Carbon fiber reinforced composite materials are well known for their high strength and stiffness, low weight and for the ability to tailor the fiber layup to obtain design specific performance. In laminate form the materials are built up from layers of fibers oriented at different angles and infused with epoxy resin that holds the fiber and layers together. Under impact and other loads fractures between fibers or between the layers can be introduced. The resistance of the laminate to such damage is strongly dependent on the toughness of the resin. The strength that remains after damage is also dependent on the resin toughness.
We are working with Cytec Engineered Materials to explore mechanisms of toughening of the resin as used in composite materials. This work will be primarily experimental but will also include extensive research of the literature in this area to gain an understanding of the state of the art in composite toughening. Experiments to be performed will include the use of SEM and micro-CT imaging to visualize and quantify deformations during interlaminar fracture. In particular we will be looking at deformations in the resin rich region between the layers of the laminate as they are pulled or sheared apart by external loads. We will also develop an approach for measuring the initiation and growth of voids in the resin using small angle x-ray scattering (SAXS) which we will perform at the Cornell High Energy Synchrotron Source (CHESS). Both projects will require significant development of experimental protocols, apparatus and data reduction. As such they would serve as excellent training grounds for students interested in engineering materials who wish to have an opportunity to apply and improve their design and analytical skills. Two students are sought for the project.
Prof. Alan T. Zehnder, atz2@cornell.edu