Composites Material Usage, Design, and Analysis Handbook, Volume 3

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Composites Material Usage, Design, and Analysis Handbook, Volume 3

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Engineering Materials

Composites Materials Handbook, Volume 3
Polymer Matrix Composites
Material Usage, Design, and Analysis

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Composites Materials Handbook, Volume 3

Introduction:

Volume 3 Composites Materials Handbook provides methodologies and lessons learned for the design, analysis, manufacture, and field support of fiber-reinforced, polymeric-matrix composite structures. It also provides guidance on material and process specifications and procedures for utilization of the material data presented in Volume 2. The information provided is consistent with the guidance provided in Volume 1 and intended to be an extensive compilation of the current "best knowledge and practices" of composite materials and structures engineers and scientists from industry, government, and academia. This volume will be continually updated as the "state-of-the-art" of composites technology advances.

TOC

Foreword. ii
Summary of Changes . xvii
CHAPTER 1 GENERAL INFORMATION 1
1.1 INTRODUCTION.. 1
1.2 PURPOSE, SCOPE, AND ORGANIZATION OF VOLUME 3. 1
1.3 SYMBOLS, ABBREVIATIONS, AND SYSTEMS OF UNITS 2
1.3.1 Symbols and abbreviations. 2
1.3.1.1 Constituent properties. 7
1.3.1.2 Laminae and laminates . 8
1.3.1.3 Subscripts . 9
1.3.1.4 Superscripts.. 10
1.3.1.5 Acronyms 10
1.3.2 System of units .. 12
1.4 DEFINITIONS.. 13
CHAPTER 2 MATERIALS AND PROCESSES - THE EFFECTS OF VARIABILITY ON COMPOSITE PROPERTIES 1
2.1 INTRODUCTION.. 1
2.2 PURPOSE 1
2.3 SCOPE.. 1
2.4 CONSTITUENT MATERIALS .1
2.4.1 Fibers . 1
2.4.1.1 Carbon and graphite fibers .. 1
2.4.1.1.1 Carbon vs. graphite 2
2.4.1.1.2 General material description. 4
2.4.1.1.3 Processing . 4
2.4.1.1.4 Typical properties 6
2.4.1.2 Aramid 6
2.4.1.3 Glass 8
2.4.1.3.1 Chemical description. 8
2.4.1.3.2 Physical forms available . 9
2.4.1.3.3 Advantages and disadvantages 12
2.4.1.3.4 Common manufacture methods and variable 14
2.4.1.4 Boron 15
2.4.1.5 Alumina 17
2.4.1.6 Silicon carbide . 19
2.4.1.7 Quartz .. 21
2.4.1.8 Ultrahigh molecular weight polyethylene. .. 26
2.4.2 Resins . 29
2.4.2.1 Overview. 29
2.4.2.2 Epoxy 30
2.4.2.3 Polyester (thermosetting) .. 30
2.4.2.4 Phenolic .. 30
2.4.2.4.1 Resoles . 31
2.4.2.4.2 Novolacs .. 31
2.4.2.5 Bismaleimide 31
2.4.2.6 Polyimides . 32
2.4.2.7 Thermoplastic materials . 32
2.4.2.7.1 Semi-crystalline. 32
2.4.2.7.2 Amorphous.. 34
2.4.2.8 Specialty and emerging resin systems 36
2.4.2.8.1 Silicone.. 36
2.5 PROCESSING OF PRODUCT FORMS . 36
2.5.1 Fabrics and preforms.. 36
2.5.1.1 Woven fabrics .. 36
2.5.1.1.1 Conventional woven fabrics 36
2.5.1.1.2 Stitched or knitted fabrics. 38
2.5.1.1.3 Specialty fabrics 38
2.5.2 Preimpregnated forms 38
2.5.2.1 Prepreg roving . 38
2.5.2.2 Prepreg tape . 38
2.5.2.2.1 Conventional unidirectional tapes 38
2.5.2.2.2 Two-step unidirectional tapes 39
2.5.2.2.3 Supported unidirectional tapes . 39
2.5.2.2.4 Coated unidirectional tapes 39
2.5.2.2.5 Preplied unidirectional tapes.. 39
2.5.2.3 Prepreg fabric .. 39
2.5.2.4 Preconsolidated thermoplastic sheet 39
2.6 SHIPPING AND STORAGE PROCESSES .. 40
2.6.1 Packaging . 40
2.6.2 Shipping 40
2.6.3 Unpackaging and storage. 40
2.7 CONSTRUCTION PROCESSES 40
2.7.1 Hand lay-up.. 40
2.7.2 Automated tape placement/automated tape lamination 41
2.7.2.1 Background 41
