Emerging Research Alliances between US Academia and Industry

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1 Emerging Research Alliances between US Academia and Industry Mark E. Tuttle, Professor and Chair, Dept Mechanical Eng Director, AMTAS University of Washington, Seattle, WA, USA

2 Where are Seattle and the University of Washington located?! Seattle

3 Seattle and the Aerospace Industry Bill Boeing founded his company in Seattle in 1916 Aeronautical research began at the University of Washington in 1917, when Boeing funded construction of a wind tunnel on the UW campus The Boeing Wind Tunnel at the UW (c. 1918)

4 FAA Centers of Excellence The Federal Aviation Administration Centers of Excellence (COEs) are: Funded through cooperative agreements between academic institutions, their affiliate industrial partners, and the FAA. Funded in three phases over a total period of 10 years (expected to be self-supporting thereafter). Seven FAA-COEs currently exist (for details see

5 The FAA Joint Advanced Materials and Structures (JAMS) COE (2004): The Joint Advanced Materials and Structures (JAMS) Center of Excellence is co-led by the University of Washington (UW) and Wichita State University (WiSU) UW: Center for Advanced Materials in Transport Aircraft Structures (AMTAS) WiSU: Center of Excellence for Composites and Advanced Materials (CECAM) Activities carried out by UW-AMTAS and WiSU-CECAM are coordinated by Mr. Curt Davies of the FAA Hughes Research Center Total JAMS funding to date ~$13M FAA: $6.5M About 30 different industrial partners: $6.5M

6 Where are the University of Washington, Wichita State University, and the Hughes Research Center located?! Seattle, WA Wichita, KS Atlantic City, NJ

7 JAMS-AMTAS-CECAM Mission Perform research studies Provide educational/training opportunities Facilitate knowledge transfer pertinent to the use of advanced materials in transport aircraft

8 CECAM Academic Partners Wichita State University, lead (WiSU) Northwestern University (NWU) Purdue University (PU) Tuskegee University (TU) Univ California at Los Angeles (UCLA) University of Delaware (UD)

9 Where are CECAM Academic Partners located?! Northwestern U. Wichita St. U. Purdue U. U. Of Delaware UCLA Tuskegee U.

10 AMTAS Academic Partners University of Washington, lead (UW) Washington State University (WaSU) Oregon State University (OSU) Edmonds Community College (EdCC)

11 Where are AMTAS Academic Edmonds CC Partners located?! U. Of Washington Washington St. U. Oregon St. U.

12 AMTAS Industry Partners

13 Current AMTAS Projects Reliability-based Damage Tolerant Composite Design Methodologies (Lin, UW) Aeroservoelastic effects in Composite Aircraft (Livne, UW) Adhesive Bonding: Surface Characterization (Flinn, UW) Adhesive Bonding: Effects of Surface Pretreatments (Smith, WaSU) Short Course Curriculum Development: Maintenance of Composite Aircraft Structures (Seaton, EdCC) Modeling Progressive Damage in Composite Aircraft Structures (Kennedy, OSU; to begin Spring 07)

14 Current AMTAS Projects Reliability-based Damage Tolerant Composite Design Methodologies (Lin, UW) Aeroservoelastic effects in Composite Aircraft (Livne, UW) Adhesive Bonding: Surface Characterization (Flinn, UW) Adhesive Bonding: Effects of Surface Pretreatments (Smith, WaSU) Short Course Curriculum Development: Maintenance of Composite Aircraft Structures (Seaton, EdCC) Modeling Progressive Damage in Composite Aircraft Structures (Kennedy, OSU; to begin Spring 07)

15 Reliability-based Damage Tolerant Composite Design Methodologies Phase I Research Tasks Develop a Probabilistic Method to Determine Inspection Intervals for Composite Aircraft Structures: Develop computing tools and algorithms for the probabilistic analysis Establish in-service damage database for existing fleet from FAA SDR and other sources Demonstrate the developed method on an existing structural component

16 Typical In-service Damage Hail Damage

17 Typical In-service Damage- Lightning Strike Engine Cowl

18 Identification of Critical Parameters Various Failure Modes Strength vs. Temperature Moisture Content vs. Time R W,% T Strength Degradation due to Aging Effects R Life time Residual Strength vs. Damage Size & Damage Type R Time Probability of Detection vs. Damage Size & Damage Type 2L Probability of Failure Maximum Load vs. Time of Damage Existence Damage Size Damage Size & Damage Type Spectra Structural Temperature Spectra Maximum Load Damage Size Temperature Inspection Intervals, Repair Repair Criteria, Structural Risk Risk

