Properties of hemp fibre polymer composites -An optimisation of ...
Properties of hemp fibre polymer composites -An optimisation of ...
Properties of hemp fibre polymer composites -An optimisation of ...
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water vapour and air are removed from the <strong>fibre</strong>s so the molten <strong>polymer</strong> can impregnate<br />
them. Pressure consolidation (1 MPa) is used to improve the penetration <strong>of</strong> the <strong>fibre</strong> lay<br />
up and to increase the <strong>fibre</strong> compaction (Figure 22b; <strong>An</strong>dersen and Lilholt, 1999). Since<br />
the <strong>fibre</strong>s will slide between each other during the compression, the obtainable <strong>fibre</strong><br />
volume fraction in the final composite increases versus the consolidation pressure<br />
(Madsen and Lilholt, 2002).<br />
6.2.4 Composite preparation in this study<br />
The <strong>composites</strong> reinforced with aligned <strong>fibre</strong>s that were made in this study were<br />
fabricated with epoxy as matrix material (Paper IV). Epoxy was used since this low<br />
viscosity <strong>polymer</strong> penetrates easily into the <strong>fibre</strong> assembly and forms covalent binding to<br />
the plant <strong>fibre</strong>s resulting in strong interface (Obrien and Hartman, 1971). It was not<br />
suitable to make the <strong>composites</strong> in vacuum because <strong>of</strong> evaporation <strong>of</strong> chemicals from the<br />
fluid epoxy, which results in holes in the produced <strong>composites</strong> (Stephanie Feih, Personal<br />
communication: telephone +61-3-96769904). The <strong>composites</strong> were made with pressure<br />
consolidation using manually tightened clamps in a normal oven during pre-curing at<br />
40°C and curing at 120°C (Figure 23; Figure 21-bottom).<br />
Risø-PhD-11 37
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