2.7.2.2 Benefits/capabilities .. 41
2.7.2.3 Sources of variability. 41
2.7.3 Automated tow placement/fiber placement . 42
2.7.3.1 Background 42
2.7.3.2 Fiber placement process flow.. 43
2.7.3.3 Benefits/capabilities .. 43
2.7.3.4 Material product forms. 44
2.7.3.5 Special considerations . 45
2.7.4 Braiding. 47
2.7.5 Filament winding 48
2.7.6 Pultrusion. 49
2.7.7 Sandwich construction 49
2.7.8 Adhesive bonding . 50
2.7.9 Prebond moisture . 52
2.8 CURE AND CONSOLIDATION PROCESSES 52
2.8.1 Vacuum bag molding .. 52
2.8.2 Oven cure . 53
2.8.3 Autoclave curing processing 53
2.8.3.1 General description 53
2.8.3.2 Sources of variability. 54
2.8.4 Press molding . 54
2.8.5 Integrally heated tooling. 54
2.8.6 Pultrusion die cure and consolidation. 55
2.8.7 Resin transfer molding (RTM). 55
2.8.8 Thermoforming .. 58
2.9 ASSEMBLY PROCESSES. 58
2.10 PROCESS CONTROL . 59
2.10.1 Common process control schemes . 59
2.10.1.1 Empirical methods . 59
2.10.1.2 Active sensor-based control . 59
2.10.1.3 Passive model-based control .. 59
2.10.2 Example - autoclave cure of a thermoset composite . 59
2.10.2.1 Degree of cure. 60
2.10.2.2 Viscosity.. 60
2.10.2.3 Resin pressure. 62
2.10.2.4 Void prevention 63
2.10.2.5 Flow .. 63
2.11 PREPARING MATERIAL AND PROCESSING SPECIFICATIONS .. 64
2.11.1 Types of specifications 64
2.11.1.1 Material specifications . 64
2.11.1.2 Process specs - controls end product . 64
2.11.2 Format for specifications 64
2.11.2.1 Scope 64
2.11.2.2 Applicable documents.. 64
2.11.2.3 Technical requirements/process controls .. 65
2.11.2.4 Receiving inspection and qualification testing. 65
2.11.2.5 Delivery 65
2.11.2.6 Notes 65
2.11.2.7 Approved sources and other 65
2.11.3 Specification examples .. 66
2.11.3.1 Industry 66
2.11.3.2 Military.. 66
2.11.4 Configuration management . 66
CHAPTER 3 QUALITY CONTROL OF PRODUCTION MATERIALS AND PROCESSES.. 1
3.1 INTRODUCTION.. 1
3.2 MATERIAL PROCUREMENT QUALITY ASSURANCE PROCEDURES. 1
3.2.1 Specifications and documentation .. 1
3.2.2 Receiving inspection.. 1
3.3 PART FABRICATION VERIFICATION 2
3.3.1 Process verification. 2
3.3.2 Nondestructive inspection 5
3.3.3 Destructive tests .. 6
3.3.3.1 Background.. 6
3.3.3.2 Usage . 6
3.3.3.3 Destructive test approaches 7
3.3.3.4 Implementation guidelines 7
3.3.3.5 Test types.. 8
3.4 STATISTICAL PROCESS CONTROL.8
3.4.1 Introduction . 8
3.4.2 Quality tools 8
3.4.3 Gathering and plotting data 8
3.4.4 Control charts. 8
3.4.5 Process capability 9
3.4.6 Troubleshooting and improvement . 9
3.4.6.1 Process feedback adjustment 9
3.4.6.2 Design of experiments ..11
3.4.6.3 Taguchi 20
3.4.7 Lot acceptance 20
3.5 MANAGING CHANGE IN MATERIALS AND PROCESSES 20
3.5.1 Introduction .. 20
3.5.2 Qualification of new materials or processes 20
3.5.2.1 Problem statement. 20
3.5.2.2 Business case.. 22
3.5.2.3 Divergence and risk .. 22
3.5.2.4 Technical acceptability. 22
3.5.2.5 Allowables development and equivalency validation .. 22
3.5.2.6 Production readiness 22
3.5.2.7 Lessons learned . 22
3.5.3 Divergence and risk . 22
3.5.3.1 Divergence. 24
3.5.3.2 Risk assessment. 25
3.5.3.3 Risk analysis. 26
3.5.4 Production readiness .. 26
CHAPTER 4 BUILDING BLOCK APPROACH FOR COMPOSITE STRUCTURES 1
4.1 INTRODUCTION AND PHILOSOPHY1
4.2 RATIONALE AND ASSUMPTIONS..4
4.3 METHODOLOGY. 5
4.3.1 General approach 5
4.4 CONSIDERATIONS FOR SPECIFIC APPLICATIONS..6
4.4.1 Aircraft for prototypes 6
4.4.1.1 PMC composite allowables generation for DOD/NASA prototype aircraft structure. 6
4.4.1.2 PMC composites building block structural development for DOD/NASA prototype aircraft .. 10
