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

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Figure 19. Pathway used to make composite materials of fibre mats and of aligned fibre assemblies with thermoplastics or with thermosets. 6.2.2 Matrix part The matrix part of composite materials can both be thermoplastic like polyethyleneterephtalate (PET), polypropylene (PP) and polyamide (nylon) and thermoset, like epoxy and polyester (Figure 19; Figure 20). Thermoplastic has the advantage of giving greater fracture toughness, larger elongation at fracture, faster and more automatic processing, unlimited shelf life of raw material, recycling and a cleaner working environment (Lystrup, 1997). Thermoset impregnated composite materials have the advantage of being processed at lower temperatures (40-120°C) compared with polypropylene at 200°C, since the thermal damage of the fibres is reduced at the lower temperature (Madsen, 2004; Figure 19-left; Figure 21-bottom). The polymer viscosity is low in thermosets (0.1-10 Pa·s; Lystrup, 1997) compared with thermoplastics (100-1000 Pa·s; Brüning and Disselbeck, 1992). However, the viscosity can be controlled during pressing within a wide range, since it decreases with increasing temperature. 34 Risø-PhD-11
A B C D Figure 20. Chemical structure of (A) PE (polyethylene), (B) PP (polypropylene), (C) PET (polyethyleneterephtalate) and (D) epoxy (diglycidyl ether of bisphenol A) (Muzzy, 2000). 6.2.3 Composite processing Composites can be made with fibres as mats and as aligned assemblies impregnated with matrix polymer (Figure 19-left and Figure 21-top). The processing techniques used are autoclave consolidation and mechanical press consolidation (Figure 22). Autoclave consolidation is performed in vacuum to evaporate water and remove air from the fibres placed in vacuum backs (Figure 22a). The fibres and the fluid thermoset polymer are press consolidated during the curing process using pressurized air to compact the fibres. Risø-PhD-11 35
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: Figure 18. From fibre filament to a
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
Page 95 and 96:
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
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
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the calculation of volume fractions
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solution (pH 4) for 4 h at 85°C. L
Page 127 and 128:
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
Page 145 and 146:
Risø-PhD-11 145
Page 147:
Risø’s research is aimed at solv
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