Composite NDT and SHM for Spacecraft and Aircraft, Using MWM-Arrays

Transcription

1 2012 Aircraft Airworthiness & Sustainment (AA&S) Conference Baltimore, MD, April 2-5, 2012 Composite NDT and SHM for Spacecraft and Aircraft, Using MWM-Arrays Neil Goldfine, Andrew Washabaugh, David Jablonski, Zachary Thomas, and Christopher Martin JENTEK Sensors, Inc Clematis Avenue, Waltham MA Phone: ; April 5, 2012 MWM sensors and MWM-Arrays covered by issued and pending patents, including, but not limited to: 8,050,883; 7,994,781; 7,876,094; 7,812,601; 7,188,532; 7,183,764; 7,161,351; 7,161,350; 7,106,055; 7,095,224; 7,049,811; 6,995,557; 6,992,482; 6,952,095; 6,798,198; 6,784,662; 6,781,387; 6,727,691; 6,657,429; 6,486,673; 6,420,876; 6,380,747; 6,377,039; 6,351,120; 6,198,279; 6,188,218; 6,144,206; 5,966,011; 5,793,206; RE39,206 E. Airworthiness 2012 Slide 1

2 Goals, Technical Approach and Funding Goal is to develop: - High resolution damage and condition imaging for carbon fiber composite NDT - Volumetric stress sensing magnetic stress gages for composites The MWM-Array is a linear drive eddy current sensor array construct - Can induce eddy currents in the linear fibers of carbon fiber composites - Use winding geometry changes to alter penetration depth and characterize damage Detection/characterization of impact and other damage and monitoring of strain/stress as a function of depth and fiber orientation is accomplished by modeling the fiber properties/orientation/density/contact. Simplified models are being used now with advanced models still under development. Funding - NASA for micromechanical model development and application to composite overwrapped pressure vessels (COPVs) - Army for rotorblade NDT - Navy for NDT of aircraft composites Airworthiness 2012 Slide 2

3 Linear Drive Eddy Current Sensors MWM and MWM -Arrays FA28 MWM-Array FA24 MWM-Array (similar to FA26) Parallel Architecture Instruments: GS-Durable and GS-HandHeld Airworthiness 2012 Slide 3

4 Micromechanical Model: Eddy Current Extension (Model under development in NASA Phase II SBIR) Linear drive MWM-Array sensing of composite with conducting fibers and insulating matrix Model uses a composite cylinder assemblage Solve for field around a single fiber and extend to fiber bundle Effective complex permeability and conductivity depend upon orientation with respect to fiber axis, fiber density and fiber contact Focus on Carbon Fiber/Epoxy composites perp 0 par f v f * * par perp o perp Fiber par perp perp par perp Radius a Airworthiness 2012 Slide 4

5 Uniaxial/Biaxial Specimens: Orientation Varied Single element MWM sensor; 10 MHz Air/shunt calibration Sensor response highly directional Highest response when fibers when sensor drive oriented parallel to fibers For the uniaxial specimen, both the magnitude and phase of the sensor response are significant every 180º Uniaxial specimens Signal Variation During Rotational Scan FS33 drive perpendicular to uniaxial fibers Biaxial ( 45 ) specimens +45º fibers -45º fibers Graphite fiber epoxy composite samples provided by Boeing Uniaxial fibers Airworthiness 2012 Slide 5

6 Measurement Grids for Simplified Model Example Grids for the MWM FS35 Sensor and Aluminum 10 khz 1 MHz Airworthiness 2012 Slide 6

7 MWM Sensor Selection Magnetic field decays exponentially with distance away from sensor Decay rate determined by skin depth at high freq. and sensor dimensions at low frequency High frequencies needed to induce significant eddy currents Large dimensions needed for thick composites FA24/FA26 (based on drive width) 3 2 Skin depth: 1 f Penetration Depth (mm) FA24/FA26 (based on sense position) FA28 MWM-Array increasing Electrical Conductivity (ks/m) Penetration Depth (mils) Frequency (Hz) 4 Airworthiness 2012 Slide 7

