AERO 401 Guest Materials (2)

8/2/2019 AERO 401 Guest Materials (2)

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Material Selection forAerospace Applications

Darren Pyfer, P.E.Engineering Specialist Senior

October 16, 2001


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Agenda

Vought Aircraft Industries Corporate Overview

Material Selection Criteria

Material Types

Material Forms

Examples


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Vought Aircraft Industries

Corporate Overview


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Vought Company Overview

Largest Single Supplier of Aerostructures to Boeing:

- Producing More of the747 Structure Than AnyOther Commercial

Supplier for Boeing

- Producing More of the

C-17 Structure Than AnyOther Military Supplierfor Boeing


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Vought Company Overview (cont.)

Largest Single Supplier of Aerostructures toGulfstream Aerospace

Designed and BuildIntegrated Wing System

for the Gulfstream GVAs a Risk-sharing TeamMember


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Vought Company Overview (cont.)

Largest Single Supplier of Aerostructures toNorthrop on the B-2 Stealth Bomber Program

Designed and Built theIntermediate Wing

Section of the B-2Bomber including theEngine and LandingGear Bays


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Vought Commercial Products

777

GIV HAWKER 800

CF34

CFM56

CF6

GV

767737747

757


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Vought Military Products

S-3 F-14 E-2C P-3

V-22

EA-6B

Global Hawk

T-38

C-17 F/A-18E/F E-8C/JSTARS


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Vought Product Line Summary

C-17

Empennage Fuselage Doors WingsNacelleComp

ControlSurfaces

GV

737

747

757

767

777


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Material Selection Criteria


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Static Strength

Material Must Support Ultimate Loads WithoutFailure. Material Must Support Limit Loads WithoutPermanent Deformation.

Initial Evaluation for Each Component

Usually Aluminum Is the Initial Material Selection

If Aluminum Cannot Support the Applied LoadWithin the Size Limitation of the Component,Higher Strength Materials Must Be Considered(Titanium or Steel)

If Aluminum Is Too Heavy to Meet thePerformance Requirements, Graphite/Epoxy orNext Generation Materials Should BeConsidered


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Stiffness

Deformation of Material at Limit Loads Must NotInterfere With Safe Operation

There Are Cases Where Meeting the StaticStrength Requirement Results in a ComponentThat Has Unacceptable Deflections

If That Is the Case, The Component Is Said to Be aStiffness Design


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Fatigue (Crack Initiation)

The Ability of a Material to Resist Cracking UnderCyclical Loading

Spectrum Dependant

Stress Concentration Factors

Component Is Limited to a Certain Stress Level

Based on the Required Life of the Airframe Further Processing May Improve Fatigue

Properties Such As Shot Peening or Cold Working


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Damage Tolerance (Crack Growth)

The Ability of a Material to Resist Crack PropagationUnder Cyclical Loading

Slow Crack Growth Design

Use of Alloys With Increased Fracture Toughness


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Weight

Low Weight Is Critical to Meeting AircraftPerformance Goals

Materials Are Tailored for Specific Requirementsto Minimize Weight

Materials With Higher Strength to Weight Ratios

Typically Have Higher Acquisition Costs but LowerLife Cycle Costs (i.e. Lower Fuel Consumption)


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Corrosion

Surface Corrosion

Galvanic Corrosion of Dissimilar Metals (seeChart)

Surface Treatments

Proper Drainage

Stress Corrosion Cracking

Certain Alloys Are More Susceptible to StressCorrosion Cracking (see Chart)

Especially Severe in the Short Transverse GrainDirection


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Dissimilar Metal Chart


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Stress Corrosion Cracking (SCC) Chart


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Producibility

Commercial Availability

Lead Times

Fabrication Alternatives

Built Up

Machined From Plate Machined From Forging

Casting


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Cost

Raw Material Cost Comparisons

Aluminum Plate = $2 - $3 / lb.

Steel Plate = $5 - $10 / lb.

Titanium Plate = $15 - $25 / lb.

Fiberglass/Epoxy Prepreg = $15 - $25 / lb.

Graphite/Epoxy Prepreg = $50 - $100 / lb.

Detail Fabrication Costs

Assembly Costs

Life Cycle Costs

Cost of Weight (Loss of Payload, Increased FuelConsumption)

Cost of Maintenance


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Specialized Requirements

Temperature

Lightning and Static Electricity Dissipation

Erosion and Abrasion

Marine Environment

Impact Resistance

Fire Zones

Electrical Transparency


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Performance vs. Cost Dilemma

Highest Performance For The Lowest Cost Is theGoal of Every Airplane Material Selection.

