12/04/2011: Biomimetic materials for self healing and active cooling applications


Biomimetic materials for self healing and active cooling applications:
experimental observations and multiscale modeling

April 12, 2011, 13:00 -14:00, CAB H52, ETH Zurich

Philippe H. Geubelle
Professor and Associate Head, Department of Aerospace Engineering and Beckman Institute, University of Illinois at Urbana-Champaign

 

Self-healing composites are a new class of biomimetic polymeric materials that present the unique ability to heal slowly propagating cracks in an autonomic fashion. Of particular interest in a room-temperature-cured epoxy matrix containing a dicyclopentadiene (DCPD) healing agent encapsulated in 20 to 200 micron-size micro-capsules and a pre-dispersed catalyst. As a crack approaches a micro-capsule, the stress concentration present in the vicinity of its tip breaks the capsule wall, releasing the healing agent that polymerizes in contact with the catalyst and heals the crack.

This presentation will focus on key experimental and analytical results on the fatigue response of the self-healing composite, where substantial healing has been demonstrated for low and medium loading levels. On the modeling side, a cure-dependent cohesive model has been developed to capture the competition between fatigue crack advance and healing kinetics. The model incorporates the two key effects of the healing agent on the near-tip fields, i.e., the crack closure (or wedging) effect of the DCPD present in the wake of the advancing crack front during the unloading phase of the loading cycle, and the adhesive effect of the polymerized healing agent that resists the opening of the crack faces during the reloading phase. The talk will also present a multiscale cohesive finite element framework developed to model the application of this self-healing concept to epoxy-based adhesive systems. The multiscale framework allows relating the failure processes taking place in the adhesive layer to the corresponding macroscopic cohesive traction-separation law used to model the failure of the bonded structure.

The talk will end with a brief discussion of on-going work in the computational design of another class of biomimetic polymeric materials composed of a microvascular network embedded in a polymeric matrix or in a fiber-reinforced composite, with emphasis on the cooling application.