Structural Composite Materials F.C. Campbell The Materials Information Society ASM International Materials Park, Ohio 44073-0002 www.asminternational.org
Contents Preface About the Author xi xv Chapter 1 Introduction to Composite Materials 1 1.1 Isotropic, Anisotropic, and Orthotropic Materials 4 1.2 Laminates 7 1.3 Fundamental Property Relationships 8 1.4 Composites versus Metallics 10 1.5 Advantages and Disadvantages of Composite Materials 14 1.6 Applications 18 Chapter 2 Fibers and Reinforcements 31 2.1 Fiber Terminology 31 2.2 Strength of Fibers 32 2.3 Glass Fibers 33 2.4 Aramid Fibers 39 2.5 Ultra-High Molecular Weight Polyethylene Fibers 41 2.6 Carbon and Graphite Fibers 42 2.7 Woven Fabrics 49 2.8 Reinforced Mats 52 2.9 Chopped Fibers 52 2.10 Prepreg Manufacturing 52 Chapter 3 Matrix Resin Systems 63 3.1 Thermosets 64 3.2 Polyester Resins 65 3.3 Epoxy Resins 67 3.4 Bismaleimide Resins 70 3.5 Cyanate Ester Resins 71 3.6 Polyimide Resins 72 3.7 Phenolic Resins 74 3.8 Toughened Thermosets 75 3.9 Thermoplastics 81 3.9.1 Thermoplastic Composite Matrices 82 3.9.2 Thermoplastic Composite Product Forms 87 3.10 Quality Control Methods 90 3.10.1 Chemical Testing 91 3.10.2 Rheological Testing 92 3.10.3 Thermal Analysis 94 3.10.4 Glass Transition Temperature 97 3.11 Summary 99
vi / Contents Chapter 4 Fabrication Tooling 101 4.1 General Considerations 101 4.2 Thermal Management 104 4.3 Tool Fabrication 111 Chapter 5 Thermoset Composite Fabrication Processes 119 5.0 Lay-up Processes 119 5.1 WetLay-Up 119 5.2 Prepreg Lay-Up 122 5.2.1 Manual Lay-Up 123 5.2.2 Flat Ply Collation and Vacuum Forming 124 5.2.3 Roll or Tape Wrapping 125 5.2.4 Automated Methods 125 5.2.5 Vacuum Bagging 131 5.2.6 Curing 133 5.3 Low-Temperature Curing/Vacuum Bag Systems 137 5.4 Filament Winding 141 5.5 Liquid Molding 146 5.5.1 Preform Technology 148 5.5.2 Resin Injection 162 5.5.3 Priform Process 164 5.5.4 RTM Curing 166 5.5.5 RTM Tooling 167 5.5.6 RTM Defects 170 5.5.7 Vacuum-Assisted Resin Transfer Molding 172 5.6 Resin Film Infusion 174 5.7 Pultrusion 175 Chapter 6 Thermoplastic Composite Fabrication Processes 183 6.1 Thermoplastic Consolidation 183 6.2 Thermoforming 186 6.3 Thermoplastic Joining 192 Chapter 7 Processing Science of Polymer Matrix Composites 201 7.1 Kinetics 202 7.2 Viscosity 206 7.3 Heat Transfer 207 7.4 Resin Flow 209 7.4.1 Hydrostatic Resin Pressure Studies 214 7.4.2 Resin Flow Modeling 217 7.5 Voids and Porosity 219 7.5.1 Condensation-Curing Systems 226 7.6 Residual Curing Stresses 226 7.7 Cure Monitoring Techniques 232 Chapter 8 Adhesive Bonding 235 8.1 Theory of Adhesion 235 8.2 Surface Preparation 235 8.2.1 Composite Surface Preparation 237 8.2.2 Aluminum Surface Preparation 239 8.2.3 Titanium Surface Preparation 242 8.2.4 Aluminum and Titanium Primers 243 8.3 Epoxy Adhesives 244 8.3.1 Two-Part Room-Temperature Curing Epoxy Liquid and Paste Adhesives 245 8.3.2 Epoxy Film Adhesives 247
