Composites Manufacturing

Transcription

1 Composites Manufacturing Session delivered by: Dr. Srikari S. 1

2 Session Objectives At the end of the session the delegates will get an overview on Manufacturing Processes Polymer Matrix Composites (PMCs) Metal Matrix Composites (MMCs) Ceramic Matrix Composites (CMCs) 2

3 Polymer Composite Manufacturing Processes When considering each process, think about the equipment required, and what important process parameters may need to be specified. Distinctions between Batch Processes: Process stages occur sequentially in time to produce a single part. Continuous Processes: Product is generated continuously, passing through geographic stages. 3

4 Basic necessities for any process Reinforcement Shaping - to define initial architecture of reinforcement. Part Shape Definition Matrix Infusion - compressing reinforcement, or maybe prepreg, to final shape of the part. - usually done within a mould, or die. - to fully immerse the reinforcing fibres in the polymer matrix. - should expel all air, or voids, from part. Matrix Solidification - to provide for the necessary cure of a thermoset, or solidification of a thermoplastic. 4

5 Material Forms PEMP Woven: Series of Interlaced yarns at 90 to each other Knit: Series of Interlooped Yarns Braided: Series of Intertwined, Spiral Yarns Nonwoven: Oriented fibers either mechanically, chemically, or thermally bonded Components of a Woven Fabric 5

6 Wet Hand Lay-up Dry reinforcement and catalysed resin are draped over a one-sided mould. The resin is forced to impregnate the reinforcement using a roller. A number of layers can be built up in sequence. Resin curing is initiated, and the part removed when sufficiently rigid. Applications: Standard wind turbine blades, boats, etc. 4) Resin Cure PEMP 1) Placement of Dry reinforcement 2) Resin Wetting 3) Repeated Application of Layers 6

7 Wet Hand Lay-up PEMP Part manufacture can be completed in several layers, with careful consideration of material compatibility, and sequential cure. Common modifications include: Vacuum bagging after lay-up Pre-impregnation of fabric 7

8 Spray-up Process PEMP Glass Roving Fig. 1 Bulk Resin Catalyst 1. Glass roving, bulk resin and catalyst are fed to the spray gun. 2. The mixture is sprayed over a mould, defining part shape. 3. Resin cure is initiated, and the part removed when rigid. 8

9 Equipment used in Spray-up PEMP Part being sprayed-up Full dispensing system Part removed from mould. Chopper Roving Atomized resin and catalyst 9

10 Merits/demerits of Spray-up Process Relatively fast, and simple method for applying reinforcement and matrix to a mould, in one step. Moderate equipment expenses. Limited to random chopped fibre architecture (limits structural properties). Must be careful to maintain a clean, and healthy working environment. Applications are lightly loaded structural panels, e.g. caravan bodies, truck fairings, bathtubes, small boats, etc. 10

11 Prepreg Lay-up PEMP 1) Laminate Assembly 3) Resin Melts, Layup Consolidates 5) De-moulding 2) Applied Pressure and Heat 4) Resin Cures Prepregs are reinforcing fabrics supplied with solid catalysed resin present. Layers are cut to shape, and placed on the mould, which defines part shape. Heat and pressure are applied, the resin melts, and the part consolidates. Temperature is raised further to initiate cure. 11

12 TS Prepreg Lay-up PEMP Sheet of carbon fibre prepreg Motorcycle fairing Aerospace parts Vacuum-bagged part ready for oven 12

13 TP & TS Prepreg Lay-up PEMP Application to large aerofoil skins: Used for high performance parts, manufactured in small numbers. 13

14 Vacuum-Bag Molding Was developed for making a variety of components, including relatively large parts with complex shapes. Applications: Large cruising boats, racecar components, etc. Vacuum bagging Kevlar laminate 14

15 Pressure-Bag Molding Pressure bag process is virtually a mirror image of vacuum bag molding. Applications are sonar domes, antenna housings, aircraft fairings, etc. 15

16 Autoclave Molding Autoclave molding is similar to both vacuum bag and pressure bag molding. Applications are lighter, faster and more agile fighter aircraft, motor sport vehicles. 16

17 Autoclave temp./pressure cycle PEMP 17

18 TS Compression Moulding PEMP 1) Placement of Charge 3) Squeeze to final dimensions 5) De-moulding 2) Mould Closure 4) Resin Cure Catalysed resin and chopped glass strands are supplied as a premixed compound. e.g. Bulk Moulding Compound (BMC), or Sheet Moulding Compound (SMC). As heat and pressure applied within mould, compound flows, taking shape. Resin cure is initiated and the part removed when sufficiently rigid. 18

19 TS Compression Moulding PEMP SMC being cut to size, before placed in a mould. Two-sided, rigid moulds are required. Moulds require heating to initiate cure. 19

20 TS Compression Moulding Relatively fast method, suitable for automation. Significant equipment expense, including 2-sided moulds and press. Moulds must withstand large clamping pressures. PEMP 20

