Polymer Composites in the Aerospace Industry (Woodhead Publishing Series in Composites Science and Engineering)

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Polymer Composites in the Aerospace Industry
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Contributors
Preface
Part One: Design and manufacture of composite components for aerospace structures
1 - Aerospace engineering requirements in building with composites
	1.1 Introduction
		1.1.1 Carbon fiber types and properties
		1.1.2 Fiber-matrix interface
		1.1.3 Resin materials
	1.2 Analysis and design
	1.3 Manufacturing techniques
	1.4 Applications in aircraft construction
	1.5 Conclusion
	References
	Further reading
2 - Modeling of 2D and 3D woven composites
	2.1 Introduction
	2.2 Architecture of a woven unit cell
		2.2.1 2D and 3D weave topology and geometry
		2.2.2 Geometrical model: yarn volumes
		2.2.3 Transformation of the geometry into FE model
			2.2.3.1 Geometrical challenges
			2.2.3.2 Overview of 3D meso-FE models
			2.2.3.3 Paths forward
			2.2.3.4 Specifics of finite element modeling of textile composites
	2.3 Stiffness modeling: method of inclusions
		2.3.1 Analytical approaches to stiffness calculations
		2.3.2 Method of inclusions and Mori-Tanaka homogenization
		2.3.3 Example: 3D angle interlock composites
	2.4 Stress and strength modeling: FE analysis
		2.4.1 Stress modeling
		2.4.2 Specifics of damage accumulation in textile composites
		2.4.3 Local stiffness degradation and damage evolution law
		2.4.4 An example of failure modeling
	2.5 Conclusions
	References
3 - Manufacturing processes for composite materials and components for aerospace applications
	3.1 Introduction
	3.2 Key property and process requirements
	3.3 Prepreg/autoclave processes
	3.4 Filament winding
	3.5 Automated prepreg processes: automated fiber placement and automated tape layup
	3.6 Resin-infusion processes
		3.6.1 Manual layup and sprayup techniques
		3.6.2 Matched-die molding
		3.6.3 VARI molding
		3.6.4 RTM
		3.6.5 Variants of VARI and RTM processes
		3.6.6 Pultrusion
	3.7 Process monitoring
	3.8 Conclusions
	References
4 - Manufacturing defects in composites and their effects on performance
	4.1 Introduction
	4.2 Defects in composite materials
	4.3 Modeling with defects
	4.4 Implications for cost-effective manufacturing
	4.5 Mechanics-based analysis of defects
		4.5.1 Effect of voids on effective elastic properties
		4.5.2 Effect of voids on delamination growth
		4.5.3 Effect of defects on progressive intralaminar cracking
	4.6 Summary
	References
Part Two: Composite performance in aerospace structural design
5 - Buckling and compressive strength of laminates with optimized fiber-steering and layer-stacking for aerospace applications
	5.1 Introduction
	5.2 Elastic properties of laminates
	5.3 Buckling analysis
	5.4 Buckling optimization of straight fiber laminates
	5.5 Variable angle fibers using continuous tow shearing
	5.6 Compression after impact and damage tolerance
	5.7 Conclusion
	Glossary
	References
	Further reading
6 - Postbuckling analysis and optimization of laminated composite plates with applications in aerospace
	6.1 Introduction
	6.2 Fundamental theory
		6.2.1 Constitutive equations of composite laminates
		6.2.2 Governing equations
	6.3 Postbuckling analysis
		6.3.1 Asymptotic closed-form solutions
		6.3.2 Semi-analytical model based on a mixed variational principle
		6.3.3 Postbuckling stiffness indices
	6.4 Two-level postbuckling optimization of composite structures based on lamination parameters
		6.4.1 Two-level optimization framework
			6.4.1.1 Optimization criteria
			6.4.1.2 Feasible region of lamination parameters
			6.4.1.3 Two-level optimization
				First-level optimization
				Second-level optimization
		6.4.2 Postbuckling optimization of straight-fiber composite laminates
		6.4.3 Postbuckling optimization of variable angle tow composite laminates