Mutually Exclusive

Compromise Is Required

Define the Cost of Weight to the Aircraft


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Material Types


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Aluminum

Aluminum Accounts for ~80% of the StructuralMaterial of Most Commercial and Military TransportAircraft

Inexpensive and Easy to Form and Machine

Alloys Are Tailored to Specific Needs 2000 Series Alloys (Aluminum-copper-magnesium)

Are Medium to High Strength With Good FatigueResistance but Low Stress Corrosion CrackingResistance.

2024-T3 Is the Yardstick for Fatigue Properties

5000 and 6000 Series Alloys Are Low to MediumStrength but Easily Welded


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Aluminum (cont.)

7000 Series Alloys (Aluminum-zinc-magnesium-copper) Are High Strength With Improved StressCorrosion Cracking Resistance but Most Have NoBetter Fatigue Properties Than 2000 Series

7050 and 7075 Alloys Are Widely Used

7475 Alloy Provides Higher Fatigue ResistanceSimilar to 2024-T3


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Aluminum Tempers


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Aluminum Tempers (cont.)


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Aluminum Tempers (cont.)


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Aluminum Comparison Chart

Material Typical Application

2024-T3,T351,T42

High Strength Tension Applications. BestFracture Toughness/Slow Crack Growth Rateand Good Fatigue life. Thick Forms Have LowShort Transverse Properties including StressCorrosion Cracking.

2324-T3 8% Improvement In Strength Over 2024-T3 WithIncreased Fatigue And Toughness Properties.

7075-T6,T651,T7351

High Strength Compression Applications.Higher Strength Than 2024-T3, But LowerFracture Toughness. T7351 has Excellent

Stress Corrosion Cracking Resistance andBetter Fracture Toughness Than T6.

7050-T7451 Better Properties Than 7075-T7351 In ThickerSections.


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Titanium

Better Strength To Weight Ratio Than Aluminum or

Steel

Typically Comprises ~5% By Weight in CommercialAircraft and Up To ~25% By Weight For HighPerformance Military Aircraft

Good Corrosion Resistance

Good Temperature Resistance

Good Fatigue And Damage Tolerance Properties In

The Annealed Form Typical Alloy Is Ti 6Al-4V Either Annealed or Solution

Treated and Aged

High Cost For Metals


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Steel

Steel May Be Selected When Tensile StrengthsGreater Than Titanium Are Necessary

Steel Is Usually Limited to a Few Highly LoadedComponents Such As Landing Gear

There Are Many Steel Alloys to Choose From (SeeChart); Select the One That Is Tailored for YourApplication.


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Steel (cont.)

Mil-Hdbk-5 List of Aerospace Steel Alloys:


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Composite

The Embedding of Small Diameter High Strength HighModulus Fibers in a Homogeneous Matrix Material

Material Is Orthotropic (Much Stronger in the FiberOriented Directions)

Fibers Graphite (High Strength, Stiffness)

Fiberglass (Fair Strength, Low Cost, SecondaryStructure)

Kevlar (Damage Tolerant)

Matrix

Epoxy (Primary Matrix Material) to 250 F

Bismaleimide (High Temp Applications) to 350 F


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Material Properties Comparison

Material Ftu

ksi

Fty

(ksi)

Fcy

(ksi)

E

106

si

Density

(lb/in3

)2024-T3 Aluminum 64 47 39 10.5 .1017075-T6 Aluminum 78 71 70 10.3 .1016Al-4V TitaniumAnnealed

134 126 132 16.0 .160

6Al-4V TitaniumSolution Treated andAged

150 140 145 16.0 .160

15-5PH StainlessSteel (H1025)

154 145 152 28.5 .283

Fiberglass Epoxy(Unidirectional)

80 60 5 .065

Graphite Epoxy(Unidirectional)

170 140 22 .056


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Next Generation Materials

Aluminum Lithium

GLARE (Fiberglass Reinforced Aluminum)

TiGr (Graphite Reinforced Titanium)

Thermoplastics

Resin Transfer Molding (RTM)

Stitched Resin Fusion Injected (Stitched RFI)


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Mil-Hnbk-5 Overview

Document Contains Design Information On The

Strength Properties of Metallic Materials andElements for Aerospace Vehicle Structures. AllInformation and Data Contained in This HandbookHave Been Coordinated With the Air Force, Army,Navy, Federal Aviation Administration and IndustryPrior to Publication and Are Being Maintained As aJoint Effort of the Department of Defense and theFederal Aviation Administration.