21 Liquid Composite Moulding (RTM) PEMP 1) Preform Manufacture 3) Resin Injection 5) De-moulding 2) Preform Compression 4) Resin Cure The dry reinforcement, or preform, is enclosed in some form of mould, which fully defines the shape of the part. Resin flows under pressure through the porous preform, expelling all air. At some stage resin cure is initiated, and the mould is opened once the part has achieved significant rigidity. 21

22 Resin Transfer Molding (RTM) Is commonly used in the aerospace and automotive industry. The process consists of mixing resin with a hardener (or initiator) and injecting the combination into a mold which contains dry fibers. The mix of resin & hardener is then injected at a low pressure of 5 psi (34.5 kpa) into a mold. The resulting part is cured at room temperature for several hours. Advantages Low pressure 5 psi (34.5 kpa) Fiber loadings are typically around 50-60% (Volume) Preform architecture can be very complicated PEMP 22

23 Liquid Composite Moulding PEMP Benefits - Net-shape manufacture - Control of fibre architecture - Good surface finishes Preform placed in mould Stack of preforms 23

24 Diaphragm Forming Example products, TPs reinforced with: PEMP Carbon Fibre Glass Fibre 24

25 TS Pultrusion (Thermo-Set Pultrusion) PEMP Dry roving or fabrics are drawn through a catalysed resin bath. Wet mixture is drawn through die. Excess resin runs off. Heat added to cure. Heating Section [4] Possible Cooling Section Possible cooling. Excess Resin 25

26 TS Pultrusion Equipment PEMP Fibre creel Cut-off Die sections Resin bath Cooling 26

27 Merits of TS Pultrusion Reinforcement used in forms other than roving Currently used to produce large quantities of thermoset composites, in a wide variety of cross-sections. Good control can be obtained on resulting fibre architecture. Pulforming is similar to pultrusion in many ways can also be used to form straight or curved, with changing shapes and volumes. A typical pulformed product is a curved reinforced plastic car spring. 27

28 Filament Winding PEMP Dry roving is drawn through a catalysed resin bath. Wet roving is wound under tension on to a mandrel, or shell. Mechanical control of the guidance eye applies reinforcement in predetermined pattern. 28

29 Equipment used in Thermoset Filament Winding PEMP Whirling-Arm Racetrack Lathe 29

30 Products of Thermoset Filament Winding Pipes Pressure vessel 8 m dia. Chimney stack 30

31 Injection Moulding Direct Mixing Injection Moulder Mould Matrix Short Fibres Fibre Resin Pellets [3] Raw materials are supplied and premixed, in the injection moulder. Short fibre reinforced melt is injected into a mould. Mould fills, and, the final fibre orientation heavily depends on flow. Part solidifies, and is ejected. 31

32 Injection Moulding Small Extruder used to prepare fibre loaded TP pellets. Injection Moulder utilised for short fibre reinforcement. Applications: Auto parts, vanes, engine cowling defrosters and aircraft radomes. 32

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34 Manufacturing Methods of MMCs Melting process Infiltration of reinforcements by squeeze casting, vacuum or pressure infiltration Reaction infiltration of fiber or particle preform Processing of precursor materials by stirring particles in metal matrix followed by sand casting, permanent mold casting or high pressure die casting Powder metallurgy process Joining and welding of semi manufactured products 34

35 MMC Manufacturing Melt Stirring [29] Gas Pressure Infiltration [29] 35

36 Direct and Indirect Squeeze Casting 36

37 Manufacturing methods of CMCs A. CONVENTIONAL TECHNIQUES: 1. Cold pressing and Sintering 2. Hot pressing 3. Reaction bonding process 4. Combined Hot pressing and Reaction bonding method B. NOVEL TECHNIQUES: 1. Liquid Infiltration 2. Directed Metal Oxidation (Dimox TM /Lanxide TM ) C. IN-SITU CHEMICAL REACTION TECHNIQUES: 1. Chemical Vapor Deposition (CVD) 2. Chemical Vapor Impregnation (CVI) 3. Sol-Gel and Polymer Pyrolysis 37

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42 Costs of Composite Manufacture Material costs -- higher for composites Constituent materials (e.g., fibers and resin) Processing costs -- embedding fibers in matrix not required for metals; Carbon fibers order of magnitude higher than aluminum Design costs -- lower for composites Can reduce the number of parts in a complex assembly by designing the material in combination with the structure Increased performance must justify higher material costs 42

43 Effect of manufacturing process on component cost 43

44 Material s Selection Property Determination Prototype Evaluation COMPOSITE COMPONENT Design Feasibility NDT Manufacturing Technology Detailed Analysis 44

45 Process Selection Several factors should be considered before selecting the manufacturing process for a particular part; PEMP Materials - reinforcing, and matrix systems Reinforcing architecture required Complexity of part geometry Number to be manufactured How quickly they are to be manufactured These are important for all manufacturing processes, and even more so for composite materials Ideally, structural design of the product, and design of the required manufacturing process should be completed using a concurrent approach. 45

46 Some Manufacturing Techniques 46

47 Summary Manufacturing process for different types of composites is explained. The effect of manufacturing process on the properties have been discussed. The selection of manufacturing process and the reliability factors of composites have been discussed. THANK YOU 47