Advances in Thick Section Composite and Sandwich Structures: An Anthology of ONR-sponsored Research

Preface
Acknowledgment
Contents
Contributors
Dynamic Response of Composite Structures in Extreme Loading Environments
	1 Introduction
	2 Response of Composite and Sandwich Structures to Air-Blast Loading
		2.1 Experimental Methods: The Shock Tube Facility
		2.2 Theoretical Considerations
			2.2.1 Preliminary Considerations
			2.2.2 Model by Wang et al
			2.2.3 Application of the Model by Wang et al. to Sandwich Composite Structures of Varying Areal Density
		2.3 Air Blast Response of Composite Sandwich Structures
			2.3.1 Effect of Functional Foam Core Gradation
				2.3.1.1 Deflection
				2.3.1.2 DIC Analysis
				2.3.1.3 Damage Mechanisms
		2.4 Air Blast Response of Composite Structures With Polyurea Coatings
			2.4.1 Effect of Polyurea on Composite Plates
				2.4.1.1 Center Point Deflection
				2.4.1.2 Failure Mechanisms
			2.4.2 Effect of Polyurea Location Within Composite Sandwich Structures
				2.4.2.1 Interface Deflection
				2.4.2.2 DIC Analysis
				2.4.2.3 Failure Mechanisms
	3 Response of Composite and Sandwich Structures to Extreme Underwater Loading Environments
		3.1 Experimental Methods: Free-Field Implosion
		3.2 Hydrostatic and Shock Initiated Implosion of Thin Cylindrical Composite Shells in Free-Field Environment
			3.2.1 Hydrostatic Implosion of Thin Cylindrical Carbon Composite Shells
				3.2.1.1 Deformation and Post-buckling Analysis
			3.2.2 Hydrostatic Implosion of Thin Cylindrical Glass Fiber Composite Shells
				3.2.2.1 Deformation and Post-buckling Analysis
			3.2.3 Shock-Initiated Buckling of Carbon/Epoxy Composite Tubes at Sub-Critical Pressures
		3.3 Mitigation of Pressure Pulses from Implosion of Thin Composite Shells
		3.4 Hydrostatic and Shock-Initiated Instabilities in Double-Hull Composite Cylinders
			3.4.1 Collapse Pressure
			3.4.2 Implosion Under Hydrostatic Pressure: Observed Collapse Behaviors
				3.4.2.1 Complete Collapse With Dwell
			3.4.3 Implosion Under Hydrostatic Pressure: Impulse and Energy
			3.4.4 Implosion Under Combined Hydrostatic and Shock Initiated Loadings: Pressure History
	References
The Response of Composite Materials Subjected to Underwater Explosive Loading: Experimental and Computational Studies
	1 Introduction
	2 Far Field UNDEX Loading of Curved Plates
		2.1 Conical Shock Tube Facility and Experimental Method
		2.2 Materials and Plate Geometry
		2.3 Computational (Finite Element) Model Overview
		2.4 Simulation Results and Correlation to Experiments
		2.5 Key Findings
	3 Near Field UNDEX Flat Plates
		3.1 Materials and Plate Configurations
		3.2 UNDEX Facility and Experimental Method
		3.3 Computational Model
		3.4 Experimental and Numerical Results
		3.5 Significant Findings
	4 Near Field UNDEX of Cylinders
		4.1 Cylinder Specimens
		4.2 Experimental Method
		4.3 Key Experimental Results and Findings
			4.3.1 Bubble-Cylinder Interaction and Local Pressures
			4.3.2 Transient Cylinder Response
			4.3.3 Material Damage
		4.4 Computational Model Overview
		4.5 Significant Computational Results and Findings
			4.5.1 Material Energy Comparisons
			4.5.2 Strain Comparison
		4.6 Results and Findings
	5 Weathering and Ageing Effects
		5.1 Accelerated Ageing Method
		5.2 Material Summary
		5.3 Underwater Blast Experiments
		5.4 Experimental Results
		5.5 Significant Findings
	6 Conclusion
	References
Blast Performance of Composite Sandwich Panels
	1 Introduction
	2 Air Blast Loading of Composite Sandwich Panels
		2.1 Experimental Design
			2.1.1 Effect of Core Thickness
			2.1.2 Effect of Core Material and Core Density
			2.1.3 Effect of Skin Configuration
