Piezoelectric sensors would significantly reduce the cost of damage detection

MAIN ACHIEVEMENT:

Piezoelectric sensors produce Lamb waves that can be used to identify damages at a lower cost in the increasingly common carbon fiber composites.

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Damage Detection in Carbon Fiber Composite Materials Using Lamb Waves: FFT vs. PCA

Sensor 1 Sensor 2

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Joshua Hardisty Dr. Arda Vanli Spandan Sharma High Performance Materials Institute – Florida State University

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PCA Damage Index vs. Damage Severity

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FFT Chang (2011) Lecture Notes

• 10 x 27 in. carbon fiber composite plate

• Damages were introduced at varying distances (3 in. – 21 in.) and with different severity (1/8 in. – ½ in. hole)

• Lamb waves were sent through the plate by two sensors located at the ends of the plate

Signal and its Fast Fourier Transform due to a 13/32” hole at 3” away from Sensor 1

Fast Fourier Transform (FFT) Method

• The time domain signal is converted to a frequency domain signal • The frequency domain signal can be integrated to find the energy of the signal

Fast Fourier Transform (FFT) vs. Principle Component Analysis (PCA) • A comparison of the slopes of the FFT and PCA methods of analysis show that for every increase in damage size, there is a much larger drop in factor score/area • The PCA is much more sensitive

Principal Component Analysis (PCA) Method

• PCA is a method used to reduce the number of dimensions in an experiment • Principal components are found by projecting the data onto the principal axes of the covariance matrix

y = -7.9234x + 8.4317

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Area FFT Score vs. Damage distance

y = -36.449x + 16.068

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Factor Score PCA vs. Damage distance

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• Structural Health Monitoring in the aerospace industry is worth over $9 billion. • Piezoelectric sensors in combination with the PCA method could reduce the cost of damage detection by 50%.

To be able to accurately detect damages.

•Build a model to characterize the location and severity of damages in carbon fiber composites

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Example: What is the distance of a 13/32 in. damage from sensor 1 with a DI percentage difference of 45%? Solve for x using the equation from the PCA DI vs. Distance graph with y = 45%: The answer should be about 5 in.

Carbon Fiber Composite Board

Piezoelectric Sensor

y = 0.01x4 - 0.72x3 + 14.99x2 - 131.56x + 418.71

R² = 1.00

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Distance from Sensor

PCA Damage Index vs. Distance

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y = 219.19x2 - 65.65x + 16.18 R² = 0.99

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PCA Damage Index vs. Damage Severity

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Sensors on airplane wing

Future Inquiries with Principle Component Analysis (PCA) • “Tail” of the PCA vs. Distance graph increases when a decrease is expected • How sensitive is the measurement (How small are the damages this method can detect)?

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Aviation Week "10-year Forecast" April 2011 – Market Value

Heavy Maintenance and Modifications

Line Maintenance

Airbus 30%

Boeing 61%

Other 9%

Fleet Distribution By Manufacturer - 2009

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How does Principal Component Analysis add value? • Fewer sensors result in lower fixed and installation costs

Why use piezoelectric sensors? • By using smarter sensor systems, maintenance time can be cut by over 40% • Most maintenance costs come from aircraft “down time” • Cutting maintenance time costs directly cuts total costs

Possible Manufacturers

International Air Transport Association