挤出成型GFRC板的纤维取向分布和轴拉性能

FIBER ALIGNMENT AND PROPERTY DIRECTION DEPENDENCY OF GFRC EXTRUDATE

挤出成型工艺生产玻璃纤维增强水泥板 (GFRC)时 ,纤维在螺旋推挤力和速度剪力的作用下 ,大部分纤维能在挤出方向上形成定向排列 ,轴拉强度相对较高。而垂直于挤出方向的纤维分布相对较少 ,力学性能也相对较差。试验结果表明 ,当纤维含量较低时 ,绝大部分纤维沿挤出方向分布 ,此时 ,平行挤出方向的轴拉强度远大于垂直挤出方向。纤维掺量较高时 ,垂直挤出方向上的纤维分布量大大增加 ,相应的轴拉强度几乎与平行挤出方向相等。此外 ,存在一个纤维掺量饱和点 ,超过此掺量 ,平行纤维方向的轴拉强度不再随掺量的增加而提高 。

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.