			2.1.4 Effect of Progressive Loading and Multiple Blast
		2.2 Results
			2.2.1 Effect of Core Thickness
			2.2.2 Effect of Core Material and Core Density
			2.2.3 Effect of Skin Configuration
			2.2.4 Effect of Progressive Loading and Multiple Blast
		2.3 Discussion
			2.3.1 Effect of Core Thickness
			2.3.2 Effect of Core Material and Core Density
			2.3.3 Effect of Skin Configuration
			2.3.4 Effect of Progressive Loading and Multiple Blast
	3 Underwater Blast Loading of Composite Sandwich Panels
		3.1 Experimental Design
			3.1.1 Effect of Backing Medium
			3.1.2 Effect of Graded Core
			3.1.3 Effect of Skin Configuration
		3.2 Results
			3.2.1 Effect of Backing Medium
			3.2.2 Effect of Graded Core
			3.2.3 Effect of Skin Configuration
		3.3 Discussion
	4 Finite Element Analysis
		4.1 Air Blast Modeling Method
			4.1.1 The Effect of Support Conditions
			4.1.2 The Effect of Core Thickness
			4.1.3 The Effect of Skin Configuration
		4.2 Air Blast Modeling Results
			4.2.1 The Effect of Support Conditions
			4.2.2 The Effect of Core Thickness
			4.2.3 The Effect of Skin Configuration
		4.3 Discussion
	5 Conclusion
	References
Explosive Blast Response of Marine Sandwich Composites
	1 Introduction
	2 Sandwich Composite Materials and Experimental Methodology
		2.1 Fabrication of Sandwich Composite Materials
		2.2 Explosive Blast Testing of Sandwich Composite Materials
		2.3 Mechanical Property Testing of Sandwich Composite Materials
	3 Results and Discussion
		3.1 Blast-Induced Deformation of Sandwich Composite Materials
		3.2 Blast-Induced Damage to Sandwich Composite Materials
	4 Conclusion
	References
Dynamic Response of Polymers Subjected to Underwater Shock Loading or Direct Impact
	1 Introduction
	2 Underwater Explosions and Shock Wave Focusing in Convergent Structures
	3 Dynamic Fracture Behavior of Polymeric Materials
		3.1 Mode-I Dynamic Fracture Behavior of Poly (Methyl Methacrylate)
		3.2 Mode-I Dynamic Fracture Behavior of Carbon Fiber Vinyl Ester
		3.3 Mode-II Dynamic Fracture Behavior of Carbon Fiber Epoxy
	4 Conclusion
	References
Recent Developments on Ballistic Performance of Composite Materials of Naval Relevance
	1 Introduction
	2 Materials
	3 Experimental Program
		3.1 Impact Test Set-up
		3.2 Material Conditioning
	4 Analytical Modelling
	5 Experimental and Analytical Results
	6 Numerical Simulation of Impact on MATEGLASS
		6.1 Model Set-up
		6.2 Materials Properties
		6.3 Results
	7 Discussion
	8 Conclusions
	References
Fluid-Structure Interaction of Composite Structures
	1 Introduction
	2 Experimental Set-Up for FSI with Impact Loading
	3 Experimental Results of FSI with Impact Loading
	4 Numerical Studies of FSI Under Dynamic Loading
	5 Effect on Mode Shapes With FSI
	6 FSI Study of Structure Containing Fluid
	7 Structural Coupling via FSI
	8 FSI on Moving Composite Structures
	9 Conclusions
	References
Low Velocity Impact of Marine Composites: Experiments and Theory
	1 Introduction
	2 Materials and Experiment
		2.1 Materials
		2.2 Experimental Setup
	3 Background: Residual Strength after Impact
	4 Results and Discussion
		4.1 Non Destructive Damage Investigation
		4.2 Semi-empirical Models: Influence of the Temperature
		4.3 Residual Strength: Air-Backed Tests
		4.4 Residual Strength: Water-Backed Impact Tests
		4.5 Effect of the Clamping Device and Fluid-Material Interaction
		4.6 Impact on Specimen Immersed in the Water
		4.7 Introduction to the Theory
	5 Conclusions
	References
Inferring Impulsive Hydrodynamic Loading During Hull Slamming From Water Velocity Measurements
	1 Introduction
	2 A Jump in the Early 1900 to Gain Some Physical Insight
	3 Experimental Setup at NYU
		3.1 Apparatus
