||MICRO-MOLDING FABRICATION AND AERODYNAMIC ANALYSIS OF CORRUGATED FLAPPING WING
||Department of Mechanical and Electro-Mechanical Engineering
||This thesis deals with the study of the corrugated patterns on flapping wings. The corrugated wing design is generally seen in insects. Insect wings with the corrugated topological features give themselves excellent stability and high load-bearing capacity during flapping and hovering. It is believed that the appropriate corrugated structures on insect wings enhance the aerodynamic performance.
We use the innovative fabrication process using the micro-molding methodology to fabricate the 20 cm flapping wing, which is composed of the corrugated wing inspired by the dragonfly wing. The mother mold is made firstly by a 3D printer according to natural flyers design, and secondly the demolded PDMS is served a the final molding material for corrugated wings. Parylene was selected as the wing material as it mechanical properties comparable to real insect wing. The thickness of the wing was selected as 40μm. The wing was being installed on two configurations. The first is mono wings, and the other is bi wings. Both were compared to the flat membrane wing with the same shape, size, and thickness. The lift signal was measured by the load cell in a wind tunnel. The tests show that the corrugated wing has 22% improvement in lift compared to the flat membrane wing. The dynamic characterization of the corrugated wings is done by using high-speed photography as well.
Another methodology for fabrication of wing was developed using microelectromechanical systems (MEMS) process. In this methodology, the anisotropic etching was done to form the V-grooves on a silicon wafer, and this etched silicon wafer acts as the mold for the corrugated wing. SU-8 and parylene membrane form an elegant structure, approaching the real wings not only in material conception but also in mechanical performance. Based on the insect wing, the sandwich microstructure was developed where Parylene was used as the membrane of the wing, and SU8 was used as the vein. The thickness of the wing can be varied in order to get different size, shape, and thickness of the artificial wing.
We conclude that natural wings can be well mimicked in material understanding, size, weight, mass distribution venation, and wing rigidity using the “SU8-parylene” composite materials. This methodology gives the wing 25% larger stiffness than the flat membrane wing so that pinning at the wing trailing edge of the central-line fuselage is not necessary. It can matches with the natural flyers’ wing structure and motion, e.g., performing wing rotation or avian flapping in the future.
||TABLE OF CONTENTS
CHINESE ABSTRACT II
ENGLISH ABSTRACT: III
TABLE OF CONTENTS VI
LIST OF FIGURE VIII
LIST OF TABLE XI
CHAPTER 1: INTRODUCTION AND LITERATURE REVIEW 1
1.1 INTRODUCTION 1
1.2 MICRO AERIAL VEHICLE 2
1.3 VARIOUS MAVS CAME INTO PICTURE 3
1.4 INSECT WING 7
1.5 AEROELASTIC WING DYNAMICS 8
1.6 LITERATURE REVIEW 8
1.6.1 FLEXIBLE WING DESIGN 8
1.6.2 WING FABRICATION 10
1.7 RESEARCH MOTIVATION 14
1.8 THESIS OUTLOOK 14
CHAPTER 2: DRAGONFLY WING THEORITICAL BASICS AND SIMPLIFIED CORRUGATED WING FABRIGATION 16
2.1 DRAGONFLY 16
2.2 DRAGONFLY WING STRUCTURE AND CORRUGATIONS 17
2.3 THICKNESS EFFECT FOR CORRUGATED WING 19
2.4 3D PRINTING 20
