Properties of hemp fibre polymer composites -An optimisation of ...

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aw hemp bast, water retted hemp or P. radiata Cel 26 defibrated hemp, as reinforcement was 20 GPa, 26 GPa and 30 GPa, respectively without consideration of porosity (Ec). Cultivation of P. radiata Cel 26 for defibration of hemp fibres resulted thereby both in the highest composite strength and highest composite stiffness. Based on obtainable composite strength and stiffness, the best defibration method was cultivation of P. radiata Cel 26 followed by water retting and at last by cultivation of C. subvermispora. It was determined that the hemp fibres tensile strength and stiffness were affected by the investigated defibration methods at 90% probability using analysis of variance (F-test with number of samples = 4 and number of repetitions = 23 for F0.1) (Paper IV). The curve for composite strength for E-glass fibres had about twice the slope of the curves for hemp yarn and defibrated hemp fibres. That is due to the high strength of glass fibres (1200 – 1500 MPa) compared with hemp fibres (535 – 677 MPa). The composites reinforced with glass fibres with a maximum strength of 770 MPa could get much stronger than the hemp fibre reinforced composites (230 MPa) due to the higher obtainable fibre content. The curve for composite stiffness for E-glass fibres had similar slope to the curve for raw hemp bast. That is due to the moderate stiffness of glass fibres (71 – 77 GPa) compared with the defibrated hemp fibres (88 – 94 GPa). The composites reinforced with glass fibres had a maximum stiffness of 40 GPa, which is not much higher than obtained with hemp fibres (30 GPa). The curve for composite strength for barley straw had about four times lower slope than the curves for defibrated hemp fibres. That is due to the low strength of barley straw (240 MPa) compared with the hemp fibres (535-677 MPa) and the higher porosity content. The composites reinforced with barley straw with a maximum strength of 19 MPa were up to 10 times weaker than the hemp fibre reinforced composites (230 MPa) due to the low obtainable fibre content and the very high porosity content (up to 44% v/v). The curve for composite stiffness had 15 times lower slope than the curves for the hemp based fibres. That is due to the low fibre stiffness (22 GPa) and high porosity content. The composites were therefore not much stiffer than the epoxy matrix (3 GPa). 58 Risø-PhD-11
a b Composite tensile strength σcup [MPa] Composite stiffness Ecp [GPa] 40 30 20 10 600 400 200 0 0 E-glass Hemp yarn P.rad. tr. hemp Water retted hemp Raw bast Barley straw 0 10 20 30 Fibre content [% v/v] P.rad. tr. hemp Water retted hemp E-glass Raw bast Hemp yarn Barley straw 0 10 20 30 40 Fibre content [% v/v] Figure 38. Tensile strength and stiffness for the composites corrected for porosity versus fibre content (Paper IV+unpublished data). Risø-PhD-11 59 40
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Risø-PhD-11(EN) Properties of hemp
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Contents Preface 6 1 Resumé 7 2 Li
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PhD thesis: Properties of hemp fibr
Page 7 and 8: 1 Resumé Karakterisering af hampef
Page 9 and 10: 2.4 Oral presentations Anders Thyge
Page 11 and 12: 4 Introduction Hemp (Cannabis sativ
Page 13 and 14: 4.2 The outline of the thesis The f
Page 15 and 16: The only fertilizer used was 360/48
Page 17 and 18: Temperature [ o C] 35 30 25 20 15 1
Page 19 and 20: A B Figure 7. A: Model of transvers
Page 21 and 22: Figure 8. Lignin (a), pectin (b) an
Page 23 and 24: Figure 11. Microfibril angles (MFA)
Page 25 and 26: Teleman, 1997). The crystal structu
Page 27 and 28: to the computing effort and the sub
Page 29 and 30: Figure 15. The structure of hemicel
Page 31 and 32: fibre mats, which are made by air-d
Page 33 and 34: Figure 18. From fibre filament to a
Page 35 and 36: A B C D Figure 20. Chemical structu
Page 37 and 38: water vapour and air are removed fr
Page 39 and 40: 7 Defibration methods Defibration m
Page 41 and 42: Table 5. Fibre yield and cellulose
Page 43 and 44: a b c Composition [% w/w] 100 Compo
Page 45 and 46: 8 Fibre strength in hemp The streng
Page 47 and 48: 8.2 Effect of pre-treatment of hemp
Page 49 and 50: E-modulus [GPa] 90 80 70 60 50 40 3
Page 51 and 52: Second mode: Failure is controlled
Page 53 and 54: structure, which made much higher f
Page 55 and 56: Table 7. Porosity factors determine
Page 57: Thereby, the effective fibre streng
Page 61 and 62: Table 9. Mechanical properties in a
Page 63 and 64: a σ c/ρ c [10 3 m 2 /s 2 ] b Ec/
Page 65 and 66: Fibre strength σ f [MPa] Fibre sti
Page 67 and 68: 11 References Andersen TL, Lilholt
Page 69 and 70: Kaar WE, Cool LG, Merriman MM, Brin
Page 71 and 72: Stowell EZ, Liu TS, 1961. On the Me
Page 73 and 74: Appendix A: Comprehensive composite
Page 75 and 76: The porosity constants can now be d
Page 77 and 78: Appendix D: Density and mechanical
Page 79 and 80: Paper I Changes in chemical composi
Page 81 and 82: Risø-PhD-11 81
Page 89 and 90: Paper II Hemp fiber microstructure
Page 91 and 92: ABSTRACT Characterization of hemp f
Page 93 and 94: METHODS AND TECHNIQUES Treatment of
Page 95 and 96: 2000) and their orientation gave th
Page 97 and 98: By TEM microscopy, the single fiber
Page 99 and 100: Table 1. Chemical composition of th
Page 101 and 102: Table 2. Tensile strength (σ) and
Page 103 and 104: Morvan, C., Jauneau, A., Flaman, A.
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Risø-PhD-11 109
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Risø-PhD-11 111
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Risø-PhD-11 113
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Risø-PhD-11 117
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Paper IV Comparison of composites m
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ABSTRACT Aligned epoxy-matrix compo
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the calculation of volume fractions
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solution (pH 4) for 4 h at 85°C. L
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E ⎛ dσ c ⎞ = ⎜ ⎟ ⎝ dε
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Table 2. Chemical composition, stru
Page 131 and 132:
transverse section of the small hem
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Long fibres that pass through the e
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Figure 6. Effect of composite fabri
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DISCUSSION The defibration of hemp
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This investigation showed that the
Page 141 and 142:
Bos, H.L., Molenveld, K., Teunissen
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Thygesen, A., 2006. Properties of h
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Risø-PhD-11 145
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Risø’s research is aimed at solv
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