		3.2 Data Acquisition and Analysis
	4 PIV-Based Pressure Reconstruction
		4.1 Pressure Reconstruction Using Navier-Stokes Equations
		4.2 Advancements of the Approach
	5 Validation of PIV-Based Pressure Reconstruction
		5.1 Validation Through Experimental Measurements
		5.2 Validation Through Synthetic Data
	6 Exemplary Applications
		6.1 Asymmetric and Oblique Impact of a Rigid Wedge
		6.2 Impact of a Composite Wedge
	7 Conclusions
	References
Response of Sandwich Structures to Blast Loads
	1 Introduction
	2 Loads Produced by Underwater Explosions
		2.1 Shock Wave
		2.2 The Gas Bubble
		2.3 Reflection of the Shock Wave from the Sea Surface and the Sea Bed
		2.4 Cavitation
	3 Response of Ships to an Underwater Explosion
		3.1 Fluid Structure Interaction of Monolithic Plates
		3.2 Fluid Structure Interaction of Composite and Sandwich Plates
		3.3 Bubble Pulsation, Bubble Migration and Cavitation
	4 Computational Modeling of Ships Deformations
		4.1 Fluid Structure Interaction of Monolithic Plates
		4.2 Fluid Structure Interaction of Composite Plates and Sandwich Panels
	5 Summary of Batra´s Team Work
		5.1 Homogenization of Material Properties
		5.2 Modeling 3-D Deformations
		5.3 Reduced-Order Models (Third-Order Shear and Normal Deformable Theory)
			5.3.1 Effect of Curvature on Deformations of Shells
			5.3.2 Effect of Geometric Nonlinearities on Orthotropic Plate´s Deformations
			5.3.3 Stacking Sequence Optimization for Maximizing the Failure Initiation Load
			5.3.4 Fluid-Structure Interaction
	6 Conclusions
	References
The Extended High Order Sandwich Panel Theory for the Static and Dynamic Analysis of Sandwich Structures
	1 Introduction
	2 Formulation of the Extended High Order Sandwich Panel Theory
	3 Accuracy Study I: A Statically Loaded Simply Supported Sandwich Panel
	4 Accuracy Study II: Wrinkling of a Sandwich Panel
	5 Accuracy Study III: Blast Loading of a Simply Supported Sandwich Panel
	6 Conclusion
	References
Mechanics Based Modeling of Composite and Sandwich Structures in the Naval Environment: Elastic Behavior, Fracture and Damage ...
	1 Introduction
	2 Propagation of Plane Strain Harmonic Waves in Layered Plates
		2.1 Multiscale Structural Model for Layered Structures with Interfacial Imperfections
		2.2 The Influence of Interfacial Imperfections on Wave Propagation and Dispersion
		2.3 Conclusions on Wave Propagation Analysis
	3 Elasticity Solutions for Plates with Imperfect Thermal/Mechanical Contact of the Layers
		3.1 Problem and Model
		3.2 Explicit Expressions for Stresses and Displacements in Layered Plates
		3.3 Conclusions on Elasticity Solutions through the Transverse Matrix Method
	4 Linear Elastic Fracture Mechanics Solutions for Sandwich Beams with Face-Core Delaminations
		4.1 Semi-Analytic Solutions for Energy Release Rate and Mode Mixity Phase Angle
		4.2 Application to a DCB Sandwich Specimen: Influence of Shear
		4.3 Conclusions on Interfacial Fracture Mechanics Solutions for Sandwich Beams With Face/Core Delaminations
	5 Interaction of Multiple Damage Mechanisms in Sandwich Beams Subjected to Time-Dependent Loading
		5.1 Models
		5.2 Results for Quasi-Static and Dynamic Loadings
			5.2.1 Elastic-Brittle System under Quasi-static Loading - Discussion and Conclusions
			5.2.2 Influence of Core-plasticity on the Response under Quasi-static Loading - Discussion and Conclusions
			5.2.3 Dynamic Loading - Discussion and Conclusions
	6 Multiscale Structural Modeling of Delamination Fracture in Layered Beams
		6.1 Multiscale Model
		6.2 Single and Multiple, Mode II Dominant Delamination Fracture of Layered Beams
		6.3 Conclusions on Multiscale Homogenized Modeling of Mode II Dominant Fracture