19 Current AMTAS Projects Reliability-based Damage Tolerant Composite Design Methodologies (Lin, UW) Aeroservoelastic effects in Composite Aircraft (Livne, UW) Adhesive Bonding: Surface Characterization (Flinn, UW) Adhesive Bonding: Effects of Surface Pretreatments (Smith, WaSU) Short Course Curriculum Development: Maintenance of Composite Aircraft Structures (Seaton, EdCC) Modeling Progressive Damage in Composite Aircraft Structures (Kennedy, OSU; to begin Spring 07)

20 Aeroservoelastic Effects in Composite Aircraft Motivation and Key Issues Local structural variations in composite airframes (damage and repair, material changes over time, hinge stiffness and freeplay, etc) affects global aeroelastic and aeroservoelastic stability and response. Objectives Develop computational tools (validated by experiments) for local/global nonlinear analysis of integrated structure-aerodynamiccontrol systems subject to multiple local structural variations. Develop a better understanding of effects of local structural and material variations in composites on overall aeroservoelastic integrity. Establish a collaborative expertise base for FAA, NTSB, and industry needs related to future need for aeroservoelastic analyses

21 The Benchmark 2DOF Airfoil / Flap System Freeplay ± δ Fig.Ref. Dowell&Tang Nonlinear Spring

22 Vertical Tail / Rudder FEM 767-size vertical tail / rudder structure Fixed at root Rudder actuated at 5 pivot points along hinge line All composite structure: Graphite/Epoxy and E-Glass/Epoxy 11 Property cards: 2 skin cards; 4 web cards; 2 caps cards; 2 vertical stiffener cards 1 actuator card 232 Nodes 1851 Elements: 1308 Membranes; 503 Bars; 35 Rigid Links; 5 Rotary Actuators

23 Effect of Local Material Property Change on Aeroelastic Poles (Poles at a given flight condition determine stability of motion) Real Part of Pole Imaginary Part of Pole REAL, λ ASE (E + ΔE) IMAG, λ ASE (E + ΔE) pole = 1, comp = open-loop ΔE x λ = λ + jλ R t e λ ΔE x I Change in elastic modulus (E) of composite skin panels at root (all layers [0/90/+45/-45] s ; both sides)

24 Effect of Local Structural Change on Aeroelastic Poles λ = λ + jλ R I t e λ Change in rudder mass (e.g., moisture absorption) REAL, λ ASE (ρ + Δρ) Real Part of Pole Imaginary Part of Pole IMAG, λ ASE (ρ + Δρ) pole = 3, comp = open-loop Δρ Δρ

25 Current AMTAS Projects Reliability-based Damage Tolerant Composite Design Methodologies (Lin, UW) Aeroservoelastic effects in Composite Aircraft (Livne, UW) Adhesive Bonding: Surface Characterization (Flinn, UW) Adhesive Bonding: Effects of Surface Pretreatments (Smith, WaSU) Short Course Curriculum Development: Maintenance of Composite Aircraft Structures (Seaton, EdCC) Modeling Progressive Damage in Composite Aircraft Structures (Kennedy, OSU; to begin Spring 07)

26 Improving Adhesive Bonding of Composites Through Surface Characterization Of Peel Ply Surfaces Motivation and Key Issues Peel ply surface preparation is being used to prepare surfaces for adhesive bonding in commercial transport aircraft structures Good bonds are produced but questions remain: How can suitability of a surface for bonding be determined Does contact angle (wettability) correlate with bonding What is the effect of peel ply texture on surface and bonding What is the effect of moisture in peel ply before cure

27 Improving Adhesive Bonding of Composites Through Surface Characterization Objective Develop further understanding of the effect surface preparation has on the durability of primary structural composite bonds through surface analysis coupled with mechanical testing and fractography

28 Peel Ply Surface Preparation Fracture Possibilities Upon Peel Ply Removal Fracture of the epoxy between peel ply and carbon fibers Fresh, chemically active, epoxy surface is created Interfacial fracture between the peel ply fabric fibers and the epoxy matrix Peel ply fiber fracture Interlaminar failure Fracture Mode controls surface characteristics and bond quality

