Abstract
Abstract In this paper we describe an investigation into the development of fibre orientation during melt extrusion through two convergent dies: a conical die and a slit die. The material used was a short glass fibre (aspect ratio = 24) reinforced polypropylene at two fibre weight fractions, 20% and 30%. The development of fibre orientation through the two convergent zones was measured in detail using sophisticated image analysis facilities developed in-house. It was found that the ‘pseudo-affine’ deformation model predicted the development of fibre orientation very well for both die configurations, in terms of the applied macroscopic elongational strains. The addition of a breaker plate placed in the barrel of the extruder, between the extruder screw and the convergent flow zones, was shown to produce the highest degree of fibre alignment in the extrudates, by introducing additional pre-orientation of the fibres. Mechanical measurements on the extrudates showed that for the very high degrees of fibre alignment attained, the bending modulus in the extrusion direction reached 90% of the theoretical maximum for the fibre aspect ratio used, and the crack resistance parallel to the preferred fibre direction remained high.
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More From: Composites Part A: Applied Science and Manufacturing
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