FIBER ALIGNMENT AND PROPERTY DIRECTION DEPENDENCY OF GFRC EXTRUDATE

This paper presents the results of experimental studies on fiber alignment and its influence on the tensile strength along different directions for fiber reinforced cement fabricated by extrusion technique. It is well known that fibers can be aligned into the desired directions during an extrusion process through a properly designed die and high shear. The fiber alignment, of course, would lead to direction dependency of the tensile properties of GFRC extrudate. The current study investigated such a dependency using the existing extrusion equipment. It is found that when the fiber volume ratio is low, say 1 % of glass fiber, it can be aligned almost in unified direction, i.e. extrusion direction. As a result, the tensile strength of a thin plate along the extrusion direction is much higher than that of along the transverse direction. When the fiber volume ratio is increased to 2 % or 4 %, the fiber volume along the transverse direction is largely increased even though the majority of fiber is still aligned along the extrusion direction. Thus, the tensile strength in the transverse direction is significantly increased. In fact, the tensile strength along the transverse direction is almost the same to that along the extrusion direction when the fiber volume ratio reaches 2 %. Furthermore, the extrusion direction strength of samples did not increase proportionally to the fiber volume ratio. But the toughness and the destroy form have been improved with the fiber volume ratio increasing.