Contents
INTRODUCTION 1
Part 1 Structure Design Basis for Wind Turbine Blade
Chapter 1 BASIC PRINCIPLES 9
1.1 DESIGN COORDINATION 9
1.2 DESIGN BASIS 12
1.3 STRUCTURE DESIGN 13
1.4 STRUCTURE WEIGHT AND COST CONTROL 15
Chapter 2 COMPOSITE BASIS 17
2.1 BLADE COMPOSITE STRUCTURE COMPONENTS 21
2.2 BLADE STRUCTURAL MATERIAL 25
2.3 REINFORCED FIBRE 25
2.4 RESIN 27
2.5 OTHER STRUCTURAL MATERIALS 28
2.6 MATERIAL SELECTION 30
2.7 MECHANICAL TEST OF COMPOSITES 30
2.7.1 Testing Techniques of Composites 30
2.7.2 Test Process of Composites 34
2.8 MANUFACTURABILITY OF COMPOSITES FOR BLADE 36
Chapter 3 STRUCTURE DESIGN BASIS 43
3.1 DESIGN BASIS 43
3.1.1 Airfoil Contour 43
3.1.2 Load Characteristics 45
3.1.3 Load-carrying Forms 57
3.2 CONFIGURATION DESIGN 59
3.3 STRUCTURE DESIGN PROCESS 61
Part 2 Structure Design for Wind Turbine Blade
Chapter 4 STRUCTURAL COMPONENT DESIGN 67
4.1 SPAR CAP DESIGN 67
4.1.1 Configuration Categories for Spar Cap 70
4.1.2 Spar Cap of Glass-fibre Fabric 72
4.1.3 Spar Cap of Carbon-fibre Fabric 74
4.1.4 Spar Cap of Laminated Bamboo-wood 76
4.1.5 Spar Caps Made of Mixed Material 78
4.1.6 Structure Design for Spar Caps 78
4.1.7 Spar Cap Manufacturing Process Description 79
4.2 DESIGN OF WEB AND FLANGE ADHESIVE BONDING 83
4.2.1 Web Configuration Types 84
4.2.2 Web Arrangements 88
4.2.3 Web Structure Design 89
4.2.4 Prospect of Web Processing 96
4.3 SKIN DESIGN 96
4.3.1 Configuration Design for Skin 97
4.3.2 Summary of Skin Process 98
4.4 SANDWICH STRUCTURE DESIGN 99
4.4.1 Sandwich Structure Configurations 101
4.4.2 Sandwich Structure Design 101
4.4.3 Summary of Sandwich Structure Processes 104
4.5 LEADING EDGE UD DESIGN AND LEADING EDGE ADHESIVE BONDING 105
4.5.1 Structure Design for Leading edge UD 106
4.5.2 Adhesive Bonding Forms 108
4.6 TRAILING EDGE UD DESIGN AND TRAILING EDGE ADHESIVE BONDING 108
4.6.1 Design for Trailing Edge UD Configuration 109
4.6.2 Structure Design for Trailing Edge 111
4.6.3 Summary of Trailing Edge Processing 119
4.7 ROOT REINFORCEMENT DESIGN 121
4.7.1 Structure Design for Root Reinforcement 121
4.7.2 Process Overview of Blade Root Reinforcing Layer 122
4.8 CONNECTION DESIGN OF BLADE ROOT 123
4.8.1 Different Method for Mounting Bolt 124
4.8.2 Configuration Design of Embedded Bolts 126
4.8.3 Structure Design for Embedded Bolts 130
4.8.4 Structure Design for T-bolt 137
4.8.5 Overview of Blade Root Process Test 138
4.9 DISCUSSION ABOUT OPTIMIZATION DESIGN 138
4.9.1 Influence of Optimization and Non-optimization 138
4.9.2 Structure Index 138
Chapter 5 DESIGN OF FUNCTIONAL PARTS 140
5.1 BLADE TIP DESIGN 140
5.2 LIGHTNING PROTECTION DESIGN 140
5.2.1 Air-termination System 142
5.2.2 Lightning Protection Tests on Blades 143
5.3 GEL COATS AND PAINTS 144
5.4 DESIGN OF REINFORCED LAYERS FOR
TRANSPORTATION 145
5.5 BLADE ROOT COVER DESIGN 145
5.6 DESIGN OF BALANCING CHAMBERS 146
5.7 RAIN DEFLECTOR DESIGN 146
5.8 PE PIPES CONNECTED WITH DOUBLE WEBS 147
5.9 OTHER DESIGNS 147
Part 3 Structure Design Methods for Wind Turbine Blade
Chapter 6 STRUCTURE VERIFICATION PRINCIPLES 151
6.1 GENERAL PRINCIPLES OF STRUCTURE VERIFICATION 152
6.2 BLADE STRUCTURE VERIFICATION METHODS 152