4.4.1.3 Summary of allowables and building block test efforts for DOD/NASA prototype composite aircraft structure .. 15
4.4.2 Aircraft for EMD and production 15
4.4.2.1 PMC composite allowables generation for DOD/NASA EMD and production aircraft structure.. 15
4.4.2.2 PMC composite building block structural development for DOD/NASA EMD and production aircraft .. 19
4.4.2.3 Summary of allowables and building block test efforts for DOD/NASA EMD and production composite aircraft structure 24
4.4.3 Commercial aircraft.. 24
4.4.3.1 Introduction 24
4.4.3.2 The building block approach. 24
4.4.3.2.1 Certification approaches .. 25
4.4.3.2.2 Allowables versus design values . 26
4.4.3.2.3 Lamina vs. laminate derived allowables for predicting strength .. 26
4.4.3.2.4 Product development . 27
4.4.3.3 Composite road map 27
4.4.3.3.1 Criteria 28
4.4.3.3.2 Regulations . 28
4.4.3.4 Commercial building block approach 29
4.4.3.5 Group A, material property development 29
4.4.3.5.1 Block 1 - material screening and selection . 30
4.4.3.5.2 Block 2 - material and process specification development. 30
4.4.3.5.3 Block 3 - allowables development .. 30
4.4.3.6 Group B, design-value development 31
4.4.3.6.1 Block 4 - structural element tests. 31
4.4.3.6.2 Block 5 - subcomponent tests 33
4.4.3.7 Group C, analysis verification.. 33
4.4.3.7.1 Block 6 - component test . 34
4.4.3.8 Boeing 777 aircraft composite primary structure building block approach. 34
4.4.3.8.1 Introduction . 34
4.4.3.8.2 Coupons and elements . 35
4.4.3.8.3 Subcomponents 36
4.4.3.8.4 Components 38
4.4.3.8.5 777 pre-production horizontal stabilizer test .. 38
4.4.3.8.6 Fin root attachment test 40
4.4.3.8.7 777 horizontal stabilizer tests. 40
4.4.3.8.8 777 vertical stabilizer test. 41
4.4.3.8.9 Future programs .. 41
4.4.4 Business and private aircraft .. 41
4.4.4.1 High performance .. 41
4.4.4.1.1 Introduction . 41
4.4.4.1.2 Typical building block program.. 42
4.4.4.2 Lightweight and kit . 46
4.4.5 Rotorcraft .. 46
4.4.5.1 Design allowables testing .. 48
4.4.5.1.1 Airframe. 48
4.4.5.1.2 Rotor system.. 48
4.4.5.1.3 Drive system .. 49
4.4.5.2 Design development testing . 50
4.4.5.2.1 Airframe. 50
4.4.5.2.2 Rotor system.. 51
4.4.5.2.3 Drive system .. 51
4.4.5.3 Full scale substantiation testing.. 52
4.4.5.3.1 Airframe. 53
4.4.5.3.2 Rotor system.. 53
4.4.5.3.3 Drive system .. 54
4.4.6 Spacecraft . 55
4.5 SPECIAL CONSIDERATION AND VARIANCES FOR SPECIFIC PROCESSES AND MATERIAL FORMS 55
4.5.1 Room Temperature .. 55
CHAPTER 5 DESIGN AND ANALYSIS 1
5.1 INTRODUCTION.. 1
5.2 BASIC LAMINA PROPERTIES AND MICROMECHANICS. 1
5.2.1 Assumptions .. 2
5.2.1.1 Material homogeneity . 2
5.2.1.2 Material orthotropy 2
5.2.1.3 Material linearity. 2
5.2.1.4 Residual stresses . 2
5.2.2 Fiber composites: physical properties .. 2
5.2.2.1 Elastic properties .. 3
5.2.2.2 Viscoelastic properties 7
5.2.2.3 Thermal expansion and moisture swelling .. 9
5.2.2.4 Thermal conduction and moisture diffusion.. 12
5.2.3 Fiber composites: strength and failure . 13
5.2.3.1 Axial tensile strength. 14
5.2.3.1.1 Weakest link failure. 14
5.2.3.1.2 Cumulative weakening failure 14
5.2.3.1.3 Fiber break propagation failure. 15
5.2.3.1.4 Cumulative group mode failure. 15
5.2.3.2 Axial compressive strength 15
5.2.3.3 Matrix mode strength 17
5.2.4 Strength under combined stress 17
5.2.5 Summary 21
5.3 ANALYSIS OF LAMINATES.. 21
5.3.1 Lamina stress-strain relations. 21
5.3.2 Lamination theory . 27
5.3.3 Laminate properties . 31
5.3.3.1 Membrane stresses .. 31
