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

a: Tensile strength (σ uf) for n=2.1
Fibre strength [MPa]
800
600
400
200
0
b: Stiffness (Ef) for n=1
Fibre stiffness [GPa]
120
100
80
60
40
20
0
0 2 4 6 8
Porosity [% v/v]
0 2 4 6
Porosity [% v/v]
8
Raw hemp bast treated with:
Raw bast Water retting C.sub. P.rad. Hemp yarn
Figure 36. Tensile strength (a) and stiffness (b) calculated for the fibres versus
composite porosity with nσ = 2.1 and nE=1. The markers and black regression lines
represent results not corrected for porosity and the grey regression lines represent the
results with correction of the composite properties for porosity (unpublished data).
Based on the determined factors for consideration of porosity, the effect of porosity on
composite strength and fibre strength could be determined with a model. The result of
the model shows a decrease in effective fibre strength from 700 to 560 MPa by an
increase in porosity from 0 to 10% v/v (Figure 37a). The decrease in effective fibre
strength and composite strength were thereby both 20%. The effective fibre stiffness
decreased from 100 to 90 GPa by the increase in porosity from 0 to 10% v/v (Figure
37a). The decrease in effective fibre stiffness and composite stiffness were both 10%.
56 Risø-PhD-11
10
10