Cirrus LSA Wing Design Team Lead: David Gustafson Tyler Hawkins Nick Brown Bryce Holmgren.
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Transcript of Cirrus LSA Wing Design Team Lead: David Gustafson Tyler Hawkins Nick Brown Bryce Holmgren.
Cirrus LSA Wing Design
Team Lead: David GustafsonTyler Hawkins
Nick BrownBryce Holmgren
Project Goals
• Utilize Edge Bonding
• Try New Light Weight Materials
• Incorporate Spin Resistance
• Total Weight Constraint
–< 170 lbs for entire wing
Obstacles
• Edge Bonding vs. Required Strength and Existing Practice
• New Materials– Cost
– Performance
• Spin Resistance vs. Manufacturing Simplicity
• All of These vs. Weight and Performance
Areas of Design and Analysis
• Loads Analysis
• Aerodynamic Design
• Materials Research and Testing
• Structural Design
Cirrus Wing
Aerodynamics and ControlBryce Holmgren
AerodynamicsDesign Constraints
Light Sport Aircraft Requirements• Maximum Gross Weight: 1,320lbs• Maximum Stall Speed: 45 knots• Required Lift Coefficient to Meet Requirements:
>1.60
Other Considerations• Spin Resistant Design• Enhanced Stall Performance
Aerodynamics
Analysis Tools – XFLR5• Developed by MIT• Contains Airfoil Generation Tool Called Xfoil• Recommended by Cirrus for Preliminary
Design Analysis
Aerodynamics
Initial Wing Design Parameters • Wing Span: 30 ft• Wing Area: 125 square ft
Airfoil Database – University of Illinois at Urbana-Champaign
Aerodynamics
Final Airfoil - NASA/Langley LS(1)-0417mod (also known as the GA(W)-1 airfoil)
Aerodynamics
Drooped Leading Edge• Enhanced Spin Resistance
AerodynamicsDrooped Leading Edge vs Standard Airfoil
AerodynamicsWing Model in XFLR
Plane weight of 1500 lbs and at 44 knotsLift Coefficient of 1.64 at 17˚ angle of attack
AerodynamicsDesign Summary
Parameter Dimension
Wing Area 123.07 ft^2
Wing Span 30 ft
Root Chord 4.5 ft
Tip Chord 3.7 ft
Mean Aerodynamic Chord 4.11 ft
Wing Loading 12.2 lbs/ft^2
Aspect Ratio 7.3
Taper Ratio 1.2
Dihedral Angle 5 Degrees
Max Lift Coefficient 1.86 @ 19 Degrees Angle of Attack
Aerodynamics
Improvements• Less Aggressive Camber• Different Tip Airfoil
Controls
Flaps• Fowler Flaps • Area: 24.4 ft^2
Ailerons• Differential Ailerons• Area: 12 ft^2
Cirrus Wing
MaterialsNick Brown
LSA FAA definition
• Max gross takeoff weight = 1320 lbs
• Max stall speed = 45 knots
• Maximum speed in level flight = 120 knots
ASTM F 2245-07 guidelines
• Limit load factors
• Ultimate load factor of safety = 1.5
• Special ultimate S.F.s for hinges, bearings, pins, control components
• Flight conditions
• Design speeds
Design speeds
• 45 knots = Stall speed (LSA)
• 99.6 knots= Minimum maneuvering Speed
• 108 knots = Minimum cruise
• 120 knots = Maximum cruise (LSA)
• 160 knots = Dive speed
Flight envelope
Flight Envelope
12099.6 159.27
45
-3
-2
-1
0
1
2
3
4
5
0 50 100 150 200
Speed (in knots)
Lo
ad F
acto
r n
Vs
VA VC,max VD
Total Loads
• Level flight 1320 lbs
• Design Limit load = 5280 lbs
• Ultimate load = 7920 lbs (for 3 seconds)
XFLR5
• Simulations– Various A.O.A. and Reynolds numbers
