Electromagnetic Environmental Concerns

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Electromagnetic Environmental Concerns for Carbon-Fiber Composite Airframes - Mark Ewing, Sarah Seguin, Brian Cordill, Rick Hale and Ron Barrett-Gonzalez University of Kansas School of Engineering - 4th Quarter 2010 Report

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Electromagnetic Environmental Concerns for Carbon-Fiber Composite Airframes: 

1 Electromagnetic Environmental Concerns for Carbon-Fiber Composite Airframes Mark Ewing, Sarah Seguin, Brian Cordill, Rick Hale and Ron Barrett-Gonzalez University of Kansas School of Engineering 4th Quarter 2010 Report Kansas Aircraft Design and Manufacturing Research Center

ADMRC POCs: 

2 ADMRC POCs Hawker-Beechcraft Howard Jordan Cleo Neal Jeff Stock Cessna Jeff Phillips Billy Martin Spirit Chi Nwoke

Background: 

3 Background Shielding to prevent EMI in metal aircraft has been relatively straightforward Sources have historically been small in number Aluminum structure helps defeat EMI Now there are more sources of EMI Multiple sources inside the aircraft Very high intensity sources from military/terrorists Carbon-fiber structure poses EMI challenges Certification for EMC: the bar is being raised More convincing analysis and test requirements Higher frequencies Higher field strengths

Project Objectives: 

4 Project Objectives Understand performance of carbon-fiber structures in High Intensity Radio Frequency (HIRF) environments Provide Kansas industry with new employees with electromagnetic effects (EME) familiarity Electromagnetic interference (EMI) Electromagnetic compatibility (EMC) Identify directions for further collaboration

Benefits to ADMRC Members: 

5 Benefits to ADMRC Members Become pro-active regarding certification By understanding performance of carbon-fiber structures in HIRF environments Help build a workforce able to deal with the emerging focus on EME By providing Kansas industry with new employees with EME familiarity, both test and analysis Have EME experts on your team By identifying directions for further collaboration

(Original) Deliverables: 

6 (Original) Deliverables Year 1 Develop a prototype testbed for HIRF-testing Report on preliminary test results Report on EME analysis Year 2 Report on tests in new anechoic chamber Report on test/analysis correlation Report on simulated lightning tests (if done) Recommendations for further test and analysis

Team Meeting – 14 June: 

7 Team Meeting – 14 June Discussed grant proposal Recommended focus on HIRF Concurred with 'building block' approach Simple cylinder to start Work up to aircraft Some interest in manufacturing issues

Year 1 Proposed Activities(all essentially accomplished): 

8 Year 1 Proposed Activities (all essentially accomplished) Identify carbon-fiber structures and environments for analysis and test Develop analytical modeling capability Stand up a prototype test facility

Task 1: Identify carbon-fiber structures and environments for analysis and test: 

9 Task 1: Identify carbon-fiber structures and environments for analysis and test Test articles selected for year 1 studies Aluminum tube (12’ long, 32' diameter, 3/16' thick) Meridian UAV Fuselage OML tooling (very simple shape) Wing alone (somewhat more complex) Full UAV Test conditions Test article on tarmac External excitation Measurements inside

Meridian UAV: 

10 Meridian UAV Up to 8 antennas will transmit at 900 MHz through 3 km of antarctic and arctic ice

Meridian OML toolall carbon-fiber—no substructure: 

11 Meridian OML tool all carbon-fiber—no substructure

Meridian Wingrelatively simple structure: 

12 Meridian Wing relatively simple structure

Meridian OML toolall carbon-fiber—no substructure: 

13 Task 2: Develop analytical modeling capability Reviewed NIST TN 1548 in detail 'Electromagnetic Airframe Penetration Measurements of a Beechcraft Premier 1A' Devised analytical approach to parallel NIST approach Establish analysis capability with Ansoft HFSS Canonical Problem Model built for 'sanity check' on a very simple problem Aluminum tube To validate test/analysis—basis for IEEE conference paper Meridian UAV To be analyzed after dielectric properties are measured To be tested using the same process as the tube

Meridian UAV: 

14 Method Validation By solving a conical problem first, different simulation methods can be evaluated and tested. Conical problem of choice: Uniform Plane Wave Incident Normal to a Surface

Task 1: Identify carbon-fiber structures and environments for analysis and test: 

15 Shielding Effectiveness – Canonical Problem HFSS Simulation Results Exact Solution from theory Sheilding Effectiveness (SE) vs frequency matches 'close enough', but…

