Introduction to Aerospace Engineering

Transcription

1 Introduction to Aerospace Engineering Lecture slides Challenge the future 1

2 Manufacturing aspects Metals & Composites Faculty of Aerospace Engineering Delft University of Technology Challenge the future

3 Learning objectives Student should be able to Metals Describe the three main manufacturing processes in metals List typical processes for each category Composites List typical manufacturing processes in composites Manufacturing aspects 2 26

4 Metals What are typical Properties of Metal alloys you can use to create a metal component or product? Melting you can liquify a metal (alloy) Plastic deformation at Room temp. deforming by high forces Manufacturing aspects 3 26

5 Metals Categories of manufacturing processes Liquid casting Shearing Forming Manufacturing aspects 4 26

6 Metals Shearing processes Solid state cutting & milling processes Large components with small geometrical tolerances possible Geometrical tolerances Definition: Maximum variation allowed in form or positioning Type of tolerance Form control Flatness Positioning Perpendicular/parallel Etc. Manufacturing aspects 5 26

7 Metals Typical forming processes Bulk material (hot) Extrusion Sheet/plate material (RT) Bending Drawing Drawing Forging Rolling Manufacturing aspects 6 26

8 Metals Forming process Consider sheet bending Elastic spring back Manufacturing aspects 7 26

9 Metals Forming process Sheet bending (elastic spring back) Less spring back for low yield strength Design requires high yield strength!! After springback Manufacturing aspects 8 26

10 Metals Forming process Consider forging process Geometrical tolerances obtained by subsequent machining/milling Example applications Manufacturing aspects 9 26

11 Metals Forging Example of formation of residual stresses Manufacturing aspects 10 26

12 What are composite properties you can use to manufacture composite parts? Composites consist of fibres and resin/polymer Fibers (long): hardly elongate; you have to place them What about short fibers? Resin: Thermoplastic: you can soften the polymer by heating Thermoset: the resin is a liquid before curing Manufacturing aspects 11 26

13 Categories of manufacturing processes Placement of fibres Dry condition Wet condition Pre-impregnated Manufacturing aspects 12 26

14 Filament winding Typical product Pressure vessel Textile appearance Manufacturing aspects 13 26

15 Filament winding Placement of fibres Bound by initial orientation and friction No free variable orientation possible Mould called MANDREL Removable Solvable, collapsable, tapered Used as liner Air-water tight Shapes Closed shapes (cylinder like) No open shapes (bathtub like) Manufacturing aspects 14 26

16 Filament winding Windings: Hoop α i = 90 Helical α i = ± n Polar α i 0 Manufacturing aspects 15 26

17 Pultrusion Reinforcement: Roving - Strand - UD material most seen Chopped strand (fibre mat) Woven Matrix: Thermoset: e.g. Polyesters, vinyl esters How to get the fibre material loaded Manufacturing aspects 16 26

18 Pultrusion Machine Time to change product is high Manufacturing aspects 17 26

19 Lay-up Lay-up by hand = Hand Lay-up Lay-up by machine = Tape Laying Manufacturing aspects 18 26

20 Lay-up Lay-up by machine = Tape Laying Manufacturing aspects 19 26

21 Lay-up Tape laying vs. Hand lay-up More accurate lay-up Better mechanical properties Less differences between identical parts More expensive Often used for high end products, e.g. space technology Size can be large, limited by Time needed for impregnation-curing Autoclave size (possibly) Dry lay-up is followed by impregnation & curing Wet lay-up is followed by curing Manufacturing aspects 20 26

22 Resin Transfer Moulding (RTM) Resin Transfer Moulding (RTM) Place dry fibres in stiff mould Close mould system Use pressure difference to draw resin through mould cavity Vacuum Infusion Place dry fibres on stiff mould Close mould with flexible film Use vacuum to compress laminate and to draw resin through reinforcement Manufacturing aspects 21 26

23 Resin Transfer Moulding (RTM) Resin Transfer Moulding (RTM) Pressure injection: P 1 >1bar, P 2 =1bar Vacuum Assisted Resin Transfer Moulding (VARTM) Pressure difference: P 1 >1bar, P 2 <1bar Vacuum Infusion Pressure difference: P 1 =1bar, P 2 <1bar : Manufacturing aspects 22 26

24 Vacuum infusion Examples Contest 55 Eaglet rudder Manufacturing aspects 23 26

25 Thermoplastic vs. Thermoset A - Thermoset resin: a) Liquid component A + liquid component B b) Impregnate fibers c) Chemical reaction + d) Solid matrix a) Solid matrix B - Thermoplastic resin: b) Melting step c) Impregnate fibers/press form part d) Cooling step e) Solid matrix Manufacturing aspects 24 26

26 Thermoplastic vs. Thermoset Thermoplastic composites: Rapid manufacturing Recyclable Weldable High temperatures and pressures However: Melt processing limits achievable thickness Wind turbine blades are too large for pressing Melt processing of thermoplastic composites not suitable for manufacturing of wind turbine blades Manufacturing aspects 25 26

27 Summary Manufacturing is strongly related to material properties Type of products (shape) depends on materials and their processes Metals Plastic deformation, melting, cutting Forming, casting and machining processes Composites Two different components: resin & fibers Resin: thermoplastic or thermoset Fibers: almost no deformation, placing, orienting, drifting Manufacturing aspects 26 26