Collaborative: Brittle Epoxies Rendered Ductile- Crazing in Thermosetting Epoxy Nanocomposites

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Crazing is the phenomenon by which cracks in polymers are bridged by highly aligned polymer fibers. The addition of functionalized carbon nanotubes is found to initiate crazing in thermosetting epoxies which are a class of polymers that do not exhibit crazing. The objective of this project is to understand the mechanism by which crazing is initiated in thermosetting epoxy polymers by the addition of functionalized carbon nanotubes. To this end, the effect of structural changes induced by these nanotubes on the cure chemistry of the epoxy will be studied. The relationship between these structural changes and the mechanism of crazing will be established. Furthermore, the effect of multiscale static and dynamic stress heterogeneities on the mechanical response of the material will be studied. An ability to control crazing in thermosetting epoxies could significantly enhance their toughness and ductility without reducing their mechanical strength. Given the widespread use of epoxies in structural applications this is expected to translate into significant practical applications. The results of this work will provide a fundamental understanding of the mechanisms by which functionalized carbon nanotube additives can initiate crazing in thermosetting epoxies. This can lead to the development of a new class of nanocomposite thermosetting polymers with significantly enhanced toughness, ductility and fatigue resistance, while at the same time enhancing the strength and stiffness of the polymer. A variety of applications involving thermosetting epoxies such as paints, coatings, adhesives, industrial tooling, composites as well as the semi-conductor and electronics packaging industries will benefit from this research. In order to integrate research and teaching, specially designed interactive modules will be introduced into the curriculum as well as in the science courses taught at a science museum. The outreach activities will also include experimental demonstrations and presentations to high school students and teachers.