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Development of High Toughness Bioactive Composites Using Electrospinning Techniques

Baji, Avinash

Abstract Details

2008, Doctor of Philosophy, University of Akron, Mechanical Engineering.

Little is understood on mechanisms used by nature in designing materials with high strength and toughness from weaker constituents. Nanostructured materials found in nature such as bones, nacre and teeth are composites of proteins and bio-minerals and are found to possess superior mechanical properties in comparison to its constituent phases. These composites are found to have protein molecules confined between the layers of the ceramic platelets. This kind of hierarchical arrangement of organic-inorganic nano-particles at the structural level provides superior strength and toughness to the composite. The mechanisms used by these materials help in providing the guidelines for the design of biomimetic materials with optimized strength and toughness.

Electrospinning method is used in this study to produce polymer fibers with diameters in the range of nanometers to a few hundred micrometers. The mechanical properties of the hydroxyapatite (HAP) reinforced poly(ε-caprolactone) (PCL) composite samples (non-spun samples) and electrospun fibers are evaluated. The toughness properties of the non-spun and spun samples are quantified using the concept of essential work of fracture (EWF) techniques. The electrospun system showed a substantial increase in plane-stress essential work of fracture in comparison to bulk specimens processed from pellets. Toughness decreased as HAP loading increased. Mechanical properties including tensile strength and modulus are found to increase with HAP concentration in general. The tensile properties of single electrospun fibers have not been widely investigated due to the difficulties in handling nanofibers and measuring low load for deformation. This study addresses the tensile properties of electrospun fibers in detail using a nanoforce tensile tester and the effect of dimensional confinement on free standing biodegradable poly(ε-caprolactone) (PCL) are investigated using electrospinning- enabled techniques. The structural properties such as crystallinity and molecular orientation of the spun fibers are examined using wide angle X-ray diffraction (WAXD). The degree of crystallinity and molecular orientation of fibers are enhanced when the diameter of spun fibers is reduced, resulting in improved mechanical strength and stiffness. It is evident that PCL fibers with decreasing fiber diameter exhibit an abrupt shift in tensile performance in comparison to those derived from non-spun systems. The abrupt shift in tensile strength and stiffness of electrospun PCL fibers occurs at around 700 nm in diameter and illustrates the importance of studying the mechanical behavior of the nanofibers, for the first time, systematically with the aid from electrospinning techniques.

Shing-Chung Wong, PhD (Advisor)
211 p.

Recommended Citations

Citations

  • Baji, A. (2008). Development of High Toughness Bioactive Composites Using Electrospinning Techniques [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1222895930

    APA Style (7th edition)

  • Baji, Avinash. Development of High Toughness Bioactive Composites Using Electrospinning Techniques. 2008. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1222895930.

    MLA Style (8th edition)

  • Baji, Avinash. "Development of High Toughness Bioactive Composites Using Electrospinning Techniques." Doctoral dissertation, University of Akron, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1222895930

    Chicago Manual of Style (17th edition)