杉木纖維添加量對水泥複合材物理機械性質之影響

Effect of wood (Cunninghamia lanceolata) fiber content on the physical and mechanical properties of the cement composites

本研究利用惠蓀林場杉木（Cunninghamia lanceolata）作為纖維原料，與水泥砂漿拌合製備對環境友善的水泥複合材（Wood/cement composite, WCC），以探討木纖維添加量對水泥複合材物理機械性質之影響。有關物理性質方面，試驗結果得知WCC密度隨木纖維添加量增加而減少，但其乾燥收縮率反而增加。另外，由抗拉、抗彎及抗壓強度試驗結果觀察發現，與未添加纖維的WCC相比，添加木纖維的WCC具有較低的機械性質，且隨著纖維添加量增加而有降低的趨勢現象。其主要原因推測係因添加木纖維造成水泥基質的孔隙及纖維團聚所致。然而，高木纖維添加量之WCC之載重－位移曲線出現應變軟化，此表示由脆性材料轉為準脆性材料。而對WCC於極限載重下的應變， 則隨著木纖維添加量增加而增加，此結果顯示木纖維的添加使WCC極限應變增加。另一方面，由抗壓強度試驗結果可知，WCC之壓縮強度與密度間具有高度指數增長的相關性。此外，WCC之壓縮破壞型態，則隨木纖維添加量增加，從縱向劈裂破壞轉變為剪切破壞。

In this study, China fir (Cunninghamia lanceolata) fibers obtained from Huisun Experimental Forest Station was used as raw materials to manufacture the environmental friendly wood/cement composite (WCC) to evaluate the effect of wood fiber content on the physical and mechanical properties of the WCCs. In physical properties, the results exhibited that, while the apparent density of the WCC decreased with increasing wood fiber content, the drying shrinkage increased. In addition, the WCC had lower mechanical strengths compared to the pure cement and a tendency to decrease with increasing fiber content. This phenomenon is related to fiber aggregate and pores resulted from the addition of wood fibers in the cement matrix. The force-stroke curve of the WCC with high wood fiber content showed strain softening, indicating that the WCC became a quasi-brittle material. However, the strain of the WCC under the ultimate load increased with increasing wood fiber, suggesting that the addition of wood fiber increased the strain under the ultimate load. On the other hand, compressive strength and density of the WCC was correlated exponentially. Furthermore, with increasing fiber content, the compressive failure mode of the WCC changed from longitudinal splitting failure to shear failure.