6.3 GENERAL INTRODUCTION OF BLADE STRUCTURE VERIFICATION 154
6.3.1 Blade Topological Graph 154
6.3.2 Stress Characteristics of Blade Components 154
6.4 STRENGTH ANALYSIS 157
6.5 STABILITY ANALYSIS 157
6.6 DEFORMATION ANALYSIS 161
6.7 DYNAMIC CHARACTERISTIC ANALYSIS 162
6.8 ADHESIVE BONDING ANALYSIS 162
6.9 INTERLAMINAR ANALYSIS 162
6.10 FATIGUE ANALYSIS 163
6.11 ADVANCED ANALYSIS 164
Chapter 7 UNIDIMENSIONAL METHOD 165
7.1 I-BEAM THEORY 165
7.2 SIMPLIFICATION OF BLADE CROSS SECTION MODEL 168
7.3 CALCULATION OF BLADE CROSS SECTION STRENGTH 171
7.4 STRENGTH ANALYSIS OF BLADE CROSS SECTION 174
7.5 CALCULATION OF BLADE BENDING DEFORMATION 175
7.6 DEFLECTION ANALYSIS OF BLADE SECTION 177
7.7 DEVIATION ANALYSIS WITH UNIDIMENSIONAL METHOD 177
7.8 APPLICATION DEVELOPMENT OF UNIDIMENSIONAL METHOD 181
Chapter 8 2D METHOD 183
8.1 BLADE STRENGTH CALCULATION 184
8.1.1 Normal Stress Calculation of Thin-walled Airfoil Structure 184
8.1.2 Shear Stress Calculation of Thin-walled Airfoil 190
8.1.3 Calculation of Blade Deflection 197
8.2 CALCULATION OF BLADE NATURAL FREQUENCY AND CHARACTERISTIC MODE 201
8.3 EQUIVALENT FATIGUE LOAD METHOD FOR FATIGUE DAMAGE CALCULATION 203
8.4 2D ENGINEERING ALGORITHM 204
8.5 FINITE ELEMENT METHOD OF 2D UNIFORM CROSS SECTION 206
8.5.1 Finite element analysis of 2D shell model 206
8.5.2 Finite element verification of 2D solid model 209
Chapter 9 3D METHOD 211
9.1 FINITE ELEMENT ANALYSIS OF WIND TURBINE BLADES 212
9.2 FINITE ELEMENT MODELING OF BLADES 212
9.2.1 Geometrical Shape 213
9.2.2 The Coordinate System 214
9.2.3 Structural Configuration 216
9.2.4 Meshing 216
9.2.5 Element Normal and Element Coordinate System 218
9.2.6 Material Properties 219
9.2.7 Direction of Material 220
9.2.8 Spanwise Divisions 220
9.2.9 Element Properties 220
9.2.10 Mass of a Blade 222
9.3 LOCAL REFINEMENT OF BLADE FINITE ELEMENT MODEL 223
9.3.1 Refinement of TE Model 223
9.3.2 Adhesive Bonding of Web Flange and Shell 224
9.3.3 Blade Root Model 224
9.3.4 Adjacent Component of Root Model 225
9.3.5 Point Mass of Blade 225
9.4 FINITE ELEMENT BOUNDARY AND LOADING OF BLADE 226
9.4.1 Finite Element Boundary Conditions 226
9.4.2 Ultimate Loading Form in Blade FEA 226
9.4.3 Ultimate Envelop Load 227
9.4.4 Concentrated Force Ultimate Loading 230
9.4.5 Distributed Ultimate Loading 231
9.4.6 Loading Type of Test Load 240
9.4.7 Gravitational Load 243
9.4.8 Fatigue Load 243
Chapter 10 OTHER METHODS 244
10.1 PROCEDURE OF BLADE MOULDING 244
10.2 BLADE DATABASE 244
Part 4 Structure Component Design Methods for Wind Turbine Blade
Chapter 11 BASIC VERIFICATION ANALYSIS 249
11.1 BASIC VERIFICATION OF BLADE 249
11.2 SAFETY FACTOR OF STRUCTURE VERIFICATION 250
11.2.1 Safety Factor of Structure Verification Defined in GL 2010 250
11.2.2 Safety Factor of DNV Structure Verification 252
11.3 STRENGTH VERIFICATION 254
11.3.1 Failure Criterion 254
11.3.2 Overall Ultimate Strength Verification 255
11.3.3 Strength Verification of Hoisting Condition 256
11.4 STIFFNESS VERIFICATION 259
11.4.1 Criterion of Deflection Analysis 259
11.4.2 Stiffness Distribution 260
11.4.3 Tip Deflection 261
11.5 ANALYSIS OF VIBRATION CHARACTERISTICS 262
11.5.1 Natural Frequency and Mode of Vibration 262
