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

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Roughly 20% lower fibre strength was determined by fibre bundle test than by single fibre test of the raw felina hemp fibres combined with 60% lower standard deviation. The lower strength and standard deviation in the fibre bundle tests are presumably due to the bundle effect as explained with the Weibull distribution (Sankari, 2000). Fibre bundle strength [MPa] 2000 1500 1000 500 0 Raw hemp Water retted hemp C.sub. tr. hemp P.rad. tr. hemp Hemp yarn Barley straw Treatment of Felina hemp Figure 30. Fibre bundle strength of retted and fungal defibrated hemp fibres, compared with traditionally produced hemp yarn and barley straw (Paper IV). 8.3 Effect of microfibril angle and twisting angle Studies of stiffness in wood fibres with different microfibril angles (Page et al., 1977) and studies of stiffness in composites with varied fibre angle to the test direction (Madsen, 2004) have shown decreasing stiffness versus the angle. This decreasing trend is illustrated in Figure 31. Based on the microfibril angle throughout the fibre wall in hemp fibres, which varies concentrically, the cell wall stiffness when pulling in fibre axis direction is lowest in the S1 layer with microfibrils running perpendicular to the fibre axis. The microfibrils are almost parallel with the fibre axis in the inner 70-90% of the S2 layer (Davies and Bruce, 1997), which results in high stiffness. The difference in stiffness throughout the fibre wall will result in different stress concentrations during tensile test. That might explain the cracks that were observed between the concentric layers in the fractured fibres after fibre bundle tests (Paper II). 48 Risø-PhD-11
E-modulus [GPa] 90 80 70 60 50 40 30 20 10 0 0 20 40 60 80 Microfibril/Yarn - angle [degrees] PET-hemp yarn composite Wood pulp single fibres Figure 31. Comparison of reinforcing orientation on the single fibre level and the composite level: Relationship between wood fibre stiffness and microfibril angle in the S2 layer (Page et al., 1977). Stiffness of PET-hemp yarn composites with the yarn axis inclined at different angles to the test direction (Madsen, 2004). The uncertainty is determined as standard deviation on the calculated E-modulus shown as bars. Risø-PhD-11 49
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 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: 8.2 Effect of pre-treatment of hemp
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
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-11 105
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Paper IV Comparison of composites m
Page 121 and 122:
ABSTRACT Aligned epoxy-matrix compo
Page 123 and 124:
the calculation of volume fractions
Page 125 and 126:
solution (pH 4) for 4 h at 85°C. L
Page 127 and 128:
E ⎛ dσ c ⎞ = ⎜ ⎟ ⎝ dε
Page 129 and 130:
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
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Bos, H.L., Molenveld, K., Teunissen
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Thygesen, A., 2006. Properties of h
Page 145 and 146:
Risø-PhD-11 145
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Risø’s research is aimed at solv
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