–Wing panels
• Data (spreadsheet)– Aerodynamic coefficients
– Lift, drag, and moment forces
XFLR5
XFLR5
XFLR5
DistributionS ec tional L ift D is tribution
y = -0.6938x 2 + 11.615x + 9.1203
y = -3.255x 2 + 54.497x + 42.791
0
50
100
150
200
250
300
350
0 2 4 6 8 10 12 14 16spa n position (ft)
L' (
lbs/
ft)
real load
real load(drooped L E )
ultimate load
ultimae load (droopedL E )
Shear and bending
• Integrate ultimate load equations– From 0(root) to 8ft (airfoil switch)• F = -5.2139x + 318.37
– From 8ft to tip (15ft)• F = -3.255x2 +54.497x + 42.791
Torsion/control loads
• 75% positive maneuvering load, plus torsion from max aileron displacement
• Gust loads at VF with flaps extended (7.5 m/s)
Gusts
• Symmetric vertical gusts (up and down)– 15 m/s at VC
– 7.5 m/s at VD
Cirrus Wing
Composite Panels & Adhesives
David Gustafson
Composite Panels
• Panels are fiberglass on both sides with a core in the middle consisting of either foam or a honeycomb structure
Fiberglass Core: Foam or Aramid
Core Options
Material DensityCompresive
StrengthTensile
strengthShear
SengthShear
ModulusCost
units (lb/ft^3) psi psi psi psi ($/ft^3)
Cirrus - HT 61 4.1 145 261 131 2900 4.96
Evonik 51 A - PMI Foam 3.248 131 276 116 2760 -
Ultracor UCF-83-1/4-3.0 3 246 27 223 61000
Aramid Core .25 In. Thick 1.8 109 - 52/62 (L/W)1579/2882
(L/W)7.95
Aramid Core .125 In. Thick 1.8 109 - 52/62 (L/W)1579/2882
(L/W)4.95
Final Core Material
• HT Diab 61- Wing Skins
• Ability to lay up curves of Airfoils
• Cheapest that met criteria of foams
• Aramid Core- Spar, Aft Spar, Rib
• Light Weight
• Cheapest per Pound
Adhesive Options• DP 420– 3M, Two Part Epoxy
» From 3M Epoxy Comparison
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Adhesive Options (Cont.)
• PTM & W: – ES6292 Lightweight Tough Epoxy Adhesive• Two Part Epoxy
• Designed for use in the structural assemblies involving composites
• Already used by Cirrus Design Center
Adhesive Testing
• Objectives:– Test Max Adhesive Loads• Need to make sure adhesives aren’t effected by surfaces
– Test surface preparation techniques
Adhesive Testing (Cont.)
• Materials Tested:– Adhesives:• PTM & W ES6292
• 3M DP 420
– Composites:• Aramid Core with Fiberglass Skin
• HT Diab Foam Core with Tencate Fiberglass
Adhesive Testing (Cont.)
• Tensile Test:– Load Bonds in Tension–Measure Load at Fracture– Calculate Lbs/In. Bond Strength
• Test Equipment:– Constant Strain Load Cell–Measures Load and displacement
Adhesive Testing (Cont.)
Adhesive Testing (Cont.)
• Tensile Load Justification:– Jaws:• 2° freedom on both directions
– Top & Bottom
• All samples were applied within 1 degree of perpendicular
• Therefore: Tension loads were perpendicular to bond
Adhesive Testing (Cont.)
• Surface Preparation:– All surfaces were lightly sanded to rough up
surface
– All surfaces were cleaned with to remove
Adhesive Testing (Cont.)
• Results:– Bond Strength per Inch of Bond (Lbs/In)
• PTM & W ES6292= 81.7 ± 4.1 Lbs/In
• 3M DP 420=87.1 ± 4.4 Lbs/In
» Uncertainty Estimated at 5%
Adhesive Testing (Cont.)