29 Investigation of Peel Ply Material Type Laminates produced with 3 peel/release plies Polyester BMS (Precision Fabrics 60001) Currently used for primary structural bond prep. Nylon scoured and heat set (Precision Fabrics 52006) Super Release Blue (SBR = PF with siloxane coating) Samples removed for surface characterization SEM, XPS, Contact Angle (wettability), SIMS Laminates bonded and machined into test specimens of various configurations

30 Peel Ply Surface Preparation - SEM Results All samples show acceptable surface on macro scale Interfacial fracture between the peel ply fabric fibers and the epoxy matrix Limited epoxy fracture between peel ply fibers Composite surface after removal of: Nylon Polyester SRB

31 XPS Survey Scan Results Laminate surfaces before bonding, after peel ply removal Laminate Surface Composition Peel Ply %C %O %N %Si Nylon Tr. Polyester SRB Si explains SRB low bond quality.siloxane coating transfers Amount of N on nylon peel ply prepared sample surprising

32 XPS High-Res Results Peel Ply Species BE (ev) % CC/CH Nylon CN Amide (NC=0) CC/CH Polyester CO/(CN) COO Shakeup? (broad) CC/CH SRB CO COO Shakeup? (broad) SRB polyester nylon Amide detected on nylon prepared surface- nylon transfer to surface?

33 Effect of Peel Ply Material Type on Bond Strength Polyester Prepared Nylon Prepared SRB Prepared Adhesive A Failure Mode Cohesive Cohesive & Interlaminar Adhesion G IC (J/m 2 ) Adhesive B Failure Mode Cohesive Adhesion Adhesion G IC (J/m 2 ) G IC and Contact Angle do not always correlate G IC : Polyester >>Nylon> SRB Contact Angle: Nylon < Polyester<< SRB

34 Effects of Peel Ply Texture All polyester peel plies successfully removed Nylon peel plies were more difficult to remove Fine weaves were removed without damage Coarse weaves have not been removed without damage to laminate (3 attempts, different technicians) Material Precision Code Warp (ends/in.) Fill (picks/in.) Polyester Polyester VLP Polyester Polyester Nylon 6, Nylon 6, Nylon 6, Nylon 6, Nylon 6,

35 Current AMTAS Projects Reliability-based Damage Tolerant Composite Design Methodologies (Lin, UW) Aeroservoelastic effects in Composite Aircraft (Livne, UW) Adhesive Bonding: Surface Characterization (Flinn, UW) Adhesive Bonding: Effects of Surface Pretreatments (Smith, WaSU) Short Course Curriculum Development: Maintenance of Composite Aircraft Structures (Seaton, EdCC) Modeling Progressive Damage in Composite Aircraft Structures (Kennedy, OSU; to begin Spring 07)

36 Adhesive Bonding: Effects of Surface Pretreatments Primary Objectives Study effects of adherend moisture content prior to bonding on adhesion, using single lap shear specimens Study effects of peel ply selected for use under wet and dry conditions, based on Creep rupture times measured using single lap shear specimens Strain energy release rates (G Ic ) using Double Cantilevered Beam specimens Crack growth rates measured using modified Wedge Crack Specimens

37 Adhesive Bonding: Effects of Surface Pretreatments Primary Objectives Study effects of adherend moisture content prior to bonding on adhesion, using single lap shear specimens Study effects of peel ply selected for use under wet and dry conditions, based on Creep rupture times measured using single lap shear specimens Strain energy release rates (G Ic ) using Double Cantilevered Beam specimens Crack growth rates measured using modified Wedge Crack Specimens

38 Effects of Peel Ply Based on Creep Rupture Time Creep load levels: 80% of P max SRB = 700 lbs Nylon = 1000 lbs Polyester = 1700 lbs

39 Effects of Peel Ply Based on Creep Rupture Time Mean creep rupture time (hrs) SRB Nylon Polyester Creep rupture duration correlated with initial bond strength Large variation typical of creep rupture Moisture accentuated substrate failure

40 Current AMTAS Projects Reliability-based Damage Tolerant Composite Design Methodologies (Lin, UW) Aeroservoelastic effects in Composite Aircraft (Livne, UW) Adhesive Bonding: Surface Characterization (Flinn, UW) Adhesive Bonding: Effects of Surface Pretreatments (Smith, WaSU) Short Course Curriculum Development: Maintenance of Composite Aircraft Structures (Seaton, EdCC) Modeling Progressive Damage in Composite Aircraft Structures (Kennedy, OSU; to begin Spring 07)

