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

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defibration of flax fibres (Henriksson et al., 1997) and was used to obtain hemp fibres for composite materials in Paper IV. 6.1.2 Yarn production The retted fibre bundles of 0.5-2 m length are traditionally used directly for production of yarn for rope production (Ole Magnus, Personal communication: telephone +45- 86994515). First hackling is done in two steps to straighten the fibres and remove short disordered fibres with a metal-pinned brush; this results in a sliver of parallel fibres useful for spinning. At industrial scale, the hackling is performed using metal-pinned brushes and rotating rollers to pull the fibres forward. This technique is basically also used to make sliver of shorter fibres like flax fibres (15-200 mm; Grosberg and Iype, 1999). By manual yarn spinning, some fibres from the sliver are mounted on a rotating hook. The fibres are stretched during the twisting process and more fibres are added, while the hand is moved backward to elongate the spun amount of yarn and keep a constant yarn thickness. At industrial scale, the stretching part of this process is called drafting. In drafting, the fibres become straightened by passing the sliver through a series of rollers with increasing rotational speed in the forward direction (Figure 18-left). The drafting process elongates the thick sections of the filament so they get the same thickness as the thinner sections, resulting in a uniform sliver ready for spinning (Figure 18-centre; Madsen, 2004). The most common spinning method is ring spinning, in which slivers delivered from the drafting rollers become twisted by the traveller that is freely rotating on a ring (Madsen, 2004). The ring distributes the yarn onto a rotating bobbin. Each traveller rotation introduces one twist. Increased delivering speed from the drafting rollers decreases the number of twists per length. The twisting forces the fibres to take a helical structure and results in inherent sliding friction between the fibres (Madsen, 2004) and in axial strength in the yarn (Grosberg and Iype, 1999). The produced yarn can be wound on a metal frame (Figure 18-right) to get aligned fibre assemblies, ready for composite production (Madsen and Lilholt, 2003). 32 Risø-PhD-11
Figure 18. From fibre filament to aligned fibre assemblies: The drafting process with three pairs of rollers at different rotation speed (v; left), followed by ring spinning to get yarn (Grosberg and Iype, 1999; centre) and filament winding of yarn to get aligned fibre assemblies (Modified from Madsen, 2004; right). 6.2 From fibre assemblies to composite materials 6.2.1 Fibre part Composite materials can be reinforced with non-woven fibre mats, with woven yarn and with wound yarn. Plant fibres from different origins are useful as reinforcement. These fibres originate from leaves (sisal, pineapple and henequen), from bast (flax, hemp, ramie, jute, kenaf), from seed (cotton) and from fruits (coconut husk) (Mohanty et al., 2000; Table 2; Table 3). Risø-PhD-11 33
Page 1 and 2: Risø-PhD-11(EN) Properties of hemp
Page 3 and 4: Contents Preface 6 1 Resumé 7 2 Li
Page 5 and 6: 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: fibre mats, which are made by air-d
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 and 58: Thereby, the effective fibre streng
Page 59 and 60: a b Composite tensile strength σcu
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
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Page 89 and 90:
Paper II Hemp fiber microstructure
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ABSTRACT Characterization of hemp f
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METHODS AND TECHNIQUES Treatment of
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2000) and their orientation gave th
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By TEM microscopy, the single fiber
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Table 1. Chemical composition of th
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Table 2. Tensile strength (σ) and
Page 103 and 104:
Morvan, C., Jauneau, A., Flaman, A.
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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
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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
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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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