Design and Fabrication of an Hyper- Hemispherical ALON TM Dome for Counter MANPADS Applications May 04, 2006 Electromagnetic Windows Symposium Objective,

Design and Fabrication of an Hyper-Hemispherical ALONTM Dome for Counter

MANPADS Applications

May 04, 2006 Electromagnetic Windows Symposium

Objective, Dome Material/Fabrication:

•Mid-wave material

•Extreme environmental durability

•Technology available to ‘form’ into a monolithic hyper-hemispherical configuration

•Accurate and repeatable High-speed optical fabrication process

•Cost effective combination of materials and processing




Material Option(s) review:

•Spinel.

•Silicon

•ALON




Foreign Object Damage, testing:• Testing on ALON, Silicon and Fused Silica. • Being performed at UDRI

• Simulate aircraft foreign object damage from take-off/landing (20 m/s to 75 m/s)

• Testing being conducted by launching 3/8” diameter granite projectiles into the window samples using a .50 caliber bore compressed-gas gun.

• Parts rigidly mounted at 450 AOI• A laser photodetector system has been employed to measure the

projectile impact velocity• All parts are being photographed before and after test




Foreign Object Damage, testing:•




Strength of Material, Improvement, ALON

• The objective of the ALON strength enhancement program were to increase the strength of ALON so that high thermal shock resistant domes could be made.

• Several years of fabrication/thermal processing development yielded a significant increase to the ultimate strength of ALON

Sample Set

AVG Strength (MPa)

Standard Dev.

(MPa)

Weibull Characteristic

Strength (MPa) Weibull Modulus

Roughness side 1

Roughness side 2

2258 583 162 644 4.42 13.6 17.8 2260 460 80 512.6 8.45 13.1 19.8 2261 546 146 603 5.4 12.7 19.7 2262 461 77 463 16.0 23.5 31.7 2262_Anneal 653 218 744 3.0 23.5 31.7 2263 388 111 420 3.7 26.1 43.5 2263_Anneal 539 149 592 3.7 26.1 43.5 2264_Anneal_1 792 190 847 4.6 16.6 21.3 2264_Anneal_10 535 85 570 8 16.6 21.3 SEPT 2004 Best 700 169 750 8.5 Not Meas. Not Meas.




Strength of Material, Improvement, ALON

August 2005 Tests - Annealed ALON AIM9X Domes

S/N Test Surface/Temp. (C) Results CC CX

1578 160 130 Passed 1580 160 130 Passed 2642 160 130.9 Passed 2643 160 Not Tested Passed 2643 180 Not Tested Passed 2643 208 Not Tested Passed

Ultra Polished/added Thermal Cycling

Successful Thermal Shock-testing of Domes + much higher ultimate strength exhibited by equi-biaxial flexure testing of plano samples validates the modified material process’




‘Forming’, ALON

Technique Advantages Disadvantages

Simple and inexpensive molds Not precise shapes/excess powder required

Relatively fast Requires spray dried powder

Inexpensive molds Very slow

Complex shapes Requires large volumes of plaster relative to part

Near net shape Requires careful environmental control

Does not require spray dried powder

Very fast Expensive molds

Complex shapes Requires high volumes of wax binders

Does not require spray dried powder

Complicated and messy debind procedures

Cold Isostatic Pressing

Slip-casting

Injection Molding




‘Green’ Machining, ALON




‘High-Speed’ Optical Fabrication, ALON




Micro-Mesh Technology, Shielding

• Best solution for high IR/Visible/UV transmission with high EMI shielding

• Mesh coatings can solve many needs:

– EMI shielding

– Heating

– Radar Cross-section control

• Mesh geometry customizable based on transmission, shielding, resistance, and diffraction requirements.




Challenges and Approaches, Shielding

• Battelle’s historical dome exposure technique, laser direct-write of straight lines, is not compatible with Hyper-hemisphere shape due to pattern distortion at the “equator”.

• Battelle recently developed unique masking concept to expose complex mesh geometries on complex curved substrates.

• We are combining our new masking technology with the concept of exposing a segmented pattern in a “flower-petal” configuration.




Custom Mesh Exposure Tooling, Shielding

• Battelle developed the process from conceptual design to functional tooling

• Designed to have minimal overlap of mesh pattern (1-2mm)

• Enables non-linear grid patterns, ex hub-spoke




Thin-film Coatings

Surmet Coatings

Surmet’s proprietary PA-CVD coating processes have been used to apply coatings, conformally, to complicated shapes

DLC Coating Applied Over Metal Gear

Thick Silicon Coating Applied Over Entire Inside Surface of Semi-Conductor Chamber

DLC Coating AppliedOver Bearing Assembly




Optical Application of Surmet’s Coatings

Surmet’s PA-CVD Coating Process Will Be Used to Apply Coatings, Uniformly, Over Metal Grids ON Exterior of Hyper-

Hemispherical Dome

Thin-Film




Documents

Design and Fabrication of an Hyper- Hemispherical ALON TM Dome for Counter MANPADS Applications May 04, 2006 Electromagnetic Windows Symposium Objective,