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Basis of Properties

Material Property Selection Is Dependant on the

Criticality of the Structural Component Critical Single Load Path Structure

A Basis (99% Probability of Exceeding)

S Basis (Agency Assured Minimum Value)

Other Primary Structure With Redundant LoadPaths

B Basis (90% Probability of Exceeding)

Without a Test, A or S Basis May Be Required

Secondary Structure B Basis (90% Probability of Exceeding)


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Grain Direction


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Material Properties (Mil-Hdbk-5) Example

Type


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Material Forms


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Sheet

Rolled Flat Metal Thickness Less Than .25

Fuselage Skin

Fuselage Frames

Rib and Spar Webs

Control Surfaces

Pressure Domes

Good Grain Orientation

Many Parts and Fasteners

Fit Problems Straighten Operations

Shims

Warpage


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Plate

Rolled Flat Metal Thickness Greater Than .25

Wing and Tail Skins

Monolithic Spars and Ribs

Fittings

Unitized Structure; Fewer Fasteners Grain Orientation Can Be a Problem

High Speed Machining Has Lowered Fab Costs


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Extrusion

Produced By Forcing Metal Through a Forming Die At

Elevated Temperature To Achieve The Desired Shape Stringers

Rib and Spar Caps

Stiffeners

Grain Is Aligned in The Lengthwise Direction

Additional Forming and Machining Required

Used In Conjunction With Sheet Metal Webs


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Forging

Produced by Impacting or Pressing The Material Into

The Desired Shape Large Fittings

Large Frames/Ribs

Odd Shapes

Control GrainOrientation

Residual StressesCan Cause

Warpage Tooling Can Be

Difficult


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Casting

Produced By Pouring Molten Metal Into A Die To

Achieve The Desired Shape Nacelle/Engine Components

Complex Geometry

Dramatically Lowers Part and Fastener Counts

Poor Fatigue And Damage Tolerance Properties

High Tooling Costs


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Composite

Produced By Laying Fabric, Laying Tape, Winding,

Tow Placement and 3D Weaving or Stitching Skins

Trailing Edge Surfaces

Interiors and Floors

Properties Can beOriented To Load Direction

Excellent Strength ToWeight Ratio

High Cost Of Material andProcesses

Poor Bearing Strength


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Examples


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Upper Wing Cover

Skin - 7075-T651 Aluminum

Plate

Stringers - 7075-T6511Aluminum Extrusion

After Machining; Age CreepFormed To -T7351/-T73511

Compression Dominated

Reduces Compressive Yield

Strength Greatly Increases Stress

Corrosion Resistance


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Lower Wing Cover

Skin - 2024-T351 Aluminum

Plate

Tension Dominated

Good Ultimate TensileStrength

Very Good Fatigue andDamage Tolerance Properties

Stringers - 7075-T73511

Aluminum Extrusion High Ultimate Tensile Strength

Good Damage ToleranceProperties


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Spars

7050-T7451 Aluminum Plate

High Tensile andCompressive Strength inThick Sections

Good Stress CorrosionResistance


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Fixed Trailing Edge Surface

Graphite/Epoxy Fabric

Aramid/PhenolicHoneycomb

Fiberglass/Epoxy FabricCorrosion Barrier

Secondary Structure

Stiffness Design


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Leading Edge

2024-0 Clad Aluminum

Heat Treated to -T62 After Stretch Forming to Shape

Clad For Corrosion Resistance

Polished For Appearance

De-icing by Hot Air/Bird Strike Resistance


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Landing Gear Support Beam

Titanium 6Al-4V Annealed

Forging

High Strength and Stiffness

Critical Lug Design

Height is Limited By WingContours

Annealed FormIs Good ForFatigue AndDamageTolerance


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Wing to Body Attachments

PH13-8Mo Cres Steel Bar

Critical Lug Design

High StrengthRequirement

Good CorrosionResistance


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Flap Tracks

PH13-8Mo Cres Steel Bar

Geometry Is Very LimitedBy Requirement To BeInternal To The Wing

Results In Very HighStress Levels

High Stiffness Is RequiredTo Meet Flutter and FlapGeometry Criteria

Good CorrosionResistance

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