11.5.2 Campbell Chart of Blade Vibration 266
11.6 OVERALL BUCKLING OF BLADE 270
Chapter 12 LAMINATE ANALYSIS 272
12.1 THEORY OF LAMINATE 272
12.1.1 The Theory of Shell Theory to Composite Material 273
12.1.2 Feature of Laminate 275
12.1.3 Performance and Stiffness of Laminate 276
12.1.4 The Strength Analysis of Laminate 279
12.1.5 The Design Value for Structure 280
12.2 DESIGN OF LAMINATE 281
12.2.1 The Stiffness Prediction and Design of Laminate 281
12.2.2 Preliminary Design of Laminate 282
12.2.3 Consideration of Environmental Influence 282
12.3 BUCKLING OF THE LAMINATE 283
12.3.1 Buckling Calculation Method 284
12.3.2 Boundary Conditions 286
12.3.3 Examples of Theoretical Solution 286
12.3.4 Engineering Algorithm 290
12.3.5 FEM Example 292
12.3.6 FEA of Laminate 293
12.4 FIBRE FAILURE ANALYSIS 294
12.5 RESIN FAILURE ANALYSIS 296
12.6 APPLICATION OF LAMINATES ON BLADES 300
Chapter 13 ANALYSIS OF SANDWICH STRUCTURE 302
13.1 BASIS OF SANDWICH STRUCTURE 302
13.2 SANDWICH STRUCTURE DEAIGN 303
13.2.1 Design Principle of Sandwich Structure 303
13.2.2 Design Key Points 304
13.3 ANALYSIS OF SANDWICH STRUCTURE 304
13.3.1 Basic Parameters 304
13.3.2 Analysis of Local Failure 305
13.4 ANALYSIS METHODS OF SANDWICH STRUCTURE 307
13.4.1 Sandwich with Isotropic Panels 307
13.4.2 Sandwich with Orthotropic Panels 315
13.4.3 Engineering Algorithm of Local Instability 316
13.4.4 Finite Element Analysis 318
13.4.5 Local Secondary Analysis Method 319
13.5 APPLICATION OF SANDWICH STRUCTURE ON BLADES .320
13.6 ANALYSIS OF WEB BUCKLING 320
13.7 ANALYSIS OF BLADE LOCAL BUCKLING 325
13.8 BUCKLING ANALYSIS OF BLADE CROSS SECTION 327
Chapter 14 ANALYSIS OF ADHESIVE BONDING 328
14.1 ADHESIVE BONDING 328
14.1.1 Adhesive Characteristics 329
14.1.2 Advantages and Disadvantages of Composite Bonding 330
14.2 DESIGN OF ADHESIVE BONDING 332
14.2.1 General Design Principles 332
14.2.2 Basic Failure Modes 332
14.2.3 Basic Bonding Methods 333
14.2.4 Selection of Geometric Parameters 334
14.2.5 Fibre Direction 336
14.2.6 Design of Bonding Detail 337
14.3 BONDING ENGINEERING ALGORITHM 338
14.3.1 Calculation of Static Strength 338
14.3.2 Durability Analysis 342
14.4 ANALYSIS OF ADHESIVE BONDING 343
14.5 ADHESIVE BONDING APPLICATION ON BLADE 345
14.5.1 Bonding between Web Flanges and Shells 346
14.5.2 Bonding of Trailing Edge 347
14.5.3 Control of Bonding Processing 348
Chapter 15 ANALYSIS OF BOLTED CONNECTION 349
15.1 STRUCTURE VERIFICATION OF BLADE ROOT WITH MBEDDED INSERTS 350
15.1.1 Types of the Root End 350
15.1.2 Global Finite Element Analysis 354
15.1.3 Local Analysis of Contact Surface 359
15.2 STRUCTURE VERIFICATION OF T-BOLT PROCESSING 369
15.2.1 Structure Analysis Procedure 369
15.2.2 Global Finite Element Analysis 370
15.2.3 Bolt Engineering Method 372
Part 5 Special Subject for Structure Design of Wind Turbine Blade
Chapter 16 FATIGUE ANALYSIS 377
16.1 THEORETICAL BASIS 377
16.1.1 Cyclic Load 378
16.1.2 Fatigue Lifetime 379
16.1.3 Stress ratio 379
16.1.4 S-N curve 381
16.1.5 Diagram of Fatigue Limit 381
16.2 FATIGUE OF COMPOSITES 383
16.2.1 Model of fatigue accumulated damage 384
16.2.2 Estimation Method of Fatigue Lifetime 386