5.3.3.2 Bending 34
5.3.3.3 Thermal expansion 37
5.3.3.4 Moisture expansion 40
5.3.3.5 Conductivity .. 40
5.3.4 Thermal and hygroscopic analysis .. 41
5.3.4.1 Symmetric laminates 42
5.3.4.2 Unsymmetric laminates .. 43
5.3.5 Laminate stress analysis .. 43
5.3.5.1 Stresses due to mechanical loads . 43
5.3.5.2 Stresses due to temperature and moisture .. 44
5.3.5.3 Netting analysis .. 45
5.3.5.3.1 Netting analysis for design of filament wound pressure vessels . 46
5.3.5.4 Interlaminar stresses 49
5.3.5.5 Nonlinear stress analysis 49
5.3.6 Summary 49
5.4 LAMINATE STRENGTH AND FAILURE . 50
5.4.1 Sequential ply failure approach . 50
5.4.1.1 Initial ply.. 50
5.4.1.2 Subsequent failures.. 53
5.4.2 Fiber failure approach (laminate level failure) 53
5.4.3 Laminate design 55
5.4.4 Stress concentrations . 56
5.4.5 Delamination 59
5.4.5.1 Compression. 60
5.4.6 Damage and failure modes.. 61
5.4.6.1 Tension 61
5.4.6.1.1 Matrix cracks.. 62
5.4.6.2 Compression. 63
5.4.7 Summary 64
5.5 COMPLEX LOADS 65
5.5.1 Biaxial in-plane loads.. 65
5.5.2 Out-of-plane loads 65
5.6 LAMINA TO LAMINATE CONSIDERATIONS.. 65
5.6.1 Residual stresses and strains. 65
5.6.2 Thickness effects .. 65
5.6.3 Edge effects . 66
5.6.4 Effects of transverse tensile properties in unidirectional tape 67
5.6.5 Laminate stacking sequence effects 68
5.6.5.1 Introduction 68
5.6.5.2 Design guidelines .. 68
5.6.5.2.1 Strong recommendations . 69
5.6.5.2.2 Recommendations .. 70
5.6.6 Lamina-to-laminate statistics .. 71
5.6.7 Summary 71
5.7 COMPRESSIVE BUCKLING AND CRIPPLING . 71
5.7.1 Plate buckling and crippling. 71
5.7.1.1 Introduction 71
5.7.1.2 Initial buckling .. 72
5.7.1.3 Uniaxial loading - long plate with all sides simply supported .. 72
5.7.1.4 Uniaxial loading - long plate with all sides fixed . 74
5.7.1.5 Uniaxial loading - long plate with three sides simply supported and one unloaded edge free. 75
5.7.1.6 Uniaxial and biaxial loading - plate with all sides simply supported 75
5.7.1.7 Uniaxial loading - plate with loaded edges simply supported and unloaded edges fixed 76
5.7.1.8 Stacking sequence effects in buckling . 76
5.7.2 Compressive postbuckling and crippling .. 79
5.7.2.1 Analytical models 86
5.7.2.2 Fatigue effects . 88
5.7.2.3 Crippling curve determination.. 89
5.7.2.4 Stiffener crippling strength determination .. 89
5.7.2.5 Effects of corner radii and fillets.. 92
5.7.2.6 Slenderness correction 93
5.7.3 Summary 93
5.8 CARPET PLOTS. 93
5.9 CREEP AND RELAXATION.. 93
5.10 FATIGUE 94
5.11 VIBRATION 94
5.11.1 Introduction .. 94
5.11.2 Stacking sequence effects 94
5.12 OTHER STRUCTURAL PROPERTIES .. 94
5.13 COMPUTER PROGRAMS. 94
5.14 CERTIFICATION REQUIREMENTS. 94
CHAPTER 6 STRUCTURAL BEHAVIOR OF JOINTS 1
6.1 INTRODUCTION.. 1
6.2 ADHESIVE JOINTS . 2
6.2.1 Introduction . 2
6.2.2 Joint design considerations 3
6.2.2.1 Effects of adherend thickness: adherend failures vs. bond failures 3
6.2.2.2 Joint geometry effects. 4
6.2.2.3 Effects of adherend stiffness unbalance 5
6.2.2.4 Effects of ductile adhesive response .. 5
6.2.2.5 Behavior of composite adherends 7
6.2.2.6 Effects of bond defects .. 8
6.2.2.7 Durability of adhesive joints. 9
6.2.3 Stresses and structural behavior of adhesive joints .11
6.2.3.1 General .11
6.2.3.2 Adhesive shear stresses 12
6.2.3.3 Peel stresses 17
6.2.3.4 Single and double lap joints with uniform adherend thickness 19
6.2.3.4.1 Joint behavior with elastic response of the bond layer . 19
6.2.3.4.2 Thermal stress effects 29
6.2.3.4.3 Effect of ductility on joint stresses 31
