2.2.1.2 Self-Healing Materials for Tip Region Cracks2.2.1.2 Self-Healing Materials for Tip Region Cracks

Science & Technology Objective(s):• Identify one or more self-healing materials that have

potential for gas turbine component construction• Demonstrate the ability of an emerging self-healing

material for fan and/or compressor airfoils

Photograph of spin Pit & Rub Shoe

2.2.1 Advanced Materials2.2.1 Advanced Materials

Dunn & Mills (Ohio State) & Adams (Case Western)

Collaborations:• Government - NASA Glenn and U.S.Air Force• URETI - Ohio State, Case Western• Industry - GEAE, Rolls-Royce America, and P/W• Synergism with existing programs - GEAE blade tip

rub program at OSU

Proposed Approach:• Identify potential “smart materials” for airfoil and

casing • Extend “smart material” temperature range • Incorporate entrained pockets of metal with good

wetting properties

NASA Relevance/Impact:• Significant reduction in potential tip losses because

of damaged airfoils• Cost savings because airfoil replacement

advantages• Crack reduction should reduce blade-out potential

Milestones/Accomplishments:• Selection of potential materials• Incorporation of entrained pockets of metal in

material• Demonstration of high temperature and strength

capability of material selected• Develop model for tip/casing rub dynamics• Verify model with realistic measurements• Tip rub measurement program @ engine speed

2.2.1.2 Background2.2.1.2 Background

• Tip Rubs for Fans and Compressors are not Preventable– Airfoil material and rub shoe material influence

what will happen to airfoil– Tiny cracks can and do develop as a result of

these rubs and propagate into the airfoil– Potentially result in loss of a portion or all of airfoil

• Emerging “Smart Materials” Offer Potential for Helping to Mitigate Crack Problem

• Crack Needs to “heal Instantaneously” for Material to be Useful

2.2.1.2 Proposed Approach2.2.1.2 Proposed Approach

• Select Potential “Smart Material” that may Work for this Purpose, i.e. entrained Mg forming MgO – Material should be capable of operating at high stress/strain load @

elevated temperature

– Material will also need to be capable of operating with entrained pockets of metal for “healing” purposes

• Develop Analytical Model to Describe Interaction Between Selected Material and Potential Casing Coating Materials– Demonstrate that model works for known cases of tip/casing rub

• Perform Measurement Program @ Engine Speed to Demonstrate “self healing” Capability of Material Selected