• Conclusions:– Adhesives were comparable in
Strength per Inch
– Both Adhesives meet strength requirements for wing
– PTM & W ES6292 Adhesive is better because of lower cost
Adhesive Testing (Cont.)
• Errors:– Improper preparation:• Issue: Samples broke at surface
• Resolution: Better Surface Preparation– Sanding (possibly Sand Blasting)
– Better Removal of oils from surface
• Effect:– Bonds Broke Prematurely– With Better Preparation Bonds could hold more Weight
Adhesive Testing (Cont.)
– Test Equipment:• Issue: Jaws Slipping• Resolution: Better Transition from Material to Jaw
– Adhere Aluminum Tab into Composite– External Clamp System with Aluminum Tab for Jaw
» Allow Material to be secured by clamp and Jaw to attach to Aluminum Tab
• Effect:– Load might be underestimated. – Result: Bond Strength could be higher than reported
Adhesive Testing (Cont.)
• Further Testing:– Shear Test Side View:
Composite A
Composite B
Adhesive Testing (Cont.)
– Shear Test Top View:(Load Pulling out from picture)
Composite A
Composite B
Bond
Adhesive Testing (Cont.)
• Shear Test:
Cirrus Wing
StructuresTyler Hawkins
Structure
• Goals– Light Weight• < 170 lbs. in total
–Handle All Loads with Extra Safety Factor–Maintain Aerodynamic Shape–Attach to Fuselage Structure
Component Break Down
• Wing Skin• Main Spar• Aft Spar• Ribs• Leading Edge Braces
Wing Skin
• NEEDS–Light Weight–Easily formed into complex
surfaces–Durable –Puncture and Tear Resistant
Solutions
• Use 2-Core-2 construction for the wing• Fiberglass–45o angles
• Core–.25 inch–Density = .00145 lb/in3
Wing Skin Lay Up
Reasoning
• Process is known and used at Cirrus• Creates a Very puncture resistant material• Fiberglass performs well in multiple directions– ±45 degree orientation
• Light Weight material• Possible Improvements– Cut away sections of Foam where not needed– Use Honeycomb Aramid Core to cut weight
Main Spar
• NEEDS–Light Weight–Handle Compression, Tension, and
Shear–Provide Bond Surface for Ribs and Skin–Serve as Attachment to Fuselage
Spar Designs Considered
• C-Channel– Provides Good Bonding Surface– Would be made Entirely of Carbon– Similar to Existing Cirrus Designs
• Why Not– Looking for Two Piece Main Spar Assembly– Incorporating Aramid Core Can Lighten Structure
Rectangle Spars
• 4 – Core – 4– Simple Design– 1 Piece Core– One Width Carbon Cap
• Why not?– Too thick adds core weight– Too thin makes carbon lay up with many thin
strips
Examples of Rectangle Spars
I-Beam Spar
• Provides Similar Shear, Tension, Compression coverage to Rectangle
• Thinner Shear Web • Very Light Weight• Provides Large Bonding Surface to Wing Skin• Potential Drawbacks– Upfront Tooling– Layup Complexity
Caps
• Carbon– Laid Up as T-shape–Carbon Strips– Tensile Strength: 2.62*105 Psi–Compressive Strength: 1.42*105 Psi–Absorbs Forces on Top and Bottom of Spar
at Low Weight Cost
Spar Web
• Core– .3 inch Aramid Core• Very Light Weight• Bonds Well To Cirrus’s Fiberglass
– 4 ply fiberglass quilt on both Sides of Core• Provides the Shear support• Alternate Ply orientations (±45 degrees)• Performs very well in Shear (23800 Psi Shear strength)• Low Cost and Ease of Use
General Lay Up Scheme
*All units in Inches
Specific Modifications
• Taper Layers Until 4 Layers Left• Run 4 Layers to End Plus Alpha Section– Allows for Wide Bond Area– Need to only cut two strip Widths (α and cap)
• Taper These Quickly at the end of the Spar to Avoid Large Stress Concentration
Connection To Fuselage
• Fuselage Width: 48 in.• Extend Both Spars Through Fuselage• Attachments– 2 Hard Points for Bolts Between Spars– Bracket for Spars to Transfer Load to Fuselage– 1 Hard Point each Rear Spar 6 Inches into Fuselage
Attachment Point
Hard Points
• Options– Fiberglass Laid In Through Entire Spar– Aluminum Plug Laid Into Spar– Aluminum Plug Glued Into Spar
• Chose Aluminum Plug Laid Into Spar– 6061-T6• Light Weight• High Bearing Strength
Hard Point Dimensions
• Use .75 inch bolt/plug to attach structure• 0.3 inches thick• 3.75 inches in diameter• Spacing of 46 inches on center, 23 on either
side of WS0.