6.2.3.4.4 Transverse shear and stacking sequence effects in composite adherends 34
6.2.3.5 Tapered and multi-step adherends 36
6.2.3.6 Finite element modeling . 46
6.2.4 Mechanical response of adhesives . 48
6.2.5 Mechanical response of composite adherends . 49
6.2.6 Adhesive joint conclusions 49
6.3 MECHANICALLY FASTENED JOINTS 49
6.3.1 Introduction .. 49
6.3.2 Structural analysis. 49
6.3.2.1 Load sharing in a joint.. 49
6.3.2.2 Analysis of local failure in bolted joints 51
6.3.2.3 Failure criteria .. 59
6.3.3 Design considerations 60
6.3.3.1 Geometry 60
6.3.3.2 Lay-up and stacking sequence 60
6.3.3.3 Fastener selection . 60
6.3.4 Fatigue.. 61
6.3.4.1 Influence of loading mode . 62
6.3.4.2 Influence of joint geometry 62
6.3.4.3 Influence of attachment details 63
6.3.4.4 Influence of laminate lay-up.. 63
6.3.4.5 Influence of environment 63
6.3.4.6 Influence of specimen thickness. 63
6.3.4.7 Residual strength 63
6.3.5 Test verification .. 64
CHAPTER 7 DAMAGE RESISTANCE, DURABILITY, AND DAMAGE TOLERANCE.. 1
7.1 OVERVIEW AND GENERAL GUIDELINES 1
7.1.1 Principles . 1
7.1.2 Composite-related issues 1
7.1.3 General guidelines.. 2
7.1.4 Section organization .. 4
7.2 AIRCRAFT DAMAGE TOLERANCE4
7.2.1 Evolving military and civil aviation requirements . 5
7.2.2 Methods of compliance to aviation regulations.. 10
7.2.2.1 Compliance with static strength requirements (civil aviation)11
7.2.2.2 Compliance with damage tolerance requirements (civil aviation) . 12
7.2.2.3 Deterministic compliance method (civil aviation example) 15
7.2.2.4 Probabilistic or semi-probabilistic compliance methods (civil aviation) .. 19
7.2.2.5 Comparison of deterministic and probabilistic methods . 24
7.2.2.6 Full-scale tests for proof of structure (civil aviation) . 25
7.3 TYPES, CHARACTERISTICS, AND SOURCES OF DAMAGE . 26
7.3.1 Damages characterized by stage of occurrence .. 27
7.3.1.1 Manufacturing .. 27
7.3.1.2 Service. 27
7.3.2 Damages characterized by physical imperfection 28
7.3.3 Realistic impact energy threats to aircraft. 30
7.4 INSPECTION FOR DAMAGE.. 33
7.4.1 Aircraft inspection programs 33
7.4.2 Recommendations for damage inspection data development .. 34
7.4.2.1 Goals 35
7.4.2.2 Inspection techniques.. 35
7.5 DAMAGE RESISTANCE. 36
7.5.1 Influencing factors. 36
7.5.1.1 Summary of results from previous impact studies. 37
7.5.1.2 Through-penetration impacts 38
7.5.1.3 Material type and form effects . 41
7.5.1.4 Depth of damage 43
7.5.1.5 Laminate thickness effects 43
7.5.1.6 Structural size effects 46
7.5.1.7 Sandwich structure 48
7.5.2 Design issues and guidelines . 50
7.5.2.1 Use of impact surveys for establishing critical damages 50
7.5.2.2 Structural arrangement and design details 50
7.5.2.3 Ground hail 51
7.5.2.4 Lightning . 51
7.5.2.5 Handling and step loads . 52
7.5.2.6 Exposed edges 52
7.5.3 Test issues 52
7.5.4 Analysis methods - description and assessment.. 52
7.6 DURABILITY (DAMAGE INITIATION) . 52
7.6.1 Introduction .. 52
7.6.2 Life factor approach . 53
7.6.3 Load enhancement factor approach 55
7.6.4 Ultimate strength approach.. 56
7.6.5 Spectrum truncation. 57
7.6.6 Durability certification.. 57
7.6.7 Influencing factors. 57
7.6.8 Design issues and guidelines . 57
7.6.9 Test issues 58
7.6.10 Analysis methods - description and assessment.. 58
7.7 DAMAGE GROWTH UNDER CYCLIC LOADING. 58
7.7.1 Influencing factors. 58
7.7.2 Design issues and guidelines . 60
7.7.3 Test issues 60
7.7.4 Analysis methods - description and assessment.. 60
7.7.4.1 Large through-penetration damage.. 60
7.7.4.2 Single delaminations and disbonds .. 60