Meridian UAV: 

16 Evaluation of Different Methods of processing EM field solution to get SE SE via 'Port' Method SE via Poynting Vector Integration Method After alternative processing techniques, the predictions match very well

Meridian OML toolall carbon-fiber—no substructure: 

17 Validated analysis concept Create a model of the physical structure 'Rove' a signal source to multiple azimuthal positions Output the coupling coefficients along mutually-orthgonal planes within the test article Compute the penetration/shielding effectiveness from the coupling coefficients Compare with test results for validation

Meridian Wingrelatively simple structure: 

18 Aluminum Airframe 'Analog' An open-ended aluminum cylinder was selected to act as an airframe analog. Readily available 1st order approximation of a wing-and-cylinder class of aircraft

Task 2: Develop analytical modeling capability: 

19 Analog Airframe Simulations The analog acts similar to a circular waveguide projecting most of the energy out either end of the cylinder. Radiation pattern (right), shows large lobes projected from either end with side lobes from constructive and destructive interference.

Method Validation: 

20 Simulation Validation Apply Antenna Theory 2-Element Array Factor Approximately Element Pattern Peaks of the array factor closely line up to the total dir. With the weighting approximately in line with the element pattern.

Shielding Effectiveness – Canonical Problem: 

21 Current Simulation Work Working on modeling ETS open boundary quad-ridged horn Necessary because the antenna type dramatically affects measurements Dramatically increase the simulations bandwidth. Extend simulation to include measurement antenna

Evaluation of Different Methods of processing EM field solution to get SE: 

22 Task 3: Stand up a prototype test facility Equipment purchased Two ETS Lindgren 3164-06 horn antennas (frequency range 300 MHz to 6 GHz) Equipment borrowed Agilent N5230C network analyzer (300 kHz – 20 GHz) Test facility used for 1st Al cylinder tests Results used for technical paper for conference

Validated analysis concept: 

23 Measurement Method After a search of literature, a measurement method developed at NIST for the measurement of shielding effectiveness (SE) of aircraft was adopted. Method consists of two path loss measurements With unobstructed line of sight With one antenna place inside the aircraft. Measurements are repeated in an arc around the aircraft to measure changes in SE with respect to angle.

Aluminum Airframe 'Analog': 

24 Post-Processing Measurements are post-processed to find the shielding effectiveness. Time-gating process used to remove ground bounce and multipath. Ratio of resulting 'clean' measurements is indicative of the shielding effectiveness. SE

Analog Airframe Simulations: 

25 Analog Airframe Measurements Coarse measurements taken a KU Aerospace facility. Preliminary results show agreement between expected SE and measured SE. Further results will be presented at a technical conference

Simulation Validation: 

26 Analog Airframe Measurement Process Refinement There are several diffident areas in preliminary work that warrant refinement. Simulation Limited to single frequencies  Extend to wider bandwidth Simulated with simple dipole radiator  Extend simulation to include actual measurement antenna. Measurement Coarse angular measurements  Refine angle measurement method to reduce angular uncertainty.

Analog Airframe Simulations: 

27 Programmatic Issues Students Unable to attract qualified students in Spring 'High-end' graduate student arrived in August Has MS + background in satellite EMC w/ no-cost extension, will hire 2nd student in Spring Expenses Have underspent this year—need a no-cost extension Re-programmed $15K to equipment ($25K total) Have enough $s left (~$30K) to Pay grad student #1 all of 2011 Pay grad student #2 in the Fall (have $s for Spring and summer) No further faculty salary to be paid

Simulation Validation: 

28 New Year 2 Plan (with no-cost extension) Analysis Continue to refine analysis of Aluminum tube Antenna modeling underway Continue analysis of Meridian UAV Analytical model already constructed Measure and use dielectric properties of composite Test Repeat SE tests on Aluminum cylinder Refine test process Use new antennas just purchased Perform SE experiments on Meridian UAV Validation Final report on findings on carbon-fiber structures

Current Simulation Work: 

29 Conclusion We’re off to a good start Great, experienced graduate student on board Preliminary analysis/test correlation for aluminum cylinder is very promising With a no-cost extension We’ll do more than we promised for the 1st year Refine the analysis and test processes using the cylinder Perform analysis and test on the carbon-fiber fuselage Begin to study 'box within a tube' penetration phenomena Our team will be able to answer fundamental questions on analyzing HIRF effects on composite structures

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