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1 Carbon Fibre Reinforced Magnesium and Aluminium Materials for Vehicle Structures Towards Affordable, Closed-Loop Recyclable Future Low Carbon Vehicle.

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Presentation on theme: "1 Carbon Fibre Reinforced Magnesium and Aluminium Materials for Vehicle Structures Towards Affordable, Closed-Loop Recyclable Future Low Carbon Vehicle."— Presentation transcript:

1 1 Carbon Fibre Reinforced Magnesium and Aluminium Materials for Vehicle Structures Towards Affordable, Closed-Loop Recyclable Future Low Carbon Vehicle Structures Hannah Constantin

2 2 Aim: to fabricate discontinuous carbon fibre reinforced magnesium composites for lightweight structures Objectives: Improve the creep resistance of unreinforced magnesium Incorporate recycled fibres Test feasibility of use of composite in powertrain applications

3 3 Overview Literature review Key challenges –Improve wettability of molten Mg on CFs –Reduce interfacial reactions –Achievable volume fractions Experimental methods –Fabricate composite coupons Characterisation and testing to identify further challenges Refining fabrication process Fabricate larger composites for further tests and realisation of components

4 4 Background Significantly increased creep resistance UD MgMC 30% volume fraction PAN CFs: E L = 104 GPa, E T = 35 GPa (epoxy E L = 74.8, E T = 5.8) Random MgMC 30% PAN CF: E = 59 GPa (epoxy 30 GPa) Variety of fabrication routes MaterialE L (GPa)E T (GPa) PAN CFs24010 AZ91D45 Epoxy44

5 5 Estimated mechanical properties (2) Mg–4Al–30%GrF longitudinal Mg–2Al–30%GrF long. Mg–30%GrF long. Mg AZ91 cast T6 Commercially pure Al cast Carbon steel as rolled Young’s Modulus (GPa) Density (g/cc) CES Edupack 2009 Material Young’s Modulus (GPa) Density ( -3 ) Specific Stiffness [m 2.s -2 (x10 9 )] Mg AZ91: 9Al–1Zn Al 6061: 1Mg– 0.8Si Steel A36: 0.7Cu–0.3C % PAN/AZ

6 Pressureless Infiltration (1) No external pressure Does not require expensive equipment Easy to control volume fraction Reinforcement homogeneously distributed

7 Pressureless Infiltration (2) Mg–9Al–1Zn + rCFs 900 o C Ramp rate 20 o C/min Air cooled Flowing Ar Mg + C reactions Al–10Mg + rCFs 900 o C Ramp rate 20 o C/min Air cooled Flowing Ar No infiltration

8 Contact angle θ < 90 o For Al on carbon fibres often > 140 o Depends on temperature 8 Wettability Sessile drop test

9 9 Fibre Coatings (1) TiN coating Al coating TiAlN coating Ti coating

10 10 Fibre Coatings (2) Increase wettability TiN, TiAlN, SiC, Al, Ti PVD Flat surface for experiments BSE image of TiN coated fibres 2500x magnification 5000x magnification SEM image of TiN coated fibres 5000x magnification

11 11 Gas Pressure Infiltration Demir 2004 Hufenbach

12 12 Limitations of Volume Fraction Corresponding fibre length (μm) assuming fibre Φ 7μm

13 13 What’s next?

14 14 Random Sequential Adsorption Model

15 15 Mechanical Testing, Characterisation, Fabrication of Larger Samples and Working Components Effective plastic strain SEM Tensile tests 3 point bend Indentation tests Shear tests Corrosion tests Creep tests

16 16 Summary Done: Researched C/Mg area Identified key challenges Next: Experiments to try to overcome challenges Fabricate a small sample Use computer model Later: Testing and characterisation of sample Fabrication of larger samples

17 17 Towards Affordable, Closed-Loop Recyclable Future Low Carbon Vehicles TARF-LCV Development of recyclable thermoplastic matrix composites for use in LCV body structures David Burn 19 th January 2012

