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Lamb Waves for Composite Health Monitoring Non-Destructive Testing – Laurens Stevaert 2Ma Chemical & Materials Engineering – VUB/ULB 2012-13 1.

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Presentation on theme: "Lamb Waves for Composite Health Monitoring Non-Destructive Testing – Laurens Stevaert 2Ma Chemical & Materials Engineering – VUB/ULB 2012-13 1."— Presentation transcript:

1 Lamb Waves for Composite Health Monitoring Non-Destructive Testing – Laurens Stevaert 2Ma Chemical & Materials Engineering – VUB/ULB

2 COMPOSITES Properties, (Dis)Advantages & Inspection 2

3 Composites: Properties Widely used Aerospace Automotive Naval Advantages High specific strength Light weight Fatigue and corrosion resistance Design freedom – tailored properties 3

4 Composites: Properties Disadvantage: impact damage Low through-thickness strength Even low velocity! Bird strike Tool dropped during servicing Runway stones Damage Indentation Delamination Fibre/matrix cracking Barely Visible Impact Damage Detect, locate & characterize damage! 4

5 Composites: N-D Inspection Loads of methods Visual inspection Optical methods Eddy current (E-M waves) Thermography (input heat energy) Ultrasonic (high E acoustic waves) Etc. But… Cost & time Bulky transducers Part has to be removed, sometimes placed under water Point scan 5

6 LAMB WAVES Properties & Application 6

7 Guided Wave Testing High detection range 100m wikipedia.org Mechanical stress waves Guided by geometry Super low freq. ( kHz) Other advantages: Elastic waves: reversible deform. mech. properties Through thickness scanning Imaging internal hidden defects 7

8 Lamb Waves: Properties 8

9 Lamb Waves: Testing Normally: transducers on the outside Good coupling required! Contact mode Air is not a good medium Immersion in water part has to be removed… Water jets very sensitive… Non-contact mode Easier option for testing Often expensive 9

10 Lamb Waves: Smart Systems Small transducers permanently attached To the surface Embedded in composite laminate Constantly monitor the structure, on demand info Piezoelectric Wafer Transducers Transmitter: electrical E mechanical E (elastic waves) Receiver: mechanical E (propagated wave) electrical E E.g.: PZT – Lead Zirconate Titanate 10 eetimes.com

11 Lamb Waves: Analysis 11

12 FUTURE WORK Weak points & Improvements 12

13 Future Work Some disadvantages Single mode: dispersion properties needed difficult for composites! Low frequency = large wavelengths small defects not correctly measured Analysis over long time influenced by T, loading, bad coupling… Anisotropy 13 Commercial applications limited… for now

14 Conclusion Lamb waves Special properties Propagate through plate geometries Detection over large distances Smart systems Active structural health monitoring Monitor damage (evolution) While in-service! 14 Promising technique!

15 QUESTIONS? Lamb Wave – Vague de Agneau? 15

16 Sources Diamanti, K. et al (2010) Structural Health Monitoring Techniques for Aircraft Composite Structures. Progress in Aerospace Sciences, Vol 46, pp. 342 – 352 Staszewski, W.J. et al (2008) Health Monitoring of Aerospace Composite Structures – Active and Passive Approach. Composites Science and Technology, Vol 69, pp – 1685 Castaings, M. et al (2011) Sizing of Impact Damages in Composite Materials Using Ultrasonic Guided Waves. NDT&E International, Vol 46, pp. 22 – 31 16


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