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

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Accumulated sun hours [h] 1500 1000 500 Accumulated precipitation Weekly precipitation 0 0 10 15 20 25 30 35 40 45 Week nr. in 2001 Figure 6. Sun hours at the Årslev site in the growth period displayed as weekly sunshine and accumulated sun shine (data from Cappelsen, 2004). 5.2 Structure of hemp fibres The structural study is based on the middle section of hemp stems from the cultivar Felina that was cultivated at Danish Institute of Agricultural Sciences in 2001. 5.2.1 Structure on the plant stem level (0.002-10 MM) The hemp fibres are present in bundles as long as the stems, which can easily be peeled off the xylem surface by hand or machine (Figure 7). The fresh stem consists of a hollow cylinder of 1-5 mm thick xylem covered by 10-50 μm cambium, 100-300 μm cortex, 20- 100 μm epidermis and 2-5 μm cuticle (Garcia-Jaldon et al. 1998). The pith is empty space in dry stems. 18 Risø-PhD-11 200 150 100 50 Sun hours [h/week]
A B Figure 7. A: Model of transverse hemp stem section zooming to single fibres, secondary cell wall and finally the cell wall lamella. B: Model of the microfibril orientation throughout the secondary cell wall (Paper II).The S3 layer was not found in hemp fibres. 5.2.2 Structure on the fibre bundle level (1-100 μM) The cortex part of the hemp stems in Felina contains bundles of 100-300 polygonalshaped primary and secondary single fibres with 4 to 6 sides (Figure 7; Figure 9; Paper II). The single fibres are long (5-55 mm) compared with the fibres in the xylem (0.2-0.6 mm; Table 2; Vignon et al., 1995). The primary fibres nearest the stem surface are large (cell wall thickness = 7-13 μm; length = 20 mm; Sankari, 2000). These fibres are formed at the early growth stage during the phase of rapid stem elongation and contribute in Fedora, Felina and Futura to 92-95% of the bast fibres located in the cortex (Mcdougall et al., 1993; Sankari, 2000). The secondary fibres near the cambium layer are smaller (cell wall thickness = 3-6 μm; length = 2 mm; Sankari, 2000) and only present in the thick part of the stem (Mcdougall et al., 1993; Figure 9b). The average area of the transverse fibre section including cell lumen was calculated to 780 μm 2 ± 300 μm 2 and the lumen fraction in the fibres to 9% ± 7% (Paper II). The variation in area is due to actual variation in fibre size and not due to inaccurate measurement. Therefore the load carrying part of the single fibers is high (91%) compared with wood and straw fibres with larger lumens. Jute fibres and flax fibres have also small lumens (Cichocki and Thomason, 2002; Henriksson et al., 1997). Risø-PhD-11 19
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: Temperature [ o C] 35 30 25 20 15 1
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 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
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Kaar WE, Cool LG, Merriman MM, Brin
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Stowell EZ, Liu TS, 1961. On the Me
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Appendix A: Comprehensive composite
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The porosity constants can now be d
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Appendix D: Density and mechanical
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Paper I Changes in chemical composi
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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
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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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