	References
On Characterizing Multiaxial Polymer Foam Properties in Sandwich Structures
	1 Introduction
	2 Pressure Vessel Experiments
	3 Transversely Isotropic Properties
	4 Triaxial Response
		4.1 Triaxial Compression
		4.2 Triaxial Tension/Compression
		4.3 Triaxial Compression and In-Plane Shear
	5 Tsai-Wu Yield Criterion
	6 Material Model
	7 Concluding Remarks
	References
3D Printing of Syntactic Foams for Marine Applications
	1 Introduction
		1.1 AM Process Chain
		1.2 Syntactic Foams
		1.3 Need for 3D Printing of Syntactic Foams for Marine Applications
	2 Materials and Methods
		2.1 Filament Material
		2.2 Pellet Manufacturing and Filament Extrusion
		2.3 Filament Recycling
		2.4 CAD Modeling and 3D Printing
		2.5 Imaging
		2.6 Tensile Testing
	3 Syntactic Foam Filament Manufacturing
		3.1 Filament Quality
		3.2 Filament Microstructure
		3.3 Tensile Behavior
	4 3D Printing of Syntactic Foam
		4.1 Density
		4.2 Microstructure of 3D Printed Syntactic Foams
		4.3 Tensile Behavior
		4.4 3D Printing of a Component
	5 Conclusions
	6 Future Perspectives
	References
Damage Tolerance Assessment of Naval Sandwich Structures with Face-Core Debonds
	1 Introduction
	2 Fracture Mechanics of Sandwich Face/Core Interfaces
		2.1 Griffith Criterion and Use of LEFM
		2.2 Compliance and J-Integral Methods
		2.3 Crack Surface Displacement Extrapolation (CSDE) Method
		2.4 Fatigue Crack Growth
		2.5 The Cycle Jump Technique for Fatigue Crack Growth Calculation
	3 Experimental Fracture Characterisation Methods for Face/Core Sandwich Interfaces
		3.1 Preliminary Remarks
		3.2 Cracked Sandwich Beam (CSB) Test
		3.3 Double Cantilever Beam (DCB) Test
		3.4 Double Cantilever Beam Loaded with Uneven/Unequal Bending Moments (DCB-UBM)
			3.4.1 Description
			3.4.2 DCB-UBM Specimen Design and Analysis
			3.4.3 Novel DCB-UBM Test Rig
		3.5 Tilted Sandwich Debond (TSD) and Modified TSD Specimens
		3.6 Mixed Mode Bending (MMB) Specimen and Test
		3.7 G-Control
		3.8 Shear-Torsion-Bending (STB) Test for Mixed Mode I-II-III Testing
		3.9 Effects of Shear and Near Tip Deformations on Interface Fracture
		3.10 Low (Arctic) Temperatures
	4 Modelling and Testing of Sandwich Structural Components with Debonds
		4.1 Curved Beams with Debonds
		4.2 Debonded Sandwich Columns in Axial Compression
		4.3 Debonded Sandwich Panels in Axial Compression
		4.4 Debonded Sandwich Panels under Lateral Pressure Loading
		4.5 X-Joints under Fatigue Loading: STT Test Feature
		4.6 Improving Damage Tolerance
	5 Damage Tolerance and Assessment Procedures for Naval Sandwich Vessels
		5.1 Introduction
		5.2 The SaNDI Project: Background and Aims
		5.3 Details of the SaNDI Approach to Damage Assessment Based on Residual Strength
		5.4 Simplified Procedure Developed for On-Board Use
		5.5 Application to Fatigue Loading
		5.6 Direct Estimation of Residual Fatigue Life: Integrated Fatigue Prediction System
	6 Conclusion
	References
Modeling Nonlinear and Time-Dependent Behaviors of Polymeric Sandwich Composites at Various Environmental Conditions
	1 Introduction
	2 Experiments
	3 Constitutive Material Models for the Constituents
		3.1 Nonlinear Viscoelastic Model for Foam
		3.2 Elastic-Plastic Model for Skins
	4 Results and Discussion
		4.1 Uniaxial Tension Response of Skins
		4.2 Bending Tests on Foams
		4.3 Bending Response of Sandwich Composites
		4.4 Time-Dependent Response of Foams and Sandwich Composites
	5 Conclusions
	References
Towards More Representative Accelerated Aging of Marine Composites
	1 Introduction
	2 Acceleration by Increasing Temperature
	3 Acceleration by Applied Mechanical Loads (Stress-Diffusion Coupling)
