Master of Science in Mechanical Engineering (MSME)


Mechanical Engineering

Document Type



The study of self-healing materials is inspired by biological systems in which damage triggers an autonomous healing response. In recent years, this concept of autonomic healing material, where initiation of repair is integral to the material, is being considered for engineering applications. The concept offers the designer an ability to incorporate secondary functional ability of counteracting service degradation in addition to achieving the primary, usually structural integrity, requirement. Self-healing materials also have the benefit of offering lighter and optimized structures as well as reduced maintenance cost. Previous works on polymer matrix composites have shown that significant fractions of mechanical properties can be restored through self-healing in damaged materials. The self-healing composite material developed in this study is a fiber-reinforced polymer matrix composite. The study has three major categories of self-healing composite systems. In the initial study, a single fiber polymer matrix self-healing composite system is developed and analyzed. In the latter stage of the study, multiple commercial glass fibers are used as a reinforcing material in the self-healing system. The inclusion of functionalized carbon nanotubes in the healing medium to further enhance the healing process is considered at the final stage of the study. The self-healing approach utilizes a releasable healing agent contained in a hollow fiber that is embedded in a resin system. Specimens are produced using a hollow glass fiber and epoxy resin. In addition, in the case of multiple fibers test, e-glass fibers are incorporated in the composite. When a crack is initiated and propagates through the composite breaking the hollow fiber, a liquid healing agent comes out and fills the crack gap. Polymerization of the monomer healing agent is facilitated when it contacts a catalyst that is pre-coated on the outside surface of the hollow glass fiber. Healed, damaged and virgin specimens are tested in tension for all the different sets of composites investigated. The results demonstrate that a considerable portion of the tensile strength is recovered by the self-healing functionality of both the single fiber and fiber-reinforced polymer composites. A major advantage of this research is the fact that the healing is found to be localized allowing further multiple healing of the composite in the presence of several cracks. Incorporation of functionalized carbon nanotubes in the healing medium has provided additional efficiency in the composites compared to those without carbon nanotubes.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Woldesenbet ,Eyassu