7.7.4.2.1 Delamination growth .. 60
7.7.4.3 Impact damages . 60
7.7.4.4 Cuts and gouges. 60
7.8 RESIDUAL STRENGTH.. 61
7.8.1 Influencing Factors .. 61
7.8.1.1 Relationships between damage resistance and residual strength 61
7.8.1.2 Structure with impact damage . 61
7.8.1.2.1 Material effects.. 61
7.8.1.2.2 Interlaminar toughness effects.. 62
7.8.1.2.3 Stacking sequence effects .. 62
7.8.1.2.4 Laminate thickness effects.. 64
7.8.1.2.5 Through-thickness stitching 64
7.8.1.2.6 Sandwich structure . 64
7.8.1.2.7 Impact characteristic damage states . 64
7.8.1.2.8 Residual strength - compressive/shear loads.. 68
7.8.1.2.9 Residual strength - tensile loads. 69
7.8.1.2.10 Stiffened panels. 69
7.8.1.3 Structure with through-penetration damage . 71
7.8.1.3.1 Stitched skin/stiffener panels . 82
7.8.2 Design issues and guidelines . 82
7.8.2.1 Stacking sequences.. 82
7.8.2.2 Sandwich structure 82
7.8.3 Test issues 83
7.8.3.1 Impact tests on coupons. 83
7.8.3.2 Impact tests on stiffened panels . 83
7.8.3.3 Impact tests on sandwich panels 83
7.8.3.4 Tests for large through-penetration damage to stiffened panels 84
7.8.3.5 Tests for large through-penetration damage to sandwich panels.. 84
7.8.4 Analysis methods - description and assessment.. 84
7.8.4.1 Large through-penetration damage.. 84
7.8.4.1.1 Reduced singularity (Mar-Lin) model. 92
7.8.4.1.2 Strain softening laws 103
7.8.4.1.3 LEFM - based methods.. 109
7.8.4.1.4 R-curves..110
7.8.4.2 Single delaminations and disbonds .113
7.8.4.2.1 Fracture mechanics approaches.114
7.8.4.2.2 Sublaminate buckling methods114
7.8.4.3 Impact damages 115
7.8.4.3.1 Sublaminate buckling methods115
7.8.4.3.2 Strain softening methods 119
7.8.4.4 Cuts and gouges.. 121
7.9 APPLICATIONS/EXAMPLES. 121
7.9.1 Rotorcraft (Sikorsky) . 122
7.9.1.1 Damage 122
7.9.1.2 Environment 122
7.9.1.3 Test loading conditions related to critical failure modes .. 122
7.9.1.4 Test loads - load enhancement factor (LEF) . 122
7.9.1.5 Spectrum - truncation 123
7.9.1.6 Residual strength test 124
7.9.2 Commercial aircraft (Boeing 777 empennage torque boxes).. 124
7.9.2.1 Durability - environmental 124
7.9.2.2 Durability - mechanical loads. 125
7.9.2.3 Damage 125
7.9.2.4 Damage tolerance - "no growth" tests .. 125
7.9.2.5 Damage tolerance - residual strength .. 127
7.9.2.6 Inspection plan.. 127
7.9.3 General aviation (Raytheon Starship).. 127
7.9.3.1 Introduction . 127
7.9.3.2 Damage tolerance evaluation 128
7.9.3.2.1 Regulatory basis 128
7.9.3.2.2 Typical damage scenarios and related requirements . 128
7.9.3.2.3 Damage source and modes. 128
7.9.3.2.4 Element testing .. 129
7.9.3.2.5 Test results 130
7.9.3.2.6 Full scale tests 134
7.9.3.2.7 Continued airworthiness inspections .. 135
7.9.3.3 Service experience . 135
7.9.3.4 Conclusions 136
7.9.4 Military aircraft.. 136
CHAPTER 8 SUPPORTABILITY. 1
8.1 INTRODUCTION.. 1
8.2 DESIGN FOR SUPPORTABILITY 2
8.2.1 In-service experience. 2
8.2.2 Inspectability .. 5
8.2.2.1 General design guidelines 5
8.2.2.2 Accessibility for inspection 7
8.2.3 Material selection. 7
8.2.3.1 Introduction .. 7
8.2.3.2 Resins and fibers .. 7
8.2.3.3 Product forms . 9
8.2.3.4 Adhesives . 9
8.2.3.5 Supportability issues 9
8.2.3.6 Environmental concerns 9
8.2.4 Damage resistance, damage tolerance, and durability ..11
8.2.4.1 Damage resistance.11
8.2.4.2 Damage tolerance . 12
8.2.4.3 Durability. 12
8.2.5 Environmental compliance 13
8.2.5.1 Elimination/reduction of heavy metals . 13
8.2.5.2 Consideration of paint removal requirements.. 13
