Seminar Series - 2001-2002

Static and Fatigue Fracture of Graphite-Epoxy Composites with PAN Nanofiber Reinforcement at Interfaces

Emrah Gokdag
M.S. Thesis Defense
Department of Engineering Mechanics
University of Nebraska - Lincoln
Advisor:  Dr. Yuris Dzenis

Date: Tuesday, December 11, 2001
Time: 3:30 p.m.
Place: W183 Nebraska Hall


Advanced composites are extensively used in high technology applications such as aerospace and defense structures because of their high modulus and strength, good fatigue durability, and excellent corrosion resistance. However, delamination often limits their applications as this damage mode causes serious reduction in stiffness and can lead to catastrophic failure. There are different approaches to suppress delamination and to improve interlaminar fracture toughness of composites. One of them, pursued in our group, involves toughening the interfaces with polymer nanofibers. The objective of this work was experimental analysis of laminated composites with interfaces reinforced with thermoplastic nanofibers. Static and fatigue behavior of graphite-epoxy composites with PAN nanofiber reinforcement at interfaces was studied. Interlaminar Mode I and Mode II fracture of composites with nanoreinforced layers of various thickness was studied under static and fatigue loading conditions. Double cantilever beam (DCB) and end notched flexure (ENF) tests were performed to evaluate Mode I and Mode II fracture toughness, respectively. Different data reduction methods were compared and used for calculation of Mode I and Mode II energy release rates. Laser profilometry and scanning electron microscopy (SEM) were used for topographical analysis of fracture surfaces. Acoustic emission (AE) analysis was performed for composite damage evaluation under fatigue. The results obtained demonstrated substantial improvements in both static and fatigue interlaminar fracture resistance of composites with nanoreinforced interfaces.


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