used in the development of next generation supertough lightweight composites for high performance structural applications.
