挤出成型GFRC板的纤维取向分布和轴拉性能

擠出成型工藝生產玻璃纖維增強水泥板 (GFRC)時 ,纖維在螺旋推擠力和速度剪力的作用下 ,大部分纖維能在擠出方向上形成定向排列 ,軸拉強度相對較高。而垂直于擠出方向的纖維分布相對較少 ,力學性能也相對較差。試驗結果表明 ,當纖維含量較低時 ,絕大部分纖維沿擠出方向分布 ,此時 ,平行擠出方向的軸拉強度遠大于垂直擠出方向。纖維摻量較高時 ,垂直擠出方向上的纖維分布量大大增加 ,相應的軸拉強度幾乎與平行擠出方向相等。此外 ,存在一個纖維摻量飽和點 ,超過此摻量 ,平行纖維方向的軸拉強度不再隨摻量的增加而提高 ,但有利于改善GFRC板的韌性和軸拉破壞形式 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 w ell know n 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 w hen 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 w hen 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.