Composite Materials for Aircraft

Composite Materials for Aircraft Structures: A Brief Review of Practical Application Jared W Nelson, PhD Candidate Department of Mechanical and Industrial Engineering Montana State University ME 480 Introduction to Aerospace, S p rin g 2010 pg Introduction • Com p osite materials are used more and more for p primary structures in commercial, industrial, aerospace, marine, and recreational structures Design and Analysis of Aircraft Structures 13-2 From Last Time • Composite parts used for aircraft applications are defined by – Material, process, and manufacturing specifications. – Material allowable (engineering definition). • All of these have a basis in regulatory requirements. • Most efficient use of advanced composites in aircraft • Most efficient use of advanced composites in aircraft structure is in applications with – Highly loaded parts with thick gages. – High fatigue loads (fuselage and wing structure, etc). – Areas susceptible to corrosion (fuselage, etc). Critical weight reduction (empennage wings fuselage etc) – Critical weight reduction (empennage , wings , fuselage , etc) . • Use must be justified by weighing benefits against costs. Design and Analysis of Aircraft Structures 13-3 Composition of Composites • Good shear properties Hi h t th • High strength Fiber/Filament Reinforcement CompositeMatrix • Good shear properties • Low density • Thermoset & • Hi g h s t reng th • High stiffness • Low densit y • High strength • High stiffness • Good shear properties Thermoplastic • Epoxy, Polyester, PP, Nylon, Ceramics, etc. y • Carbon, Glass, Aramid, etc • Low density • Anisotropic! Design and Analysis of Aircraft Structures 13-4 Overview • Micromechanics Study of mechanical behavior of a composite material in terms of – Study of mechanical behavior of a composite material in terms of its constituent materials • Ply Mechanics – Study of mechanical behavior of individual material plies based on variations from global coordinate system • Macromechanics – Study of mechanical behavior utilizing ply mechanics of a homogenized composite material • Failure Theories • Failure Theories Design and Analysis of Aircraft Structures 13-5 CADEC: Introduction Compliment to text: Barbero, EJ. Introduction to Composite Mt il D i T l & F i 1999 M a t er i a l s D es i gn; T ay l or & F ranc i s, 1999 . Software free online—search keywords CADEC & Barbero Design and Analysis of Aircraft Structures 13-6 Micromechanics: Assumptions • Lamina: – Macroscopically homogeneous – Linearly elastic Linearly elastic – Macroscopically Orthotropic – Initially stress free Fibers: • Fibers: – Homogeneous – Linearly elastic – Isotropic/Orthotropic – Regularly spaced – Perfectly aligned • Matrix: Carbon/epoxy (AS4/3501-6) composite (Vf=.70) Matrix: – Homogeneous – Linearly elastic – Isotropic Assumptions in Micromechanics of Composites Design and Analysis of Aircraft Structures – Assumptions in Micromechanics of Composites 13-7 Micromechanics: Rule of Mixtures V f,max approximately 78% Common range = 55-67% Design and Analysis of Aircraft Structures 13-8 Micromechanics: Determining Properties Design and Analysis of Aircraft Structures 13-9 Micromechanics: Rule of Mixtures (E 1 ) Design and Analysis of Aircraft Structures 13-10 [...]... Analysis of Aircraft Structures 13-23 Ply Mechanics: CADEC Design and Analysis of Aircraft Structures 13-24 Ply Mechanics: Compliance Plane Stress Design and Analysis of Aircraft Structures 13-25 Ply Mechanics: CADEC Design and Analysis of Aircraft Structures 13-26 Ply Mechanics: Transformations Design and Analysis of Aircraft Structures 13-27 Ply Mechanics: CADEC Design and Analysis of Aircraft Structures... Properties Design and Analysis of Aircraft Structures 13-11 Micromechanics: Rule of Mixtures (E2) Design and Analysis of Aircraft Structures 13-12 Micromechanics: Determining Properties Design and Analysis of Aircraft Structures 13-13 Micromechanics: Rule of Mixtures (ν12) Design and Analysis of Aircraft Structures 13-14 Micromechanics: Determining Properties Design and Analysis of Aircraft Structures 13-15... Analysis of Aircraft Structures 13-20 Micromechanics: Determining Properties Design and Analysis of Aircraft Structures 13-21 Micromechanics: Thermal & Electrical Cond Design and Analysis of Aircraft Structures 13-22 Ply Mechanics • So what happens if we vary the fiber direction angle away from the 1-direction? y • CADEC uses Micromechanics results and fiber angle – – – – Plane Stress Transform stress/strain... of Aircraft Structures 13-16 Micromechanics: Other Methods & Strengths Design and Analysis of Aircraft Structures 13-17 Micromechanics: Halpin-Tsai (E2) Halpin-Tsai: “Semiempirical (1969) version to obtain better prediction”—Barbero ζ ≡ empirical curve fitting parameter, commonly 2a/b Design and Analysis of Aircraft Structures 13-18 Micromechanics: Determining Properties Design and Analysis of Aircraft. .. Design and Analysis of Aircraft Structures 13-29 Ply Mechanics: CADEC Design and Analysis of Aircraft Structures 13-30 Ply Mechanics: Stress-Strain Relationships • Stress-Strain Relationship: σ ij = Cij ε ij • With 3 planes Cij has 81 terms, but since: and: ε ij = ε ji only 36 terms σ ij = σ ji • Orthotropic material (2 planes of symmetry) reduces to terms: t 9t Design and Analysis of Aircraft Structures... Material Design and Analysis of Aircraft Structures 13-32 Macromechanics • What if there are multiple lamina at differing angles? • CADEC uses Micromechanics and Ply mechanics to determine: – – – – – – Stiffness and Compliance Equations Laminate Moduli Global and Material Stresses and Strains Strains and Curvatures Thermal and Hygroscopic loads yg p For both Intact and Degraded materials • Assumes: ssu es... symmetry (known as the midplane) the code may be shortened by listing only the angles from the arrow side to the midplane A subscript “S” is used to indicate that the code for only one half of the laminate is shown Design and Analysis of Aircraft Structures 13-34 Shorthand Laminate Orientation Code Fabrics and Tapes and Fabrics [(45)/(0)/(45)] Midplane Fabrics [(45)/0(-45)/90] Midplane Tapes & Fabrics •... tape plies • When the laminate is symmetrical and has an odd number of plies, the center ply is overlined to p indicate that it is the midplane Design and Analysis of Aircraft Structures 13-35 Macromechanics: CADEC Design and Analysis of Aircraft Structures 13-36 ... Hygroscopic loads yg p For both Intact and Degraded materials • Assumes: ssu es – – – – Plane sections remain plane Symmetry about a neutral surface No shear coupling Perfect bonding Design and Analysis of Aircraft Structures 13-33 Shorthand Laminate Orientation Code Tapes or Undirectional Tapes [45/0/-45/902 /-45/0/45 [45/0/-45/90] s Tapes or undirectional tapes • Each lamina is labeled by its ply orientation . Composite Materials for Aircraft Structures: A Brief Review of Practical Application Jared W Nelson, PhD Candidate Department. regulatory requirements. • Most efficient use of advanced composites in aircraft • Most efficient use of advanced composites in aircraft structure is in applications with – Highly. costs. Design and Analysis of Aircraft Structures 13-3 Composition of Composites • Good shear properties Hi h t th • High strength Fiber/Filament Reinforcement CompositeMatrix • Good shear