Aft Spar
• Simple Design• 2-Core-2• Aramid Core• 2 layers of Glass on Each Side• No Caps-Only Shear Felt Here
Ribs and Leading Edge Supports
• 2-Core-2 Construction• Aramid Core• Can Make Sheets of This and Water Jet Cut
Specific Panels– Also Aft Spar
• Provide Bond Length to Hold Skin and Structure Together
Rib Spacing
Airplane Design by Jan Roskam suggest 36” spacing for Light aircraft.
Rib to Skin Bonding
3-D view of Interior Structure
Structure with Skin Attached
Weight Estimate
Cirrus Wing
Build/TestNick Brown
Cirrus Wing
Manufacturing and AssemblyBryce Holmgren
ManufacturingPart Fabrication
Spars made using semi-automated system
ManufacturingPart Fabrication
Ribs and shear web water jet cut from single sheet of Nomex/glass composite
• Ventilation required when machining produces dust, mist or vapor
• Light Hand Cotton gloves for General Protection
ManufacturingPart Fabrication
Wing skins assembled in custom tooled forms
ManufacturingFinal Wing Assembly
ManufacturingFinal Assembly
ManufacturingEpoxy Health Concerns
Effects of Overexposure:– Eyes: Causes severe conjunctive irritation, Corneal injury
and Iritis– Skin: May cause irritation, burns, ulceration, or skin
sensitization– Inhalation: Vapors are irritating and cause tears, burning of
nose and throat, coughing, wheezing nausea and vomiting– Ingestion: Moderately toxic, may cause mouth and throat
burns, abdominal pain, weakness, thirst and coma.– Chronic: Amine vapors may cause liver and kidney injury.
Eye, skin or lung may develop or be irritated by Amine vapors.
[From MSDS of ES6292B with Beads]
ManufacturingSafety Precautions
• Respiratory: Not required unless process is creating dust, mist or vapor.
• Ventilation: Breathing of vapor must be avoided.• Hand Protection: Impervious gloves, neoprene or
rubber, must be worn• Eye Protection: Splash proof Goggles or safety
glasses• Other: Clean body covering clothing and shoes
[From MSDS of ES6292B with Beads]
Business Case
David Gustafson
Project Goals
• Design a Composite Wing– Comoposite Panels– Edge Bonding Technique
• Meet Design Criteria:– 170 Lbs or less– No Spin Criteria in Airfoil
Financial Summary
• Upfront Costs:– Wing Lay up Structure– Final Assembley– Safety Equipment
• Gloves• Goggles• Respirators
– Water Jet Cutting Equipment• Alternate Option:
– Contract for pieces to be Water Jet Cut
Financial Summary
• Material Cost of Wing:– Carbon: $123– Aramid Core: ~$840– Foam: ~$300– Fiberglass: ~$400– Adhesive: ~$100
Total: ~$1700
Justification
• Structure Meets Design Loads– Bonds Safety Factor >5
• Manufacturing Process – Streamlined– Cost Effective
• No Spin– Drooped Leading edge in Airfoil
Justification
• Edge Bonding– Allowed for a low weight design– Less Complex Manufacturing System– Meets strength Criteria
Thank You For Your Time and Consideration