8.2.5.3 Shelf life and storage stability of repair materials .. 13
8.2.5.4 Cleaning requirements. 14
8.2.5.5 Non-destructive inspection requirements .. 14
8.2.5.6 End of life disposal considerations 14
8.2.6 Reliability and maintainability.. 14
8.2.7 Interchangeability and replaceability .. 15
8.2.8 Accessibility . 15
8.2.9 Repairability . 15
8.2.9.1 General design approach .. 16
8.2.9.2 Repair design issues 19
8.3 SUPPORT IMPLEMENTATION .. 20
8.3.1 Part Inspection 20
8.3.1.1 Visual 21
8.3.1.2 Tap testing . 22
8.3.1.3 Ultrasonics . 22
8.3.1.4 Radiography . 24
8.3.1.5 Shearography .. 25
8.3.1.6 Thermography . 25
8.3.2 Damage assessment for composite repairs 26
8.3.2.1 General 26
8.3.2.2 Mandate of the assessor 27
8.3.2.3 Qualification of the assessor 27
8.3.2.4 Information for damage assessment 27
8.3.2.5 Dependence on repair location 28
8.3.3 Repair design criteria .. 29
8.3.3.1 Part stiffness . 30
8.3.3.2 Static strength and stability 30
8.3.3.3 Durability. 31
8.3.3.4 Damage tolerance . 31
8.3.3.5 Related aircraft systems . 31
8.3.3.6 Aerodynamic smoothness . 32
8.3.3.7 Weight and balance .. 32
8.3.3.8 Operating temperatures.. 32
8.3.3.9 Environment.. 32
8.3.3.10 Surrounding structure .. 33
8.3.3.11 Temporary repair. 33
8.3.4 Repair of composite structures.. 34
8.3.4.1 Introduction 34
8.3.4.2 Damage removal and site preparation 34
8.3.4.3 Bolted repairs 35
8.3.4.3.1 Repair concepts 35
8.3.4.3.2 Repair materials 37
8.3.4.3.3 Repair analysis.. 37
8.3.4.3.4 Repair procedures 38
8.3.4.3.5 Example of a bolted repair .. 39
8.3.4.4 Bonded repairs 39
8.3.4.4.1 Repair concepts 39
8.3.4.4.2 Repair materials 41
8.3.4.4.3 Repair analysis.. 42
8.3.4.4.4 Repair procedures 43
8.3.4.4.5 Bonded repair examples .. 46
8.3.4.5 Sandwich (honeycomb) repairs .. 47
8.3.4.5.1 Repair concepts 47
8.3.4.5.2 Core restoration 48
8.3.4.5.3 Repair procedures 50
8.3.4.5.4 Sandwich repair example. 50
8.3.4.6 Repair inspection 51
8.3.4.6.1 In-process quality control . 51
8.3.4.6.2 Post-process inspection 51
8.3.4.7 Repair validation . 51
8.4 COMPOSITE REPAIR OF METAL STRUCTURE (CRMS) .. 52
8.5 LOGISTICS REQUIREMENTS 53
8.5.1 Training .. 53
8.5.2 Spares 54
8.5.3 Materials 54
8.5.4 Facilities . 55
8.5.5 Technical data . 56
8.5.6 Support equipment .. 56
8.5.6.1 Curing equipment .. 56
8.5.6.2 Cold storage rooms .. 57
8.5.6.3 Sanding/grinding booths. 58
8.5.6.4 NDI equipment. 58
CHAPTER 9 STRUCTURAL RELIABILITY.. 1
9.1 INTRODUCTION.. 1
9.2 FACTORS AFFECTING STRUCTURAL RELIABILITY . 1
9.2.1 Static strength 1
9.2.2 Environmental effects 2
9.2.3 Fatigue. 2
9.2.4 Damage tolerance .. 3
9.3 RELIABILITY ENGINEERING. 3
9.4 RELIABILITY DESIGN CONSIDERATIONS 4
9.5 RELIABILITY ASSESSMENT AND DESIGN .. 5
9.5.1 Background 5
9.5.2 Deterministic vs. Probabilistic Design Approach . 6
9.5.3 Probabilistic Design Methodology .. 7
9.5.4 Data Requirements. 8
9.5.5 Summary. 8
9.6 RELIABILITY BASED STRUCTURAL QUALIFICATION 10
9.6.1 Analysis. 10
9.6.2 Testing 10
9.7 LIFE CYCLE REALIZATION . 10
9.7.1 Manufacturing . 10
9.7.2 Operational .. 10
CHAPTER 10 THICK-SECTION COMPOSITES .. 1
10.1 INTRODUCTION AND DEFINITION OF THICK-SECTION. 1
10.2 MECHANICAL PROPERTIES REQUIRED FOR THICK-SECTION COMPOSITE THREE DIMENSIONAL ANALYSIS .. 2
10.2.1 2-D composite analysis. 3
10.2.2 3-D composite analysis. 3
10.2.2.1 Unidirectional lamina 3-D properties .. 4
10.2.2.2 Oriented orthotropic laminate 3-D properties . 4
10.2.3 Experimental property determination. 5
10.2.3.1 Uniaxial tests .. 6
10.2.3.2 Multiaxial tests . 16
10.2.3.2.1 Lineal test specimens/techniques 19
