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Jessica Landes

Characterization of the Static and Dynamic Structural Response of a Diffraction-limited Fiber Reinforced Plastic Telescope. Jessica Landes. Outline. Composite Optics 0.33 Meter (1/3 rd Scale) Prototype Mirror 1 Meter Mirror Analysis

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Jessica Landes

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  1. Characterization of the Static and Dynamic Structural Response of a Diffraction-limited Fiber Reinforced Plastic Telescope Jessica Landes

  2. Outline • Composite Optics • 0.33 Meter (1/3rd Scale) Prototype Mirror • 1 Meter Mirror Analysis • Optical Tube Assembly (OTA) for a 0.4 Meter Primary Mirror • Conclusions and Recommendations

  3. Why Composite Telescopes • Traditional glass mirror limitations • Costs • Weight • Durability • Manufacturing time • Repeatability / variability • Composites fix these problems

  4. Constraints • Global deflection constraint • Less than 1.57 E-7 meters (1/4th wavelength) • Global Modal constraint • First mode shape should be over 60 Hz • Weight • Less than traditional telescopes • Optics • Diffraction limited

  5. Outline • Composite Optics • 0.33 Meter (1/3rd Scale) Prototype Mirror • 1 Meter Mirror Analysis • Optical Tube Assembly (OTA) for a 0.4 Meter Primary Mirror • Conclusions and Recommendations

  6. 0.33 Meter Primary Mirror • Geometry • 0.33 meter diameter • 0.05 meter central hole • Front skin • 3 mm thick • Back skin • 1.5 mm thick • 25 mm tall tube core

  7. 0.33 Meter Primary Mirror • Element densities: • 27 elements around the tube • 33 along the height • Approximate Size: • 1 mm by 1 mm • 2D linear shell elements • 1,845,240 DOF

  8. Carbon / Cyanate Ester Cyanate Ester only E11 7.98E+10 Pa 3.0E+09 Pa E22 8.89E+09 Pa 3.0E+09 Pa n12 0.3142 ~ 0.3 ~ G12 5.45E+09 Pa - Pa r 1633. kg/m^3 1000 kg/m^3 a11 4.55E-07 m/m/oF 1.64E-05 m/m/oF a22 1.64E-05 m/m/oF 1.64E-05 m/m/oF Unchanged Added surface layer, 1.5 mm 0.33 Meter Mirror Material Properties

  9. Property Property Skins Skins Tube Tube Thickness of layers Thickness of layers 6.35E-5 meters 6.35E-5 meters 3.175E-5 meters 3.175E-5 meters # of layers # of layers 24 24 24 24 Family (0/45/90) Family (60/0) 25/50/25 66/33 25/50/25 66/33 Original Stacking sequence Final Stacking sequence [-60,0,60,60,0,-60,60,0, -60,-60,0,60]s [[45,-45,0,90]3]s [-60,0,60,60,0,-60,60,0, -60,-60,0,60]s [[45,-45,0,90]3]s 0.33 Meter Mirror Material Properties

  10. Laser Vibrometer Mirror Shaker LaserController SignalConditioner Computer SignalGenerator Amplifier 0.33 Meter Mirror Testing Force Transducer • Shaker excitation • Laser vibrometer measuring displacement and velocities • VibraScan software analyzing response

  11. 0.33 Meter Mirror Testing • Test area at the KU Hanger Mirror Laser Vibrometer Shaker

  12. 0.33 Meter Mirror Results

  13. 0.33 Meter Results 2-Diameteral Mode Shape Experimental Frequency = 880.6 Hz Analytical Frequency = 813.49 Hz This is similar to a Pri-Astigmatism in Optical Distortion.

  14. Outline • Composite Optics • 0.33 Meter (1/3rd Scale) Prototype Mirror • 1 Meter Mirror Analysis • Optical Tube Assembly (OTA) for a 0.4 Meter Primary Mirror • Conclusions and Recommendations

  15. 1 Meter Mirror • Geometry • 1 Meter Diameter • 0.3 Meter Central Hole • 5 cm thickness • 6.6 Meter Focal Length

  16. 1 Meter Mirror Substructure Studies • Sparse core structure • 12 radial stiffeners • 11 circumferential stiffeners • Weight = 292 grams • Dense core structure • 36 radial stiffeners • 21 circumferential stiffeners • Weight = 527 grams

  17. 900 00 900 00 1 Meter Mirror Mesh Element densities: • Circumferential stiffeners: • 10 by 360 • Radial stiffeners: • 10 by 360 • Skins: • 360 by 360 • 2D linear shell elements • 2,628,700 DOF

  18. # of Stiffeners Mass Max Deflection (m) Radial Circumferential Grams Temperature Inertial Pressure 12 11 292 1.05E-05 4.04E-07 3.67E-04 18 6 195 9.49E-06 3.07E-07 5.95E-04 18 11 299 8.91E-06 6.40E-07 4.03E-04 24 11 306 9.00E-06 3.70E-07 3.22E-04 24 21 514 8.00E-06 4.07E-07 2.08E-04 36 11 320 8.00E-06 4.07E-07 2.93E-04 36 21 527 8.56E-06 3.98E-07 1.99E-04 1 Meter Mirror Substructure Results