		6.4.4 Postbuckling optimization of variable thickness, variable angle tow composite laminates, toward “buckle-design” concept
	References
7 - Stiffness & strength of composite structural elements
	7.1 Introduction
	7.2 Definition of structural elements
	7.3 Modeling approaches
		7.3.1 The single-ply coordinate system
		7.3.2 The laminate coordinate system
		7.3.3 Laminate stiffness
			7.3.3.1 Force and moment resultants
			7.3.3.2 Special classes of laminates
		7.3.4 The use of lamination parameters to define laminate stiffnesses
		7.3.5 Ply strength
			7.3.5.1 Failure modes
			7.3.5.2 Linear stress-strain response
		7.3.6 Laminate strength theories
			7.3.6.1 Typical failure analysis procedures
			7.3.6.2 First-ply failure theories
				7.3.6.2.1 Maximum stress
				7.3.6.2.2 Maximum strain
				7.3.6.2.3 Tsai-Hill
				7.3.6.2.4 Tsai-Wu
				7.3.6.2.5 Other failure criteria
				7.3.6.2.6 The Puck criterion
				7.3.6.2.7 LaRC 03 failure criterion
				7.3.6.2.8 Onset Failure Theory (originally Strain Invariant Failure Theory)
				7.3.6.2.9 First-ply failure using lamination parameters
		7.3.7 Notched strength of composite laminates
			7.3.7.1 The effect of a hole on laminate strength
			7.3.7.2 Alternative methods to predict final failure of laminate with a hole
	7.4 Woven composite materials
		7.4.1 Stiffness models
		7.4.2 Strength models
		7.4.3 The effect of flaws on the strength of woven fabrics
	7.5 Modeling effect of anomalies
		7.5.1 Porosity
		7.5.2 Larger voids as delaminations
	7.6 Future trends
		7.6.1 Trends in failure analysis
		7.6.2 New design concepts
			7.6.2.1 Grid-stiffened structures
			7.6.2.2 Variable stiffness laminates
			7.6.2.3 AP-PLY laminates
	References
	Sources of further information and advice
	Appendix 1: Glossary
8 - Fracture mechanics of polymer composites in aerospace applications
	8.1 Introduction and overview
	8.2 Applications of fracture mechanics to FRP composites used in aerospace
	8.3 Fracture mechanics test methods for FRP composites
		8.3.1 Quasi-static test methods
		8.3.2 Cyclic test methods
		8.3.3 High-rate test methods
	8.4 Fracture mechanics test data for selected FRP composites
	8.5 Fracture mechanics testing of non-unidirectional FRP composites
	8.6 Fracture mechanics simulation and modeling approaches for FRP composites
	8.7 Fracture mechanics testing under aerospace environmental conditions
	8.8 Conclusions and outlook
	Appendix: glossary
	Acknowledgments
	References
9 - The response of aerospace composites to temperature and humidity
	9.1 Introduction
		9.1.1 Moisture absorption
		9.1.2 Fickian diffusion
		9.1.3 Prediction of moisture content and time dependence
		9.1.4 Moisture distribution in a laminate
		9.1.5 Interfacial stability during moisture absorption
	9.2 Moisture sensitivity of matrix resins
		9.2.1 Epoxy resins
		9.2.2 Advanced matrix resins
	9.3 Mechanism of moisture retention in aerospace epoxies
		9.3.1 Chemical aspects
		9.3.2 Predictive modeling
	9.4 Anomalous effects
		9.4.1 Role of impurities and unreacted resin components
	9.5 Thermal spiking
	9.6 Thermo-mechanical response of resins
	9.7 Effect of moisture on composite performance
		9.7.1 Thermal stresses
		9.7.2 Thermal cracking
		9.7.3 Effect of moisture absorption
	9.8 Fiber-dominated properties
		9.8.1 Carbon fibers
		9.8.2 Advanced polymer fibers
		9.8.3 Glass fibers
			9.8.3.1 Thermal effects
			9.8.3.2 Environmental stress corrosion cracking (ESCC) of glass fibers
	9.9 Non-aqueous environments
	9.10 Composite unidirectional properties
		9.10.1 Tensile strength
		9.10.2 Compressive strength
	9.11 Conclusions
	References
10. Fatigue of polymer composites
	10.1 Introduction
	10.2 Construction of FLDs
	10.3 Modeling of FLD trends
	10.4 Fatigue of laminates
	10.5 Concluding remarks
	References
11 - Impact, post-impact strength, and post-impact fatigue behavior of polymer composites
	11.1 Introduction
	11.2 Nature of impact damage
	11.3 Residual strength after impact: observations