18 18 Objectives Development of recyclable polymer matrix composites (PMCs) for LCV body structure Develop an effective approach for using short rCF in PMCs Study the effects of thermoplastic matrices on the mechanical properties of discontinuous PMCs Determine feasibility of using discontinuous PMCs as semi-structural /structural parts for LCVs

19 19 Background Fuel economy pushing towards lightweight vehicles Composites suited to this application ELV targets – 95% reuse and recovery of vehicle – 5% landfilled Highest potential recovery from thermoplastic polymers Drivers for thermosetting matrices Low viscosity (~10 3 lower than TPs) Low pressures and temperatures needed Currently more cost effective High strength and stiffness due to cross-linking Excellent encapsulation of fibres Low moisture absorption (less defects) Higher V f achievable ( % for TPs) Drivers for thermoplastic matrices Can be re-melted and reprocessed High toughness Generally better chemical resistance Generally high strain to failure Indefinite storage life Processing easily automated – lower cycle times Non-isothermal moulding Can be reconsolidated to eliminate voids or defects Can be thermally joined together

20 20 Polymer Matrices Discontinuous fibre composites transfer stress through the matrix material Properties more dependent on the matrix TPs generally have higher elongation to failure than thermosets Can a good fibre/matrix bond be achieved to enable stress transfer at the interface? How will the increased strain to failure affect the failure mode? Compare the data against toughened CF/Epoxies (lc/2) σfσf Stress concentrations at fibre ends ε σ CF/Epoxy CF/Thermoplastic? Kelly- Tyson Model

21 21 Specific Strength (x10 6 m 2 /s 2 ) Price (GBP/kg)

22 22 Thermoplastic Selection Water Absorption (24hr %) Shrinkage (%) Minimum Viscosity (Pa.s) Elongation at Break (%) Tensile Strength, 23ºC (MPa) Tensile Modulus, 23ºC (GPa) Max. Service Temperature (°C) EpoxyPPPBTpCBTPA-6PPSPEEKABSPCPEI Trade Name Prime 20 TOTAL 3270 Arnite T06200 Cyclics PBT Technyl A 205F Fortron 1140L6 Victrex 450G Cycolac GPM5500 Lexan 124R Ultem 1000 Microstructure SC AAA Processing Temperature (°C)

23 23 Cost vs. Tow Size TP Cost Recovery Normalised Strength vs. V f Recycled PolymerVirgin PolymerSaving Resin GradePelletsResinPellets (£/kg) (%) PP PBT ABS PC PA PEI PPS PEEK

24 24 Material Formats Pellets Powder Liquid Film / Sheet Commingled

25 25 Processing Routes

26 26 Processing Routes Pellets cheapest polymer format Melt impregnation and film stacking most viable options

27 27 Processing Routes Film format more expensive than pellets due to processing Film stacking with preform most viable option

28 28 Processing Routes Powder more expensive than pellets Powder coating and resin infusion most viable processing routes

29 29 Processing Routes Commingled tows most expensive Chopping into a mat most viable option Commingled Tow Plied Matrix Tow Cowoven Fabric Thermoplastic Matrix - Filament Carbon fibre reinforcement

30 30 Processing Routes ‘Total’ weighted mainly towards quality of part and ease of manufacture In-situ polymerisation, chopped commingled preforms and film stacking have the highest totals Format Stage Cost Quality of Part Ease of Manufacture Risk Weighted total Pellets Liquid Melt Impregnation PrepregProcessPart Pellets ExtrudeChop w/ FibresConsolidateProcessPart Pellets LiquidResin InfusionPrepreg / Part Film / Sheet Film Stacking SemipregConsolidateProcessPart Powder Powder Coating ConsolidationProcessPart Powder LiquidResin InfusionPrepreg / Part Commingled Chopped Prefrom ConsolidateProcessPart Liquid Resin Infusion Prepreg / Part 68378

31 31 Processing Routes – Random Materials CosmeticSemi-StructuralStructural DCFP DMC/BMCSMC ASMC Pellets in Mould Commingled Film StackingPre-impregnated Liquid (In-Situ Polymerisation) Powder Coating