	4 Acceleration by Increasing Hydrostatic Pressure
	5 Acceleration by Modifying Coupon Geometry
	6 Influence of Aging Medium on Acceleration
	7 Summary of Acceleration Factors
	8 Examples of Long Duration (> 5 Year) Immersion Studies
		8.1 Carbon Fiber Reinforced Composite
		8.2 Glass Fiber Reinforced Composite
	9 Other Factors Required to Improve Representativity of Testing
	10 Conclusions
	References
Statistical Long-Term Creep Failure Time of Unidirectional CFRP
	1 Introduction
	2 Statistical Prediction of Creep Failure Time of CFRP
	3 Molding of CFRP Strands and Testing Methods
	4 Results and Discussion
		4.1 Creep Compliance of Matrix Resin and Static Strength of Carbon Fibers
		4.2 Static Tensile Strengths of CFRP Strands at Various Temperatures
		4.3 Static Tensile Strength of CFRP Strand Against Viscoelastic Compliance of Matrix Resin
		4.4 Master Curves of Static Tensile Strength for Various CFRP Strands
		4.5 Experimental and Predicted Statistical Creep Failure Times for Various CFRP Strands
		4.6 Fractographs Obtained After Static and Creep Tests
	5 Conclusion
	References
Effect of Seawater on Carbon Fiber Composite Facings and Sandwich Structures With Polymeric Foam Core
	1 Introduction
	2 Materials
	3 Materials Preconditioning to Simulate Marine Environment
	4 Seawater and Temperature Effects on Constituent Materials
	5 Effect of Seawater and Microstructure on Composite Laminates (Facings)
	6 Fatigue Behavior of Sandwich Facing Material and Seawater Effect
	7 CFVE Sandwich Structure Fatigue Behavior Exposed to Sea Water
	8 Compressive Behavior and Seawater Effects
	9 Summary
	References
Failure Mechanics of Low Velocity Dynamic Impact on Woven Polymeric Composites in Arctic Conditions
	1 Introduction
	2 Experimental Procedures
		2.1 Manufacturing
			2.1.1 Material System
			2.1.2 Laminate Fabrication
		2.2 Impact Tests
		2.3 Quasi-Static Tests
		2.4 Micro Computed Tomography (micro-CT) Scanning
	3 Results and Discussion
		3.1 Laminate Strengthening
			3.1.1 Compression Test Results
			3.1.2 Tension Test Results
		3.2 Contact Force and Deflection
			3.2.1 Single Impact
			3.2.2 Repeated Impact
			3.2.3 Temperature Effect on Impact Force
			3.2.4 Temperature Effect on Deflection
		3.3 Absorbed Energy
			3.3.1 Single Impact
			3.3.2 Repeated Impact
			3.3.3 Temperature Effect on the Degree of Damage Under Repeated Impact
		3.4 Damage Mechanisms
			3.4.1 Single Impact
			3.4.2 Repeated Impact
	4 Conclusion
	References
Behavior of Composite Materials and Structures in Low Temperature Arctic Conditions
	1 Introduction
		1.1 Background and Motivation
		1.2 Influence of Low Temperature on Composite Laminates
	2 Experimental Details
		2.1 Specimen Preparation
		2.2 Impact Testing Setup
		2.3 X-ray Micro-computed Tomography Analysis of Internal Damages
		2.4 Compression After Impact Test Setup
		2.5 Flexural After Impact Test Setup
	3 Results and Discussion
		3.1 Impact Damage Response
		3.2 Impact Damage Critical Forces
		3.3 Impact Damage Absorbed Energy
		3.4 Impact Damage Mechanisms
		3.5 CAI Performance
		3.6 Flexural After Impact Performance
	4 Conclusion
	References
Mapping Interior Strain Fields in Thick Composites and Sandwich Plates With Digital Volumetric Speckle Photography Technique
	1 Introduction
	2 Theory of Digital Volumetric Speckle Photography (DVSP)
	3 Strain Estimation
	4 Experiments & Results
		4.1 Experimental Setup
		4.2 A Woven Composite Beam Under 3-Point Bending
		4.3 A Woven Composite Beam With a Prepared Slot Under 3-Point Bending
		4.4 A Woven Sandwich Beam Under 3-Point Bending
	5 Discussion
		5.1 The Effect of Subset Size
		5.2 Influence of Artifacts in CT Images
	6 Conclusion
	References
Index