41 Short Course Curriculum Development: Maintenance of Composite Aircraft Structures Primary Deliverables: 2005: Develop Terminal Course Objectives (TCO) and Course Description/Abstract Define curriculum modules 2006: Develop module content Develop course assessment tools Recommend FAA guidelines (precursor to policy) on training needs: Critical Composite Maintenance & Repair Issues

42 TCO, Module, and Content Development Achieved through close collaboration between Industry, Government, and Academia Workshops: FAA/Industry/Academia Workshop I (Seattle: 30 Nov- 2 Dec 2004; 64 attendees) Tele-conference (April 2005) FAA/Industry/Academia Workshop II (Chicago: Sept 2005; 61 attendees) Preliminary results 450 skills identified; 60+ TCOs; grouped into 11 major areas ( modules ) Consensus on course expectations between industrygovernment-academia (a major achievement!)

43 Final Results To be published in late 2006 Course content and other teaching tools will be available in public domain Written content, corresponding to TCOs Laboratory exercises and instructions Testimonials and Videos Updates available via AMTAS website:

44 Current AMTAS Projects Reliability-based Damage Tolerant Composite Design Methodologies (Lin, UW) Aeroservoelastic effects in Composite Aircraft (Livne, UW) Adhesive Bonding: Surface Characterization (Flinn, UW) Adhesive Bonding: Effects of Surface Pretreatments (Smith, WaSU) Short Course Curriculum Development: Maintenance of Composite Aircraft Structures (Seaton, EdCC) Modeling Progressive Damage in Composite Aircraft Structures (Kennedy, OSU; to begin Spring 07)

45 Current AMTAS Projects Modeling Progressive Damage in Composite Aircraft Structures Project PI: Prof. Tim Kennedy, Dept Mechanical Engineering, Oregon State University Specific project goals/deliverables to be finalized November 2006; project to begin Spring 2007 Expected to provide FEM-based progressive damage models: Stand-alone analyses and Eventual inclusion in Reliability-based Damage Tolerant Composite Design Methodology under development by K.Y. Lin

46 Educational Opportunity: AMTAS Composites Short Course AMTAS Institute on Adv Aircraft Composites Intended for practicing engineers Five-day intermediate-level course First offered Sept 06 with 23 students: Boeing (Seattle, Wichita, Long Beach): 14 C&D Zodiac: 5 Cytek (UK): 1 Trulife: 1 Wright-Patterson AFB: 1 Commercial Aviation Services: 1

47 AMTAS Short Course Curriculum and Instructors Day 1 Day 2 Day 3 Day 4 Day 5 Overview/New Develop Lin (UW), Stickler (Boeing) Tooling Dickson (Boeing) Analysis Methods Lin (UW) Manufacturing II McCarville (Boeing) Prod Lifecycle Management Richey/McPherson (Boeing) Materials Flinn (UW), Das (UW) Manufacturing I Das (UW), Soleiman (Boeing) Design Methodologies Eastman (Boeing) Test Methods Tuttle (UW), Pomering (INTEC) Nondestructive Inspection Swartz (FAA)

48 AMTAS Composites Short Course Next offering (tentatively) scheduled for March 2007 Updates posted at:

49 Knowledge Transfer: JAMS Meetings all AMTAS and CECAM participants JAMS 2005: May 2005, Wichita, KS ~100 attendees JAMS 2006: June 2006, Seattle, WA ~95 attendees JAMS 2007: (tentative) July 2006 Hughes Research Center Atlantic City, NJ

50 Knowledge Transfer: AMTAS Meetings Semi-annual meetings of AMTAS academic/industrial partners: 29 Jan 04: UW campus, 30 attendees 10 Nov 04: UW campus, 41 attendees 14 April 05: EdCC campus, 53 attendees 13 Oct 05: UW campus, 55 attendees 11 Apr 06: UW campus, 51 attendees 19 Oct 06: EdCC campus: 50 registrants Objectives Report/discuss AMTAS activities past/future Spring mtg focus: plan for future Fall mtg focus: present research results

51 AMTAS Staff & Contact Information Prof. Mark Tuttle, Director Prof. Kuen Lin, Co-Director Ms. Ellen Barker, Assistant to the Director

52 Thank you!