8 Quasi-isotropic Composite Panel Stackup Stackup for bending test panel Uniaxial properties for each layer MWM-Array sensitive to composite layers with fibers oriented parallel to drive windings Composite layer considered insulating if fibers NOT within 5º of sensor orientation This visualization indicates that each sensor orientation is only sensitive to a subset of plies at varying depths within the composite. MWM-Array h eff MWM-Array h MWM-Array h 0º orientation 45º orientation 90º orientation -45º orientation MWM-Array h MWM-Array h eff eff 0 DEGREES 45 DEGREES 90 DEGREES -45 DEGREES Airworthiness 2012 Slide 8

9 Simplified Grids for Quasi-isotropic Stackup Grid size illustrates the effect of fiber orientation and distance from the sensor FS33-45º 90º 45º FS36/BD-MSG -45º 90º Increasing Lift-off Std halfspace 0º Std halfspace Increasing Lift-off 45º 0º Increasing Conductivity Increasing Conductivity The plots compare standard infinite half space grid to parameterized grids for each sensor orientation Sensitivity to a subset of plies causes a shift in effective property estimates compared to standard grids Smaller effective conductivities; effective lift-off can be high, lower, even negative, depending upon orientation Airworthiness 2012 Slide 9

10 Example COPV Stackup Stackup for COPV and COPV ring specimen MWM-Array sensitive to composite layers with fibers oriented parallel to drive windings This indicates that the sensor orientation is important for assessing the fiber properties. non-fiber orientation ±17º or ±18º orientation ±90º orientation ±60º orientation Al liner Al liner /2 eff Al liner Al liner /2 /2 h /2 h h h MWM-Array MWM-Array MWM-Array MWM-Array Airworthiness 2012 Slide 10

11 JENTEK Grids for MWM-Array on COPV Samples Representative grids for a composite overwrapped pressure vessel (COPV) Models account for layered geometry and orientation effects on properties within each layer FA28 FA24 Air Air Increasing Lift-off Std halfspace Increasing Conductivity 90º 72º 22º Increasing Lift-off Increasing Conductivity Std halfspace 90º 72º 22º Airworthiness 2012 Slide 11

12 Segmented Field Magnetometry Different sensor geometries provide different penetration depths Segmented field sensors such as FA41 can provide two depths in a single scan Depth of sensitivity variation needed to characterize damage variation with depth Frequency variation alone is not sufficient MWM-Array h FS33/FA28 FA41 (near) FS36/BD-MSG FA 41 (far)/ FA24/FA26 Penetration Depth (mm) MWM-Array (based on sense position) FA24/FA26 FA41 (far) FS36/BD-MSG FA41 (near) FA28 FS33 Electrical Conductivity (ks/m) Penetration Depth (mils) Frequency (Hz) Skin depth: 1 f Airworthiness 2012 Slide 12

13 Approach to Volumetric Imaging Combination of sensor orientation and geometry can help isolate depth and region of damage: (i) sensor orientation determines plies, (ii) sensor geometry determines depth of sensitivity, (iii) spatial extent of damage determined from scan image FA28 0º MWM-Array h FA28 90º FA26, 90º FA26 0º Damage region FA26 90º Airworthiness 2012 Slide 13

14 Volumetric Imaging of Composite Impact Damage Sample provided courtesy of Lockheed Martin Representative MWM-Array Scan Image Airworthiness 2012 Slide 14

15 Representative Quasi-isotropic Panel Scan Images Before Impact After Impact Subtracted Subtracted and Smoothed 15.8 MHz 10 MHz 5 MHz Airworthiness 2012 Slide 15

16 Summary Image Individual scans combined together to create composite cross-sectional view Airworthiness 2012 Slide 16

17 Cross Sectional Images: Panel 1, Low Impact Level MWM-Array FA28 Data Cross Sectional View along X-axis Cross Sectional View along Y-axis Airworthiness 2012 Slide 17

