Self healing Materials

a presentation of self-healing materials..
a major chunk of information is from the presentation of Ian Bond, University Of Bristol

1. Self-Healing Materials SAHIL GUPTA P2008CS1030 RAGHAV PAUL P2008ME1122

2. Why self-healing? Approaches to self-healing Microsphere embedment 3D Micro-vascular embedment Electro-hydrodynamics Possible Applications & Future scope Concluding remarks Self Healing Materials

3. Traditional repairs are expensive! to design (never two the same) to implement (removal from service or in-situ repair) to certify & monitor (additional inspection often required) throughout remaining operational life. Sense and respond to damage,restore performance without affecting inherent properties. KEY ! - N o human intervention required. Provide early means of detection of damage It is like modeling and mimicking of the human body and other living systems which have the ability to self heal. Why self-healing?

4. A microencapsulated healing agent is embedded in a composite matrix containing a catalyst capable of polymerizing the healing agent. Cracks form in the matrix wherever damage occurs. The crack ruptures the microcapsules, releasing the healing agent into the crack plane through capillary action. The healing agent contacts the catalyst triggering polymerization that bonds the crack faces closed. iv. Also possible at nano scale Microsphere Embedment SEM image of broken microsphere

5. Materials used There are several constituent materials which, when combined function as self healing material system: Healing Agent: Dicyclopentadiene (DCPD) Microcapsule shell: Urea–formaldehyde (UF) (mean 166µm diameter) Chemical Catalyst: Bis ( tricyclohexylphosphine ) bensylidine ruthenium (IV) Flexiblizer : Heloxy 71, Shell Chemical Company used to improve toughness and crack growth stability. Polymer Matrix: Epoxy Polymer Matrix EPON 828 Fiber Reinforcement: Carbon Fiber (Plain weave fabric constructed with 3K towns)

6. Re-healing capable materials Material could use a system of veins to distribute healing agent intelligently The bio-inspired design delivers healing agent to cracks in a polymer coating via a three-dimensional micro-vascular network embedded in the material. Crack damage is thus healed repeatedly. This can also ensure continuous delivery of healing agents for self-repair from a additional reservoir 3D Microvascular structure embedment

7. Electrohydrodynamics NiSO 4 can be electrochemically dispersed into the small voids present in the system. Voltage applied across inner and outer surfaces. Damage causes an increase in current density at the location of the damage Increased current density causes particle coagulation at damage site

8. Shape Memory Alloys Shape memory alloys such as Nitinol (a Nickel-Titanium alloy) exhibit the self healing effect when heated Before heating the material tends to have low yield strength After heating to a certain temperature the material returns to the original state In returning to the original state, large forces can be generated

9. Anything that cannot be reached for repair at the moment of damage! Civil Structures (Engineered cementitious composite) Tools (Nitinol ) Space applications Self healing coatings for steel structure Composite materials for: Aerospace applications High quality sporting equipment Microelectronics Medical uses: To detect a breach in a glove, gown, etc., using electrohydrodynamic technology Potential Applications of Self Healing Materials

10. Case study Self-healing materials and use thereof for extending the lifespan of a tyre Self-Repairing Aircraft Could Revolutionize Aviation Safety The Maximum strength recoverable til date is about 75-80% Catalyst, and microsphere ‘clustering’ causes less polymerization Manufacturing of material is very difficult and expensive More research is required before real world applications are exercised Results & Shortcomings