	11.4 Residual strength and damage extent after impact: predictive models
		11.4.1 Simple analytical approach
		11.4.2 Numerical techniques to predict impact damage extent and CAI strength
	11.5 Post impact fatigue behavior of polymer composite laminates
		11.5.1 General
		11.5.2 In-plane fatigue life of impacted composites
		11.5.3 Fatigue delamination growth from impact damage
	11.6 The damage-resistant structure: designing against impact and fatigue
		11.6.1 Resistance to impact
		11.6.2 Resistance to fatigue delamination growth
	11.7 Conclusions
	11.8 Future trends
	References
12 - Design and failure analysis of composite bolted joints for aerospace composites
	12.1 Introduction
		12.1.1 General overview of composite joint design
		12.1.2 Terminology used in bolted joint design
		12.1.3 Bolted joints failure modes
		12.1.4 Problem description
			12.1.4.1 Joint geometries
			12.1.4.2 Materials
			12.1.4.3 Bolt-hole clearance
	12.2 Finite element model
	12.3 Analysis of single-bolt joints
		12.3.1 Effects of bolt-hole clearance
		12.3.2 Effects of friction
		12.3.3 3D stress analysis in protruding-head joints
	12.4 Analysis of multibolt joints
		12.4.1 Bolt-load distribution in joints
		12.4.2 Failure prediction using bearing-bypass diagrams
		12.4.3 Modeling large joint assemblies
		12.4.4 Load distribution in large joint assemblies and effects of missing fasteners
	12.5 Failure analysis of joints
		12.5.1 Progressive damage analysis
		12.5.2 Damage modeling in multibolt joints
		12.5.3 Load-redistribution after bearing failure in multibolt joints
		12.5.4 Progression of damage in multibolt joints
			12.5.4.1 Damage progression in the C1_C1_C1 joint
			12.5.4.2 Damage progression in the C3_C3_C1 joint
	12.6 Future trends
	12.7 Conclusions
	12.8 Further sources of information
		12.8.1 Conferences
		12.8.2 Websites
		12.8.3 Interest groups and industries
		12.8.4 International journals and books
	References
	Further reading
13 - Design and testing of crashworthy aerospace composite components
	13.1 Introduction
	13.2 Crashworthy design concepts for aircraft structures
		13.2.1 Design philosophy and requirements for airframe crash resistance
		13.2.2 Use of composites in crashworthy subfloor structures
	13.3 Design of composite structural elements under crash loads
		13.3.1 Energy-absorbing mechanisms in composite structural elements
		13.3.2 Composites damage and delamination models
		13.3.3 Design analysis of crash elements
			13.3.3.1 DLR crush segments
			13.3.3.2 EA web segment
	13.4 Design and crash test of composite helicopter frame structure
		13.4.1 Frame structure design concept
		13.4.2 Quasi-static and crash test results
		13.4.3 Crash modeling and damage prediction
		13.4.4 Retrofit helicopter subfloor crash structure
	13.5 Future trends in damage and crash modeling
	13.6 Concluding remarks
	Acknowledgments
	References
14 - The blast response of composite and fiber-metal laminate materials
	14.1 Introduction
	14.2 Characteristics of explosions in the air
	14.3 Paradigms of blast protection
	14.4 Explosion loading of fuselage structures
	14.5 The blast performance of plain composites
	14.6 The blast performance of multilayered systems
		14.6.1 Composite sandwich panels
		14.6.2 Fiber-metal laminates
	14.7 Conclusions
	References
15 - Repair of damaged aerospace composite structures
	15.1 Introduction
	15.2 Assessment of repair and nondestructive tests
		15.2.1 Damage scenario
	15.3 Repair
		15.3.1 Resin injection
		15.3.2 Chopped fiber
		15.3.3 Bonded patch repair
		15.3.4 Honeycomb
	15.4 Typical repair procedure
		15.4.1 Bolted patch repair schemes
		15.4.2 Bonded versus bolted
	15.5 Analysis of repair
		15.5.1 Analysis of bolted repair
	15.6 Conclusion and future trends
	References
16 - Nondestructive testing of aerospace composites
	16.1 Introduction
	16.2 NDT, NDI, and NDE methods for polymer composite structures
		16.2.1 Quality assurance and NDT