Contents / vii 8.4 Bonding Procedures 248 8.4.1 PrekittingofAdherends 249 8.4.2 Prellt Evaluation 249 8.4.3 Adhesive Application 250 8.4.4 Bondline Thickness Control 251 8.4.5 Bonding 252 Chapter 9 Sandwich and Integral Cocured Structure 255 9.1 Sandwich Structure 255 9.2 Honeycomb Core Sandwich Structure 255 9.2.1 Honeycomb Processing 264 9.2.2 Cocured Honeycomb Assemblies 267 9.3 Foam Cores 271 9.3.1 Syntactic Core 272 9.4 Integrally Cocured Unitized Structure 273 Chapter 10 Discontinuous-Fiber Composites 285 10.1 Fiber Length and Orientation 285 10.2 Discontinuous-Fiber Composite Mechanics 287 10.3 Fabrication Methods 289 10.4 Spray-Up 289 10.5 Compression Molding 290 10.5.1 Thermoset Compression Molding 290 10.5.2 Thermoplastic Compression Molding 295 10.6 Structural Reaction Injection Molding 296 10.7 Injection Molding 297 10.7.1 Thermoplastic Injection Molding 298 10.7.2 Thermoset Injection Molding 304 Chapter 11 Machining and Assembly 307 11.1 Trimming and Machining Operations 307 11.2 General Assembly Considerations 309 11.3 Hole Preparation 311 11.3.1 Manual Drilling 311 11.3.2 Power Feed Drilling 314 11.3.3 Automated Drilling 315 11.3.4 Drill Bit Geometries 316 11.3.5 Reaming 317 11.3.6 Countersinking 317 11.4 Fastener Selection and Installation 318 11.4.1 Special Considerations for Composite Joints 320 11.4.2 Solid Rivets 322 11.4.3 Pin and Collar Fasteners 323 11.4.4 Bolts and Nuts 323 11.4.5 Blind Fasteners 326 11.4.6 Interference-Fit Fasteners 328 11.5 Sealing and Painting 329 Chapter 12 Nondestructive Inspection 333 12.1 Visual Inspection 333 12.2 Ultrasonic Inspection 335 12.3 Portable Equipment 341 12.4 Radiographic Inspection 342 12.5 Thermographic Inspection 345
viii / Contents Chapter 13 Mechanical Property Test Methods 351 13.1 Specimen Preparation 351 13.2 Flexure Testing 352 13.3 Tension Testing 353 13.4 Compression Testing 354 13.5 Shear Testing 356 13.6 Open-Hole Tension and Compression 357 13.7 Bolt Bearing Strength 358 13.8 Flatwise Tension Test 361 13.9 Compression Strength After Impact 361 13.10 Fracture Toughness Testing 362 13.11 Adhesive Shear Testing 364 13.12 Adhesive Peel Testing 364 13.13 Honeycomb Flatwise Tension 367 13.14 Environmental Conditioning 367 13.15 Data Analysis 369 Chapter 14 Composite Mechanical Properties 373 14.1 Glass Fiber Composites 374 14.2 Aramid Fiber Composites 376 14.3 Carbon Fiber Composites 379 14.4 Fatigue 383 14.5 Delaminations and Impact Resistance 388 14.6 Effects of Defects 393 14.6.1 Voids and Porosity 393 14.6.2 Fiber Distortion 397 14.6.3 Fastener Hole Defects 398 Chapter 15 Environmental Degradation 401 15.1 Moisture Absorption 401 15.2 Fluids 411 15.3 Ultraviolet Radiation and Erosion 411 15.4 Lightning Strikes 412 15.5 Thermo-Oxidative Stability 415 15.6 Heat Damage 416 15.7 Flammability 417 Chapter 16 Structural Analysis 421 16.1 Lamina or Ply Fundamentals 421 16.2 Stress-Strain