The phenomenon of fibre alignment during the extrusion process was studied. Fibre alignment largely depends on die shape and compression, as well as the shear force generated in the extruder. Fibre alignment orientation, of course, would lead to direction dependency of the tensile properties of fibre-reinforced cement (FRC) extrudates. Such a dependency was studied. It was found that, when fibre volume ratio is small, say 1% glass fibre, most of the fibre can be aligned in the extrusion direction. As a result, the tensile strength of the thin plate along the extrusion direction is much higher than that along the transverse direction. When the total fibre volume ratio is increased to 2% or 4%, the fibre volume along the transverse direction is largely increased although the percentage of the fibre aligned along the extrusion direction is still higher. Thus, the tensile strength at a transverse direction can be significantly enhanced. In fact, the tensile strength of the samples along the transverse direction is almost the same as that along the extrusion direction when the fibre volume ratio reaches 2%. Furthermore, the strength of the sample at the extrusion direction does not increase proportionally to the fibre volume ratio. For comparison, plain sheets without any fibres were prepared by both casting and extrusion. Mechanical properties of the sheets were also tested, and the results show that the extrusion process and fibre addition do enhance the tensile properties. A polymer coating on the surface of the samples was also used to improve the tensile properties of the extrudates with low fibre volume ratio, which shows some promising results. 11 refs.
Primary author(s): Qian X; Zhou X; Mu B; Li Z
Zhejiang,University; Hong Kong,University of Science & Technology