10.2.3.2.2 Cylindrical test specimens/techniques.. 20
10.2.4 Theoretical property determination.. 21
10.2.4.1 3-D lamina property determination 21
10.2.4.2 3-D laminate property determination 22
10.2.5 Test specimen design considerations. 29
10.3 STRUCTURAL ANALYSIS METHODS FOR THICK-SECTION COMPOSITES 29
10.4 PHYSICAL PROPERTY ANALYSIS REQUIRED FOR THICK-SECTION COMPOSITE
THREE-DIMENSIONAL ANALYSIS..29
10.5 PROCESS ANALYSIS METHODS FOR THICK-SECTION COMPOSITES 29
10.6 FAILURE CRITERIA . 29
10.7 FACTORS INFLUENCING THICK-SECTION ALLOWABLES (I.E., SAFETY MARGINS) 29
10.8 THICK LAMINATE DEMONSTRATION PROBLEM . 29
CHAPTER 11 ENVIRONMENTAL MANAGEMENT 1
11.1 INTRODUCTION.. 1
11.1.1 Scope 1
11.1.2 Glossary of recycling terms 1
11.2 RECYCLING INFRASTRUCTURE.. 4
11.2.1 Recycling infrastructure development models.. 4
11.2.2 Infrastructure needs 4
11.2.3 Recycling education 5
711.3 ECONOMICS OF COMPOSITE RECYCLING .. 5
11.4 COMPOSITE WASTE STREAMS 6
11.4.1 Process waste .. 7
11.4.2 Post consumer composite waste. 8
11.5 COMPOSITE WASTE STREAM SOURCE REDUCTION 8
11.5.1 Just-in-time and just enough material delivery . 8
11.5.2 Electronic commerce acquisition management 9
11.5.3 Waste minimization guidelines . 9
11.5.3.1 Prepreg .. 9
11.5.3.2 Resin 9
11.5.3.3 Fiber. 9
11.5.3.4 Curing agents . 9
11.5.3.5 Autoclaving materials.. 9
11.5.3.6 Packaging materials . 10
11.5.4 Lightweighting. 10
11.6 REUSE OF COMPOSITE COMPONENTS AND MATERIALS 10
11.6.1 Reuse of composite components . 10
11.6.2 Machining to smaller components 10
11.7 MATERIALS EXCHANGE.. 10
11.7.1 Reallocation of precursors .11
11.7.2 Composite materials exchange services 11
11.7.2.1 Care of unused materials 11
11.7.2.2 Packaging 11
11.7.2.3 Documentation of care..11
11.7.2.4 Description of unused materials ..11
11.7.2.5 DOD resale restrictions.11
11.8 RECYCLING OF COMPOSITE MATERIALS .. 12
11.8.1 Design for disassembly and recycling 12
11.8.1.1 Fasteners 12
11.8.1.2 Adhesives .. 12
11.8.1.3 Hybrid composites . 12
11.8.2 Recycling logistics 12
11.8.2.1 Collection and transportation 13
11.8.2.2 Identification of fibers and matrices.. 13
11.8.2.2.1 Fourier transform infrared spectroscopy.. 13
11.8.2.2.2 Densitometry.. 13
11.8.2.2.3 Coding of components .. 14
11.8.2.2.4 Routing of waste streams 14
11.8.3 Processing of composite recyclate .. 14
11.8.3.1 Size reduction .. 14
11.8.3.2 Matrix removal . 14
11.8.3.3 Fiber reuse. 15
11.8.3.4 Products of matrix removal 15
11.8.3.5 Other recycling and processing methods .. 15
11.8.4 Recycling of waste prepreg . 16
CHAPTER 12 LESSONS LEARNED .. 1
12.1 INTRODUCTION.. 1
12.2 UNIQUE ISSUES FOR COMPOSITES . 1
12.2.1 Elastic properties . 1
12.2.2 Tailored properties and out-of-plane loads . 2
12.2.3 Damage tolerance .. 4
12.2.4 Durability. 4
12.2.5 Environmental sensitivity . 5
12.2.6 Joints. 6
12.2.6.1 Mechanically-fastened joints .. 6
12.2.6.2 Problems associated with adhesive bonding to peel-ply composite surfaces.. 6
12.2.7 Design.. 8
12.2.8 Handling and storage. 9
12.2.9 Processing and fabrication . 9
12.2.9.1 Quality control.. 10
12.3 LESSONS LEARNED 11
12.3.1 Design and analysis..11
12.3.1.1 Sandwich design. 14
12.3.1.2 Bolted joints .. 15
12.3.1.3 Bonded joints 18
12.3.1.4 Composite to metal splice joints . 20
12.3.1.5 Composite to metal continuous joints.. 21
12.3.1.6 Composite to composite splice joints .. 21
12.3.2 Materials and processes 21
12.3.3 Fabrication and assembly. 22
12.3.4 Quality control . 24
12.3.5 Testing 25
12.3.6 Certification. 26
12.3.7 In-service and repair 26
INDEX.. I-1