Relationships for a Single Ply Loaded Parallel to the Material Axes (9 = 0 or 90 ) 425 16.3 Stress-Strain Relationships for a Single Ply Loaded Off-Axis to the Material Axes (0 * 0 or 90 ) 427 16.4 Laminates and Laminate Notations 429 16.5 Laminate Analysis Classical Lamination Theory 430 16.6 Interlaminar Free-Edge Stresses 439 16.7 Failure Theories 440 16.8 Concluding Remarks 446 Chapter 17 Structural Joints Bolted and Bonded 449 17.1 Mechanically Fastened Joints 449 17.2 Mechanically Fastened Joint Analysis 450 17.3 Single-Hole Bolted Composite Joints 455 17.4 Multirow Bolted Composite Joints 459 17.5 Adhesive Bonding 463
Contents / ix 17.6 Bonded Joint Design 464 17.7 Adhesive Shear Stress-Strain 466 17.8 Bonded Joint Design Considerations 475 17.9 Stepped-Lap Adhesively Bonded Joints 479 17.10 Bonded-Bolted Joints 481 Chapter 18 Design and Certification Considerations 489 18.1 Material Selection 489 18.2 Fiber Selection 490 18.3 Product Form Selection 491 18.3.1 Discontinuous-Fiber Product Forms 492 18.3.2 Continuous-Fiber Product Forms 493 18.4 Matrix Selection 494 18.5 Fabrication Process Selection 496 18.5.1 Discontinuous-Fiber Processes 496 18.5.2 Continuous-Fiber Processes 497 18.6 Trade Studies 498 18.7 Building Block Approach 499 18.8 Design Allowables 501 18.9 Design Guidelines 503 18.10 Damage Tolerance Considerations 508 18.11 Environmental Sensitivity Considerations 512 Chapter 19 Repair 517 19.1 Fill Repairs 517 19.2 Injection Repairs 517 19.3 Bolted Repairs 520 19.4 Bonded Repairs 523 19.5 Metallic Details and Metal-Bonded Assemblies 533 Chapter 20 Metal Matrix Composites 537 20.1 Aluminum Matrix Composites 540 20.2 Discontinuous Composite Processing Methods 542 20.3 Stir Casting 542 20.4 Slurry Casting Compocasting 544 20.5 Liquid Metal Infiltration 545 20.5.1 Squeeze Casting 545 20.5.2 Pressure Infiltration Casting 545 20.5.3 Pressureless Infiltration 546 20.6 Spray Deposition 546 20.7 Powder Metallurgy Methods 548 20.8 Secondary Processing of Discontinuous MMCs 549 20.9 Continuous-Fiber Aluminum MMCs 550 20.10 Continuous-Fiber Reinforced Titanium Matrix Composites 554 20.11 Continuous-Fiber TMC Processing Methods 557 20.12 TMC Consolidation Procedures 560 20.13 Secondary Fabrication of TMCs 562 20.14 Particle-Reinforced TMCs 566 20.15 Fiber Metal Laminates 567 Chapter 21 Ceramic Matrix Composites 573 21.1 Reinforcements 575 21.2 Matrix Materials 578 21.3 Interfacial Coatings 580 21.4 Fiber Architectures 580
x / Contents 21.5 Fabrication Methods 581 21.6 Powder Processing 581 21.7 Slurry Infiltration and Consolidation 583 21.8 Polymer Infiltration and Pyrolysis (PIP) 584 21.8.1 Space Shuttle C-C Process 585 21.8.2 Conventional PIP Processes 587 21.8.3 Sol-Gel Infiltration 588 21.9 Chemical Vapor Infiltration (CVI) 589 21.10 Directed Metal Oxidation (DMO) 592 21.11 Liquid Silicon Infiltration (LSI) 594 Appendix A Metric Conversion Factors 597 Index 599