2.5 DESIGN OF SIMPLE DRAGONFLY CORRUGATED WING 21
2.6 3D PRINTING OF A DRAGONFLY WING 24
2.7 MAKING PDMS MOLD FROM 3D PRINTED MASTER MOLD 24
CHAPTER 3: CORRUGATED WING AERODYNAMIC TESTING 28
3.1 MECHANISM 28
3.2 WING SETUP IN FWMAV 29
3.3 FLEXURAL STIFFNESS EFFECT ON CORRUGATED WING 30
3.4 WING BEAT CYCLE WITH CORRUGATED WING 32
3.4.1 EVANS MECHANISM 32
3.4.2 E-BIRD MECHANISM 32
3.5 TETHERING FLIGHT TEST 34
3.5.1 EVANS MECHANISM 35
3.5.2 E- BIRD MECHANISM 36
3.6 WIND TUNNEL TESTING 36
3.6.1 LIFT COMPARISON USING EVANS MECHANISM 38
3.6.2 LIFT COMPARISON USING E-BIRD MECHANISM 41
CHAPTER 4: CORRUGATED WING USING MEMS PROCESS 43
4.1 MATERIAL STUDY 43
4.1.1 MATERIAL OF NATURAL INSECT WINGS AND THEIR PROPERTIES 43
4.1.2 MATERIAL CHOICE CRITERIA FOR ARTIFICIAL INSECT WINGS 43
4.1.3 SU-8 AND PARYLENE-C: MATERIAL CANDIDATES FOR ARTIFICIAL INSECT WINGS 44
4.2 MICRO CT SCANNING 45
4.3 STRUCTURE DESIGN FOR ARTIFICIAL WING 46
4.4 VERIFICATION OF THE GROOVE ACCORDANCE TO THE CORRUGATION 48
4.5 FABRICATION PROCESS FOR ARTIFICIAL WING 49
4.6 CHARACTERIZATION OF MEMS WING 52
4.7 WING BEAT CYCLE FOR MEMS CORRUGATED WING 54
4.8 TETHERING FLIGHT TEST FOR MEMS WING 58
CHAPTER 5: CONCLUTION AND FUTURE WORK 60
5.1 SIMPLE CORRUGATED WING USING 3D PRINTED MOLD 60
5.2 CORRUGATED WING INSPIRED BY INSECT 60
5.3 FUTURE WORK 61
APPENDIX A 74
APPENDIX B 77
APPENDIX C 79
APPENDIX D 81
APPENDIX E 88
LIST OF FIGURE
Figure 1.1 Black Widow MAV 4
Figure 1.2 Different variation of the Delfly 4
Figure 1.3 Hybrid flapping-fixed wing MAV 6
Figure 1.4 Ornithopter by Petter Muren 6
Figure 1.5 Nano Hummingbird 7
Figure 1.6 Spanwise flexural stiffness of various insect species versus wingspan. 9
Figure 2.1 Dragonfly specimen 16
Figure 2.2 Time-averaged streamlines 18
Figure 2.3 Nano level pattern of dragonfly wing 18
Figure 2.4 An almost ball-shaped water droplet on wing membrane of a dragonfly 19
Figure 2.5The two-dimensional airfoils used in the numerical simulatio 19
Figure 2.6 Velocity magnitude for the airfoil at Re 5000 in COMSOL 20
Figure 2.7 Lift generated with different airfoil at Re 5000 in COMSOL 20
Figure 2.8 Layering of the melted material from the extrusion nozzle 21
Figure 2.9 Drawing of a dragonfly forewing 22
Figure 2.10 Mother mold design draft 23
Figure 2.11 3D designed wing using 3 profile structure 23
Figure 2.12 Isometric view of 3D dragonfly wing 23
Figure 2.13 Height variation in the wing 24
Figure 2.14 3D printed mold 24
Figure 2.15 Mold fabrication using PDMS 25
Figure 2.16 Mold fabrication using PDMS 25
Figure 2.17 LH 300 parylene Coater 26
Figure 2.18 Parylene-C deposition process 26
Figure 2.19 Parylene-C Based corrugated wing 27
Figure 3.1 Mechanism used 28
Figure 3.2 Setup for (a) Evans mechanisms. (b) E-Bird mechanisms 29
Figure 3.3 Vertical deflection of corrugated wing 31
Figure 3.4 Wing beat cycle for Evans mechanism 33
Figure 3.5 Wing beat cycle for E-bird mechanism 34
Figure 3.6 Control of flapping MAV 35
Figure 3.7 Evans mechanism tethering flight testing for cursing 35
Figure 3.8 Evans mechanism tethering flight test at high inclined angle 36
Figure 3.9 E- bird mechanism tethering flight at high inclined angle 36
Figure 3.10 Wind tunnel Testing Setup 37
Figure 3.11 Load-cell (Bertec Corp.). 38
Figure 3.12 Lift coefficient vs Reynolds number for Evans machanism 39
Figure 3.13 FFT using MATLAB for flat wing with Evans mechanism 39
