Fracture and fatigue of a self-healing polymer composite material

Polymers are susceptible to damage in the form of cracks, which form deep within the structure where detection is difficult and repair is often impossible. For applications ranging from structural composites to microelectronics, once cracks have formed within polymeric materials, the integrity of the structure is significantly compromised. A novel approach is explored for improving the life of thermosetting polymers through the addition of self-healing functionality.; A fracture-based protocol is established for characterizing healing efficiency of the self-healing epoxy. The fracture toughness is measured using a tapered double-cantilever beam (TDCB) specimen. Healing efficiency of over 90% is obtained for 5 wt% 180 μm diameter microcapsules and 2.5 wt% catalyst. Fracture of the neat epoxy is brittle, exhibiting a mirror fracture surface. Addition of dicyclopentadiene-filled urea-formaldehyde microcapsules yields up to 127% increase in fracture toughness and induces a change in the fracture plane morphology.; A comprehensive experimental program is performed to assess the fatigue behavior of a self-healing polymer. The inherent fatigue characteristics of the material are measured. A fatigue-life-extension-based protocol is established for characterizing self-healing under a cyclic loading. Retardation and arrest of the fatigue crack result from self-healing induced crack-tip shielding mechanisms and significantly increase fatigue life.