	16.3 Probability of detection
	16.4 Visual and tap testing
	16.5 Ultrasonic testing
		16.5.1 UT methods
	16.6 Thermography
	16.7 Shearography
	16.8 Radiography
	16.9 Electromagnetic methods
	16.10 Bond inspection
	16.11 Summary and conclusions
	16.12 Future trends
	References
17 - Structural health monitoring (SHM) of aerospace composites
	17.1 Introduction
	17.2 Composite damage
		17.2.1 Tension damage in composites
		17.2.2 Compression damage in composites
		17.2.3 Fastener hole damage in composites
		17.2.4 Impact damage in composites
		17.2.5 Fatigue damage of composites
		17.2.6 Damage in composite sandwich structures
		17.2.7 Damage in adhesive composite joints
	17.3 SHM sensors
		17.3.1 Resistance strain gages
		17.3.2 Fiber optic sensors
		17.3.3 Fiber Bragg grating (FBG) sensors
		17.3.4 Piezoelectric wafer active sensors (PWAS)
		17.3.5 Travelling-wave SHM methods with PWAS transducers
		17.3.6 Standing-wave SHM methods with PWAS transducers
		17.3.7 Phased PWAS arrays and embedded ultrasonic structural radar
		17.3.8 Electrical properties sensors
	17.4 SHM methods and systems
		17.4.1 Strain monitoring as passive SHM method
		17.4.2 Impact monitoring as passive SHM method
		17.4.3 Acoustic emission monitoring as passive SHM method
		17.4.4 Acousto-ultrasonics active SHM method
		17.4.5 Vibration monitoring active SHM method
		17.4.6 Frequency transfer function active SHM method
		17.4.7 Electromechanical impedance spectroscopy active SHM method
		17.4.8 Electrical properties monitoring active SHM method
		17.4.9 Direct methods for impact damage detection
	17.5 Summary, conclusions, and suggestions for further work
	References
Part Three: Aerospace applications
18 - Lightning strike direct effects
	18.1 Introduction to lightning
	18.2 Aircraft and lightning
	18.3 Composite material and lightning
	18.4 Lightning loading mechanisms
	18.5 Composite material damage due to lightning
	18.6 Lightning experimental testing
		18.6.1 Standard test methods and aircraft protection design
		18.6.2 Special test methods
		18.6.3 Experimentally derived relationships
	18.7 Lightning protection systems
	18.8 Modeling for a lightning strike on aerospace composites
		18.8.1 Modeling specimen thermal behavior
		18.8.2 Modeling specimen pressure loading
		18.8.3 Modeling specimen explosive and thermal expansion loading
		18.8.4 Modeling lightning plasma
	18.9 Modeling enabled LPS design
	18.10 Outstanding challenges requiring further research
	Acknowledgments
	References
19 - Certification and airworthiness of polymer composite aircraft
	19.1 Introduction
	19.2 The regulators, regulations, and certification
	19.3 Certification of composite aircraft
		19.3.1 Initial airworthiness
		19.3.2 Residual strength (RS), fatigue and damage tolerance (F&DT)
		19.3.3 Building-block approach
		19.3.4 Structural bonding
		19.3.5 Accidental impact damage
		19.3.6 Initial airworthiness—continued airworthiness and maintenance
		19.3.7 Inspection and damage detection
			19.3.7.1 Visual inspection
		19.3.8 Continued airworthiness
			19.3.8.1 Ground impact damage and high-energy wide-area blunt impact (HEWABI)
		19.3.9 Product changes (repairs outside existing data limits and modifications)
	19.4 Other considerations
		19.4.1 Crashworthiness
		19.4.2 Thermal issues, fire protection, and flammability
		19.4.3 Lightning
		19.4.4 Workforce knowledge, training, and teamwork
		19.4.5 Reporting, forensics, and database taxonomy
	19.5 The future certification and airworthiness of polymer composite aircraft
	Appendix 1: The regulators, regulations, and certification
		A1.1 The regulators and the regulations
		A1.2 Certification
		A1.3 Product change and repairs
	Appendix 2: Glossary of terms, acronyms, and abbreviations
		Abbreviations & acronyms
	References
Index
	A
	B
	C
	D
	E
	F
	G
	H
	I
	J
	K
	M
	N
	O
	P
	Q
	R
	S
	T
	U
	V
	W
	X
	Y
	Z
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