The Determination of the Fibre Volume Fraction in Natural Fibre Composites Richard Cullen and John...

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  • The Determination of the Fibre Volume Fraction in Natural Fibre CompositesRichard Cullen and John SummerscalesAdvanced Composites Manufacturing CentreUniversity of PlymouthUniversity of Warwick, 20 April 2004

    Advanced Composites Manufacturing Centre - University of Plymouth

  • Elastic modulus of composite calculated by rule-of-mixturesneglect contribution of matrixEc = ~ L O VF EFLfibre length distribution factorO fibre orientation distribution factorVFfibre volume fractionEFelastic modulus of fibre

    Advanced Composites Manufacturing Centre - University of Plymouth

  • Determining Vf is problematicfibres float in waterfibres are hygroscopicweight is function of moisture content4.6% loss in jute yarn dried 60C for 30 mincross-sectional area of the fibresnot normally round

    Advanced Composites Manufacturing Centre - University of Plymouth

  • Determination of Vftow counting/areal weightdirect weighingdensity gradientArchimedes principleresin burn-offthermo-gravimetric analysischemical digestionmicroscopy

    Advanced Composites Manufacturing Centre - University of Plymouth

  • Vf by tow counting/areal weighttow counting for UD composites in an open-ended mould Grafil Test Method 302.24 fabric areal weight in a moulding of known thickness CRAG method 1000-2

    Advanced Composites Manufacturing Centre - University of Plymouth

  • Calculate volume fractionfrom fabric areal weight Vf = j AF / f t

    j number of layers of fabricAF areal weight of fabric (kg/m2)f density of fibre (kg/m3)tthickness of laminate (m)

    Advanced Composites Manufacturing Centre - University of Plymouth

  • Vf by direct weighinga closed mould is usedno fibre is lost in the moulding flashmass fraction after fabrication = mass of fibre/mass of the composite.accurate densities needed to convert the mass fraction to a fibre volume fraction. Grafil Test Method 302.13

    Advanced Composites Manufacturing Centre - University of Plymouth

  • Vf by density gradientobserve the level to which the test specimen sinks in a column of liquid when the density of liquid changes uniformly with height.absorption of liquid may complicate the analysis when natural fibres are under test Grafil Test Method 301.12

    Advanced Composites Manufacturing Centre - University of Plymouth

  • Vf by Archimedes principleweight measurementsin air and in waterabsorption of liquid may complicate the analysis when natural fibres are under test. Grafil Test Method 301.21 CRAG methods 800/1000-1

    Advanced Composites Manufacturing Centre - University of Plymouth

  • Densitydensity of resin typically 1100 kg/m3density of fibre typically 1600 kg/m3 resolution of 5 mg/cm3 for 1%Vf CRAG method 800 for density of FRP 1g or more weighed in air and in fluidaccuracy 0.2% desirable for Vf and Vvimmersion fluid at 23 2C

    Advanced Composites Manufacturing Centre - University of Plymouth

  • Density of jutedried 60C for 30 minweighed in air immediatelyimmersed and degassed in fluid -990 mbar water : -500 mbar acetoneweighed in fluid = 1.6690.037 in water/Ilfotol at 22.4C = 1.6520.037 in acetone at 20.3C data from Richard Cullen image from Jean-Philippe le Nours

    Advanced Composites Manufacturing Centre - University of Plymouth

  • Vf by resin burn-offinappropriate for natural fibre compositesoven at 580-600C until constant weightboth components of the composite will burn CRAG method 1000-3c

    Advanced Composites Manufacturing Centre - University of Plymouth

  • Vf by TGA:Thermo-Gravimetric AnalysisTGA measures weight changes in a material as a function of temperature (or time) under a controlled atmosphereprincipal uses include measurement of material thermal stability & composition. http://www.tainst.com/products/tga.html

    Advanced Composites Manufacturing Centre - University of Plymouth

  • Vf by TGA: flax fibresprimary decomposition peak 55-91% weight loss between 315-362Csecondary decomposition peak2-33% weight loss between 406-465Cash 4-9 % by weight HSS Sharma et al: Queens-Belfast/DANIThermochimica Acta, 1988, 132, 101-109.J Textile Institute, 1996, 87(2), 249-257.J App Polym Sci, 2000, 75, 508-514.

