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

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

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

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 Overview Literature review Key challenges Experimental methods
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 Background Significantly increased creep resistance
UD MgMC 30% volume fraction PAN CFs: EL = 104 GPa, ET = 35 GPa (epoxy EL = 74.8, ET = 5.8) Random MgMC 30% PAN CF: E = 59 GPa (epoxy 30 GPa) Variety of fabrication routes Material EL (GPa) ET (GPa) PAN CFs 240 10 AZ91D 45 Epoxy 4

5 Estimated mechanical properties (2)
CES Edupack 2009 Estimated mechanical properties (2) 200 100 50 20 10 Carbon steel as rolled Mg–4Al–30%GrF longitudinal Mg–2Al–30%GrF long. Mg–30%GrF long. Young’s Modulus (GPa) Commercially pure Al cast Material Young’s Modulus (GPa) Density (g.cm-3) Specific Stiffness [m2.s-2 (x109)] Mg AZ91: 9Al–1Zn 45 1.74 25.86 Al 6061: 1Mg–0.8Si 70 2.71 25.83 Steel A36: 0.7Cu–0.3C 210 7.8 26.92 30% PAN/AZ91 59 33.90 Mg AZ91 cast T6 Density (g/cc)

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

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

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

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

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

11 Gas Pressure Infiltration
Demir 2004 Hufenbach 2006

12 Limitations of Volume Fraction
𝑉 𝑓 = 2𝑙𝑛𝜆 𝜆 Parkhouse, J. G. and Kelly, A., The random packing of fibres in three dimensions. Proceedings of the Royal Society London A 451, 737 – 746 𝑉 𝑓 = 2𝑙𝑛𝜆 𝜆 Where λ = aspect ratio Evans, K. E. and Gibson, A. G., Prediction of the maximum packing fraction achievable in randomly orientated short-fibre composites. Composites Science and Technology 25, 149 – 162 𝑉 𝑓 = 𝑘𝑑 𝑙 Where k = 5.3 d = fibre diameter l = fibre length Corresponding fibre length (μm) assuming fibre Φ 7μm

13 What’s next?

14 Random Sequential Adsorption
Model

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 Summary Done: Next: Later: 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 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 19th January 2012

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 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 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 Drivers for thermosetting matrices Low viscosity (~103 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 Vf achievable ( % for TPs) 

20 Stress concentrations at fibre ends
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) σf Stress concentrations at fibre ends ε σ CF/Epoxy CF/Thermoplastic? Kelly- Tyson Model

21 Specific Strength (x106 m2/s2)
Price (GBP/kg)

22 Thermoplastic Selection
Tensile Modulus, 23ºC (GPa) 3.2 1.4 2.7 2.2 7.6 3.7 2.4 2.3 3.4 Max. Service Temperature (°C) 122 110 195 185 260 315 70 170 Epoxy PP PBT pCBT PA-6 PPS PEEK ABS PC PEI 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 A Processing Temperature (°C) -- 190 250 290 310 400 220 245 320 Tensile Strength, 23ºC (MPa) 75 33 55 56.1 85 125 100 35 65 105 Elongation at Break (%) 4.1 150 80 0.7 50 1.9 45 20 100 60 Water Absorption (24hr %) 0.08 0.02 1.2 0.01 0.07 0.2 0.1 0.26 Shrinkage (%) 1.83 1.5 5 0.7 0.6 1 0.5 Minimum Viscosity (Pa.s) 0.5 3000 500 0.018 320 29 350 100 230 600

23 Normalised Strength vs. Vf
Cost vs. Tow Size TP Cost Recovery Recycled Polymer Virgin Polymer Saving Resin Grade Pellets Resin (£/kg) (%) PP 1.14 1.79 36 PBT 1.01 1.50 33 ABS 1.15 2.33 51 PC 1.25 3.10 60 PA-6 1.17 3.08 62 PEI 6.95 12.63 45 PPS 6.17 12.34 50 PEEK 25.84 64.60 Normalised Strength vs. Vf

24 Material Formats Pellets Powder Liquid Film / Sheet Commingled

25 Processing Routes

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

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

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

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

30 Processing Routes Format Stage Cost Quality of Part Ease of Manufacture Risk Weighted total 1 2 3 4 5 Pellets Liquid Melt Impregnation Prepreg Process Part Extrude Chop w/ Fibres Consolidate 6 Resin Infusion Prepreg / Part 7 Film / Sheet Film Stacking Semipreg 8 Powder Powder Coating Consolidation Commingled Chopped Prefrom ‘Total’ weighted mainly towards quality of part and ease of manufacture In-situ polymerisation, chopped commingled preforms and film stacking have the highest totals

31 Liquid (In-Situ Polymerisation)
Processing Routes – Random Materials Cosmetic Semi-Structural Structural DCFP DMC/BMC SMC ASMC 10 15 20 25 30 35 40 45 50 55 + Pellets in Mould Commingled Film Stacking Pre-impregnated Liquid (In-Situ Polymerisation) Powder Coating

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

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

36 Current Work Limited Vf 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 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 Vf 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 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 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 Thank you for your attention.
Thursday, January 19th 2012 Progress Report David Burn


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