Use of Magnetostrictive Sensor Use of Magnetostrictive Sensor Monitoring Technology (Monitoring Technology (MsSMTMsSMT) for the ) for the Evaluation of Adhesively Bonded PatchEvaluation of Adhesively Bonded Patch

(Patent Pending)(Patent Pending)

Glenn Light, Ph.D.Glenn Light, Ph.D.Hegeon Kwun, Ph.D.Hegeon Kwun, Ph.D.

Sang Kim, Ph.D.Sang Kim, Ph.D.Robert SpinksRobert Spinks

Southwest Research InstituteSouthwest Research InstituteSan Antonio, TXSan Antonio, TX

Discussion of ProblemDiscussion of Problem

Defects in aircraft structure can sometimes be repaired using adhesively bonded patch

Once the bonded patch repair has been completed, it is necessary to inspect the region to– Verify that the defect is not growing

– Verify the quality of the patch

Technical ApproachTechnical Approach

Bond MsSM probe unit onto the aircraft structureCollect reference waveform (has data from the bonded region as well as the defect)Process collected data to determine changes in – Bond quality– Defect size

Laboratory Experiments of MsSM with Bonded Patch and Defect in Aluminum Plate

0.125-inch-thick,3 x 1 ft Aluminum Plate

1/16-inch-thick,8 x 4 inch Aluminum Patch

51-percent-thickness-deep,2-inch-long Notch Defect

MsS Probe

Aluminum with Patch Bonded over 51-Percent-Thickness-Deep, 2-Inch-Long Notch Defect

Initialpulse

Front Patch

Back Patch

Plate End

Notch

Aluminum with Patch Bonded and Defect Growing

Initialpulse

Before Placing a Notch

After Placing a 51%-thickness-deep Notch

1-inch-long

0.5-inch-long

1.5-inch-long

2-inch-long

After Applying Waveform Differential Algorithmin Time Domain to Monitor Notch Growth

Initialpulse

Before Placing a Notch

After Placing a 51%-thickness-deep Notch

Front PatchBack Patch

Plate End

1-inch-long

0.5-inch-long

1.5-inch-long

2-inch-long

Aluminum with Patch and Defect with Changes in the Bond Quality

Initialpulse

Patch with good bond

Patch with Partial Front Debond

Notch

Patch with Partial Front + Partial Back Debond

Patch with Total Front + Partial Back Debond

Complete Patch Debond

After Applying Waveform Differential Algorithmin Time Domain to Monitor Patch Bond

Initialpulse

Plate End

Notch

Patch with good bond

Patch with Partial Front Debond

Patch with Partial Front + Partial Back Debond

Patch with Total Front + Partial Back Debond

Complete Patch Debond

Relative Velocity Change of Guided Wave in Patch Region with Changes in the Bond Quality

Bon

ded

Patc

h

Deb

onde

d Pa

tchChanges in the Bond Quality

GoodBond

PartialFront debond

Partial Front+

PartialBack

Debond

TotalFront +

PartialBack

Debond

CompletePatch

Debond

ResultsResultsSouthwest Research Institute applied the MsSM to monitor the quality of adhesively bonded patch and the notch growing under the patch.

(1) Waveform differential algorithm was developed that allows the detection of a notch growing and bond-quality change in sequential MsS signals.

(2) Change of the bond quality in patch region could be identifiable using relative velocity change of guided wave.

Future Work to be Conducted on Future Work to be Conducted on MsSM MsSM with Bonded Nickel MsS Probewith Bonded Nickel MsS Probe

Laboratory evaluation on honeycomb composite structuresLaboratory evaluation on graphite epoxy patchesPreliminary development of flat sensor coil that could be read out by a remote sensorField demonstration of MsSM with bonded nickel MsS probe on aircraft structureInvestigation of variations in magnetic property of nickel MsS probe as a result of the aerospace environment