16.3 VERIFICATION PROCESS OF BLADE FATIGUE 387
16.4 FATIGUE LOAD 389
16.5 SELECTION OF CRITICAL POINT OF FATIGUE 389
16.6 METHODS OF BLADE FATIGUE VERIFICATION 391
16.6.1 Coordinate System 392
16.6.2 Transformation Matrix of Stress 392
16.6.3 Equivalent Stress 393
16.6.4 Rain-flow Counting 394
16.6.5 Safety Factor of Fatigue Analysis 396
16.7 IDENTIFICATION OF BLADE FATIGUE DAMAGE 397
Chapter 17 ANALYSIS OF IMPACT RESISTANCE OF BLADE 399
17.1 ANALYSIS TECHNIQUES OF IMPACT DAMAGE 400
17.1.1 Methods of Engineering Analysis 401
17.1.2 Techniques of Load Processing 402
17.2 METHODS OF EXPLICIT TIME INTEGRATION 404
17.3 CONSTITUTIVE RELATION OF MATERIAL 405
17.3.1 Material of Bird-model Impact 405
17.3.2 Material of Hail Impact 405
17.4 VERIFICATION OF RESISTANCE FOR IMPACT OF BLADE 406
17.4.1 Impact-resistance Model of Blade 407
17.4.2 Analysis of Blade Resistance for Impact 407
17.5 TEST OF BLADE RESISTANCE FOR IMPACT 408
Chapter 18 ANALYSES OF FRACTURE MECHANICS AND INTER LAMINAR 409
18.1 FRACTURE ANALYSIS of COMPOSITE MATERIALS 409
18.2 MAIN PARAMETERS IN FRACTURE MECHANICS 410
18.3 FRACTURE MECHANICS CALCULATION METHOD 411
18.3.1 Theoretical Solution of a Center Cracked Finite Width Plate 411
18.3.2 The Stress Intensity Factor and Extrapolation 412
18.3.3 Domain Method J-integration and Equivalent Integration 417
18.3.4 Strain energy release rate and virtual crack method 419
18.4 DUMMY NODE FRACTURE ELEMENT 420
18.4.1 Dummy Node Fracture Element of Linear Crack 420
18.4.2 Dummy Node Fracture Element of a Plane Crack 424
18.5 INTERLAMINAR STRESS OF COMPOSITES 427
18.5.1 Shear Stress Distribution of Interlaminar Interface 430
18.5.2 Interlaminar Shear Stress Distribution Along Thickness Direction 431
18.5.3 Interlaminar Normal Stress 431
18.5.4 Distribution of Axial Displacement on the Surface of Laminates 432
18.6 INTERLAMINAR FAILURE AND FRACTURE FAILURE OF BLADE 433
Chapter 19 RELIABILITY ANALYSIS 434
19.1 COMPOSITES DAMAGE TOLERANCE 434
19.1.1 Overview 434
19.1.2 Three Elements of Damage Tolerance 435
19.2 RELIABILITY 437
19.2.1 Technical Basis of Reliability 438
19.2.2 Reliability Evaluation Index 439
19.2.3 Reliability Design of Structural System 440
Chapter 20 FULL-SCALE TESTING OF BLADES 442
20.1 OVERVIEW 442
20.2 MATERIAL TESTING AND COMPONENT TESTING 442
20.3 INTRODUCTION OF FULL-SCALE TESTING OF BLADES 445
20.3.1 Basic Principle and Relevant Standards 445
20.3.2 Test Items and Procedures 445
20.4 BLADE DATA AND REQUIREMENTS FOR SPECIMENS 446
20.4.1 Blade Data 446
20.4.2 Requirements for Specimens 447
20.5 TEST STAND 447
20.5.1 Loading Directions 447
20.5.2 Loading Types 448
20.5.3 Other Devices and Tooling 449
20.6 DESIGN LOAD AND TEST LOAD 452
20.7 FAILURE MODES 452
20.8 MASS AND DYNAMIC PROPERTY TESTS 453
20.9 STATIC STRENGTH TEST 454
20.10 FATIGUE TEST 457
20.11 DESTRUCTIVE TEST 458
Chapter 21 SUMMARY AND PROSPECT 459
21.1 DESIGN AND PROCEDURES 459
21.2 VERIFICATION AND EXPERIENCE 461
21.3 HORIZONS BEYOND DESIGN AND VERIFICATION 462
21.4 PROSPECTS FOR THE FUTURE 463
21.5 BACK TO THE ORIGIN-STRUCTURAL MECHANICS OF COMPOSITE THIN-WALLED BARS 468
REFERENCES 470
Appendix A COORDINATE SYSTEM 472
Appendix B BLADE WB45.3 475
INDEX 477