    Advanced Composites Manufacturing Centre - University of Plymouth

  • Vf by TGA: flax/HDPEPure flaxdecomposition starts c.200-210C3% wt loss by 385C>400C degradation slows (ash)Pure HDPEdegradation starts c.410-430C9% wt loss by 490C T Powell et al, Engineering properties of flax fiber and flax fiber-reinforced thermoplastic in rotational moulding, ASAE/CSAE meeting, Saskatchewan, September 2002.

    Advanced Composites Manufacturing Centre - University of Plymouth

  • Vf by TGA: sisal/starchhemicellulose & cellulose glycosidic linksdecomposition peak at 300Calpha-cellulosedecomposition peak at 360Clignindecomposition between 200-500Cmaximum at 350C VA Alvarez and A Vzquez , 2004 Polymer Degradation and Stability, 84(1), 13-21

    Advanced Composites Manufacturing Centre - University of Plymouth

  • Vf by chemical digestionsulphuric acid and hydrogen peroxide Grafil Test Method 302.56 CRAG method 10003anitric acid CRAG method 1000-3bdifferent chemicals for natural fibres ?microwave acid digestion bomb ? Journal of Materials Science Letters ?

    Advanced Composites Manufacturing Centre - University of Plymouth

  • Vf by microscopyoptical or electron microscopy with computer image analysisfor natural fibres enhance the contrast polarising filters or staining techniquesimage splitting eyepieceto determine individual fibre diameters Grafil Test Method 102.13

    Advanced Composites Manufacturing Centre - University of Plymouth

  • Vf by optical microscopycoarse polish (recommended)gives better contrast but manual intervention to eliminate scratchesfine polish removes scratches but significantly lowers contrastmanipulate with Photoshop or similarto optimise contrastanalyse with ImageJ http://rsb.info.nih.gov/ij/

    Advanced Composites Manufacturing Centre - University of Plymouth

  • Use of ImageJ softwareoriginal optical microscopy imageoptimise contrast in Photoshopdefine boundariesconvert to binary data

    Advanced Composites Manufacturing Centre - University of Plymouth

  • Vf by optical microscopySEM images have low contrastsimilar chemistry of fibre and matrixTEM preparation difficultsample area too small for sensible statistical significance

    Advanced Composites Manufacturing Centre - University of Plymouth

  • Pro and con for microscopydata on fibre cross section size and shapedata on fibre clusteringcan be quantified by e.g. fractal dimensionlong preparation timesneed to distinguish at multiple scales

    Advanced Composites Manufacturing Centre - University of Plymouth

  • General references Grafil Test Methods (reference 000.05), Courtaulds Limited, Coventry, March 1980. PT Curtis, CRAG Test Methods for the Measurement of the Engineering Properties of Fibre Reinforced Plastics, Royal Aircraft Establishment Technical Report RAE-TR-88-012, February 1988. FJ Guild and J Summerscales, Microstructural image analysis applied to fibre composite materials: a review, Composites, 1993, 24(5), 383-394. J Summerscales (editor), Microstructural Characterisation of Fibre-Reinforced Composites, Woodhead Publishing, Cambridge, July 1998. ISBN 1-85573-240-8. CRC Press LLC, Boca Raton - Florida, July 1998. ISBN 0-8493-3882-4. AR Clarke and CN Eberhardt, Microscopy Techniques for Materials Science, Woodhead Publishing, Cambridge, July 1998. ISBN 1-85573-587-3. CRC Press LLC, Boca Raton - Florida, July 1998. ISBN 0-8493-1552-2.

    Advanced Composites Manufacturing Centre - University of Plymouth

  • To contact me Dr John SummerscalesSchool of Engineering: RYB 008University of PlymouthDevon PL4 8AA 01752.23.2650 01752.23.2638 jsummerscales@plymouth.ac.uk http://www.tech.plym.ac.uk/sme/jsinfo.htm

    Advanced Composites Manufacturing Centre - University of Plymouth