18 Cross Sectional Images: Panel 2, Medium Impact Level MWM-Array FA28 Data Cross Sectional View along X-axis Cross Sectional View along Y-axis Airworthiness 2012 Slide 18

19 Cross Sectional Images: Panel 3, High Impact Level MWM-Array FA28 Data Cross Sectional View along X-axis Cross Sectional View along Y-axis Airworthiness 2012 Slide 19

20 COPV Testing 37-Channel Probe 7 Sensor TEST SETUP Rotary Table and Encoder SCI AC-5251 S/N 005 SCI AC-5250 S/N cal gunfire test bottle SCI AC-5128A S/N 166 See complimentary presentation: Continued Development of Meandering Winding Magnetometer (MWM ) Eddy Current Sensors for the Health Monitoring, Modeling and Damage Detection of Composite Materials Session: IVHM - Structural Health Monitoring for Damage Detection Presentation time: Thursday, April 05, :30 PM Airworthiness 2012 Slide 20

21 Rotation Scan of Vessels AC-5250 S/N:030 FA28 MWM-Array Scan Manufacturer Fiber Layup FA28 Shallow /4 = 37 mils Fiber orientation Material Carbon fiber composite Carbon fiber composite Carbon fiber composite Carbon fiber composite Carbon fiber composite Glass fiber composite FA24 MWM-Array Scan FA24 Deeper /4 = 130 mils Airworthiness 2012 Slide 21

22 MWM-Array Low Freq. Lift-Off Scans on COPV Lift-Off image shows liner damage; freq khz Before Impact Damage After Impact Damage Baseline Subtracted Preliminary Filtering angular 30 ft-lbs ~46 mils 20 ft-lbs ~26 mils 15 ft-lbs ~22 mils 10 ft-lbs ~6 mils axial Sample AC ; 90 Sensor drive orientation Higher impact energy results in larger dents in the aluminum liner Sensor: MWM-Array FA24 Airworthiness 2012 Slide 22

23 Periodic Response to Woven Plies FA28 scanned over a Gr/Ep composite with a coarse woven fabric ply near the surface The spatially periodic sensor response is consistent with the woven fabric tow width Distance between peaks ~0.09-in. This corresponds to 11 oscillations/in. Power spectrum density plot indicates strong spatial frequency near 11/in. Magnitude of 1 channel with photograph of specimen Airworthiness 2012 Slide 23

24 MWM Response to Stress in 4pt Bending Unidirectional Carbon Fiber Composite FA28 Tension FA28 FA28 Compression Conductivity (%IACS) As presented at NASA Sensors Tech Forum Boston, MA; October 10-12, 2011 Airworthiness 2012 Slide 24 Microstrain

25 Surface-Mounted Sensor Damage Monitoring MWM-Array FA24 Tests run under NAVAIR SBIR at Lockheed Martin Aeronautics, Ft. Worth, TX Airworthiness 2012 Slide 25

26 Review: Goals, Technical Approach and Funding Goal is to develop: - High resolution damage and condition imaging for carbon fiber composite NDT - Volumetric stress sensing magnetic stress gages for composites The MWM-Array is a linear drive eddy current sensor array construct - Can induce eddy currents in the linear fibers of carbon fiber composites - Use winding geometry changes to alter penetration depth and characterize damage Detection/characterization of impact and other damage and monitoring of strain/stress as a function of depth and fiber orientation is accomplished by modeling the fiber properties/orientation/density/contact. Simplified models are being used now with advanced models still under development. Funding - NASA for micromechanical model development and application to composite overwrapped pressure vessels (COPVs) - Army for rotorblade NDT - Navy for NDT of aircraft composites Airworthiness 2012 Slide 26

27 Questions? Phone: Website: Airworthiness 2012 Slide 27