Self-Healing Materials

SAHIL GUPTAP2008CS1030

RAGHAV PAUL P2008ME1122

Why self-healing? Approaches to self-healingMicrosphere embedment3D Micro-vascular embedmentElectro-hydrodynamics

Possible Applications & Future scope Concluding remarks

Self Healing Materials

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! - No 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?

A microencapsulated healing agent is embedded in a composite matrix containing a catalyst capable of polymerizing the healing agent.

i. Cracks form in the matrix wherever damage occurs.

ii. The crack ruptures the microcapsules, releasing the healing agent into the crack plane through capillary action.

iii. 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

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)

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

Electrohydrodynamics

NiSO4 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

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

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

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