Vinod B. Suryawanshi – Ph.D. Dissertation Defense 6/17/2016 at 2:00 P.M.

JSNN – Vinod B. Suryawanshi – Ph.D. Dissertation Defense

Candidate: Vinod B. Suryawanshi

Advisor: Dr. Ajit Kelkar

Department: Nanoengineering

Date: Friday, June 17, 2016

Time: 2:00 P.M. – 3:30 P.M.

Location: JSNN Room 209

2907 E. Gate City Blvd., Greensboro, NC 27401

Title: “Fracture and Fatigue Behavior of Electrospun Nanofibers Reinforced Composites.”

Abstract:

Polymeric composite materials are widely used for primary load carrying structures in aerospace, automotive, energy and sports applications. Structural performance of these materials depends on fracture and fatigue behavior under different loading conditions. In recent times, nanomaterials due to their superior mechanical properties are extensively researched as potential secondary reinforcement in composite materials. Electrospun SiO2 nanofibers have shown some promising results on improvement of mechanical properties of composites material. However, limited work is done on understanding fracture behavior and no studies are reported on fatigue behavior of SiO2 nanofibers reinforced composites.

It is well known that fiber-matrix adhesion plays an important role on mechanical properties of composite materials. In this research, an effect of silane treatment of electrospun nanofibers mat on mode I fracture behavior of vacuum bagging manufactured  nanofibers interleaved glass/epoxy composites is investigated. Also, it is reported in the literature that, poor wetting of nanofibers is detrimental to the fracture behavior of nanofibers interleaved composites. To resolve the issue, nanofibers were pre-wetted prior to interleaving in fabric layup. The results showed that pre-wetting of nanofibers mat improves the mode I fracture behavior significantly.

In the literature, number of studies reported the effect of inclusion of nanomaterials on static performance of the composite materials; however, limited work is done on characterization of fatigue behavior. During this research, effect of SiO2 nanofibers reinforcement on flexural fatigue behavior of composites is investigated. It is observed that nanomodification improves the flexural fatigue life by 77 ± 22 %.

Fatigue loading of composites results in damage and ultimately the failure of the composites, an accurate prediction of fatigue life and damage is crucial for maintenance and repair of these structures during its service life. In this research, sigmoidal function is used to model the fatigue life and stiffness degradation during the flexural fatigue of composite laminate. The results of simulation agreed very well with the experimental results.

Finally, a three-dimensional finite element model is developed to simulate the progressive failure of composite under flexural loading. The results obtained by 3-D finite element model agreed well with the experimental results.