Figure 3.14 Waveform flapping trend for flat wing with Evans mechanism 40
Figure 3.15 FFT using MATLAB for corrugated wing with Evans mechanism 40
Figure 3.16 Waveform flapping trend for corrugated wing with Evans mechanism 40
Figure 3.17 Lift coefficient vs Reynolds number for E-Bird machanism 41
Figure 3.18 FFT using MATLAB for flat wing with E-bird mechanism 41
Figure 3.19 Waveform flapping trend for flat wing with E-bird mechanism 42
Figure 3.20 FFT using MATLAB for corrugated wing with E-bird mechanism 42
Figure 3.21 Waveform flapping trend for corrugated wing with E-bird mechanism 42
Figure 4.1Material property charts 44
Figure 4.2 Flow chart for Micro CT scan processing 46
Figure 4.3 Mask design for artificial wing 47
Figure 4.4 Compensation patter for the anisotropic etching of silicon wafer 48
Figure 4.5 Verification of Anisotropic etching using silicon wafer (100) 49
Figure 4.6 Step by step process of MEMS fabrication of wing 50
Figure 4.7 TMAH etching setup 51
Figure 4.8 TMAH etched surface for corrugated wing artificial wing 51
Figure 4.9 Artificial corrugated cicada wing 52
Figure 4.10 Artificial corrugated dragonfly wing 52
Figure 4.11 The optical and SEM pictures for the fabricated wings (a) 53
Figure 4.12 Vertical deflection of MEMS wing 54
Figure 4.13 Wing setup for testing wing beat cycle 54
Figure 4.14 Wind beat frequency for MEMS wing at 2V 55
Figure 4.15 Wind beat frequency for MEMS wing at 2.5V 56
Figure 4.16 Wind beat frequency for MEMS wing at 3V 57
Figure 4.17 MAV setup with MEMS wing 58
Figure 4.18 MEMS wing tethering flight testing at low positive inclined angle 59
Figure 4.19 MEMS wing tethering flight testing at high inclined angle 59
Figure A-1CT Scan image after 3D reconstruction processing for forewing 76
Figure A-2 CT Scan image after 3D reconstruction processing for hindwing 76
Figure C-1 Lift vs wing speed for Evans mechanism 78
Figure C-2 Lift vs wind speed for E-bird 10 -70 inclined angle 78
Figure D-1 Silicon wafer of orientation 81
Figure D-2 High temperature furnace for thermal oxidation 81
Figure D-3 Process flow positive and negative photoresist 82
Figure D-4 TMAH etching setup at 60 ℃ and 25% 85
Figure D-5 TMAH etching after 1 hour 85
Figure D-6 TMAH etching after 3 hour 86
Figure D-7 TMAH etching after 12 hour 86
Figure D-8 TMAH etching after 24 hour 87
Figure D-9 TMAH 25% etching rate at 60℃ 87
Figure E-1 Flight trajectory 88
Figure E-2 Mesh formation for both corrugated and flat wing. 89
Figure E-3 The instant velocity contours around a corrugated airfoil 90
Figure E-4 Setup for finding lift 91
Figure E-5 Setup for drag 91
Figure E-6 Generation of lift and drag from corrugated wing 91
Figure E-7 Lift and drag trend and drag tend from corrugated wing 92
Figure E-8 Generation of lift and drag from flat wing 92
Figure E-9 Lift and drag trend and drag tend from corrugated wing 92
LIST OF TABLE
Table 1.1 Various artificial wings fabricated using different wing and material 11
Table 2.1 Wing parameter 27
Table 3.1 Parameters of the mechanism used 29
Table 3.2 Component weight distribution for Evans and E-bird mechanism 30
Table 3. 3 Specification of wind tunnel 37
Table 4.1 Mechanical properties of natural insect and artificial insect candidature 45
Table 5.1 Comparison between different wing 62
Table D.1 Etching rate for TMAH 87
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