  19. 1 Meter Mirror Substructure Results

  20. 1 Meter Mirror Results Boundary Condition 1 Pressure load 1.99E-4 m Thermal load 8.68E-6 m

  21. 1 Meter Boundary Condition Study Boundary Condition 2 • Uniform Pressure Load: -3447 Pa Boundary Condition 3 Boundary Condition 1

  22. 1 Meter Modal Response • First Mode • 136 Hz • Tilt • Fourth Mode • 285 Hz • 2-diameteral mode

  23. Outline • Composite Optics • 0.33 Meter (1/3rd Scale) Prototype Mirror • 1 Meter Mirror Analysis • Optical Tube Assembly (OTA) for a 0.4 Meter Primary Mirror • Conclusions and Recommendations

  24. 525 mm 60 mm 220 mm Spider veins 90 mm Width = 59 mm 10 mm tabs 80 mm 0.4 Meter OTA Geometry 16.2 mm 1.68 mm

  25. Rohacell foam core ring 10 mm tabs Secondary tube Secondary veins Secondary skins Secondary tube Secondary veins Effective beam 0.4 Meter OTA Mesh • Element densities: • 10 mm tabs: • 20 by 10 • Secondary tube: • 34 by 180 • Secondary skins: • 392 by 30 • Spider veins: • 34 by 25 • Foam core ring: • 392 by 16 • Effective beam: • 34 elements 1.2 Million DOF

  26. Property Property Secondary Skins Secondary Skins Secondary Tube Secondary Tube Secondary Veins Secondary Veins Struts Struts 10 mm tabs 10 mm tabs Thickness of layers (mm) Thickness of layers (mm) 6.35E-2 6.35E-2 6.35E-2 6.35E-2 6.35E-2 6.35E-2 6.35E-2 6.35E-2 6.35E-2 1.25E-1 Material Material m46J-ex1515 m46J-ex1515 m46J-ex1515 m46J-ex1515 m46J-ex1515 m46J-ex1515 m46J-ex1515 m46J-ex1515 fortafil fortafil # of layers # of layers 24 24 24 24 24 24 12 12 80 80 Stacking sequence Stacking sequence [-60,0,60,60,0,-60,60,0,-60,-60,0,60]s [-60,0,60,60,0,-60,60,0,-60,-60,0,60]s [-60,0,60,60,0, -60]s [-60,0,60,60,0, -60]s [[45,-45,90,0,0,90, -45,45]5]s [[45,-45,90,0,0,90, -45,45]5]s 0.4 Meter OTA Materials original final

  27. Mounting brackets Shaker Mounting brackets Shaker Mounting brackets Shaker 0.4 Meter Test Set-up • 3 set up configurations

  28. 0.4 Meter OTA Results 60 HZ Cutoff

  29. Modes Below 60 Hz

  30. Outline • Composite Optics • 0.33 Meter (1/3rd Scale) Prototype Mirror • 1 Meter Mirror Analysis • Optical Tube Assembly (OTA) for a 0.4 Meter Primary Mirror • Conclusions and Recommendations

  31. Conclusions • A 0.33-meter (1/3rd Scale) primary mirror prototype with tube core • Verified within 15% • Surface flaws skewed modal results • Building confidence in the modeling techniques • Recommendations for manufacturing changes

  32. Conclusions Cont. • A 1-meter mirror • Inertial, Thermal, and Uniform Pressure Loads • Pressure loads were driving force, .2mm deflection • Exceeded the ¼ wavelength of light • Reanalysis of the constraint • This initiated a bay sizing study • A bay size of 19 mm by 19 mm • A box core substructure • Boundary conditions study • Significant effect on response

  33. Conclusions Cont. • The 0.4-meter OTA • As-manufactured OTA structure • Noise causing devices • Recommend design changes • Many modes aligned well but not all matched • a detailed modeling of attachments • modes below the 60 Hz line • 4 below • 2 on edge

  34. Acknowledgements • Balaji for aerodynamic data and advice • Wanbo for advice with the laser vibrometer software and equipment • Dr. Hale for timely and helpful feedback • My committee for their time and help with the thesis writing process • Dr. Ewing for advice about modal testing, fixturing and comparison of results • My family for understanding when I ignored them • Funding Agencies • NASA EPSCOR , NCCS-600 • NSF, AST-0321247

  35. 0.33 Meter Results • 1-Circumferential, 1-Diameteral Mode Shape • Analytical Frequency = 1435.7 Hz • Experimental Frequency = 1436 Hz • This is similar to a Sec-Coma in Optical Distortion

  36. Noise Causing Elements • Springs • Bearings • Loose bolts • Misaligned bolts

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