32 32 In-Situ Polymerisation PA, PC, PEEK, PPS and PI all have reactive processing routes (in-situ polymerisation) However, limited supply of materials Avimid K and Avimid N (PI) NyRIM (PA-6) Cyclics CBT (PBT) Carried out trials to characterise Cyclics CBT Very small processing window Polymerised CBT (pCBT) properties poor, especially elongation to failure ~3% Interest from EPL – currently using a liquid CBT resin Supply chain for CBT unavailable Need a supplier to continue research

33 33 Differential Scanning Calorimetry – Cyclic CBT Heat Flow (W/g) Time (min) Peak due to crystallisation, polymerisation occurs simultaneously at this point Holding at 190ºC Cooling at 5ºC/minReheating at 10ºC/min Melting of the polymerised CBT Crystallinity calculation: Low crystallinity generally gives better mechanical properties

34 34 Differential Scanning Calorimetry – Cyclics CBT Processing temperature Polymerisation and crystallisation simultaneous or consecutive based on temperature Temperatures <190ºC, polymerisation incomplete and resulting ‘polymer’ is unusable Processing temperatures above 200ºC causes crystallisation to occur during cooling Degree of crystallinity can be controlled Holding time Small effect on the degree of crystallinity Polymerisation cannot complete in less than 20mins Cooling rate No significant effect on the degree of crystallinity Pre-drying CBT Decreases crystallinity of final polymer by approximately 5% Slightly delays polymerisation and crystallisation

35 35 Current Work Polypropylene / DCFP preform 500gsm preform – 17% V f Polymer flows around preform Poor encapsulation Polypropylene / Recycled CF mat Uniform mat – guaranteed global V f 100gsm recycled fibre mat – 13 – 20% V f Polymer penetrates mat Incrementally increasing V f to find limit To date highest V f is 20% 25% V f reported in the literature 3 point bending - flexural modulus of around 6-7GPa for random mat Rule of mixture equation predicts 14GPa

36 36 Current Work Limited V f due to film stacking approach Initial stacking resulted in dry sections Processing was modified to produce ‘composite film’ These were stacked and pressed Optical microscopy shows good wet-out Fibres still appear dry on the fracture surface SEM needed to assess encapsulation Matched-die mould required to improve properties Vacuum assisted Improve fibre encapsulation

37 37 Future Work Commingled Drag fibre through bath Co-extrude Powder coating Fluidised bed Prepreg route Similar to HexMC Use a UD fabric and chop to make high V f SMC Further studies with in-situ polymerisation and low viscosity polymers Working with Davide de Focatiis and Derek Irvine Carbon Fibre Spool Resin Bath Take-up Roll Squeeze Rollers Balance Bars Tm of Resin Air Quench Device Carbon Fibre Spool Tow Spreader Infra-red Oven Take-up Roll Ionised Air Dry Air Input Charging Medium Porous Plate Vacuum

38 38 Future Work Need repeatable processing route Test other polymers What are the effects of high strain to failure of the matrix? How is the composite affected by cyclic testing? Fatigue endurance Creep behaviour Crashworthiness Ballistic impact testing What are suitable applications based on the Vf achievable? Cost modelling to assess new processing routes Demonstrator part May need some industrial partnership EPL interested in CBT

39 39 Future Work WP1 – Feasibility study 1.1 – Find repeatable method for processing composites 1.2 – Process PP using UniFilo, DCFP and fabrics 1.3 – Process and compare selection of TPs 1.4 – Use data from processing to validate model WP2 – Development of model and characterisation of thermoplastic matrices 2.1 – Develop FE model for TP composites 2.2 – Study the effects of binder/sizing/surface treatments on interfacial adhesion 2.3 – Joining of thermoplastics 2.4 – Carry out work to develop processing of low viscosity TPs??? WP3 – Demonstration of technology Demonstrator Part Would need some industrial support

40 Thursday, January 19 th 2012Progress Report David Burn 40 Thank you for your attention.

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