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本文采用下垂法原理测定玻璃纤维、碳纤维、Kevlar-49、国产芳纶和碳化硅纤维丝束的热膨胀系数,作出了纤维轴向热膨胀-温度曲线图。结果表明,玻璃纤维和碳化硅纤维在400℃以下时膨胀系数均为正值。碳纤维在250℃以下其长度随温度的升高而缩短,按微分定义的热膨胀系数为负值;在250℃以上变为长度随温度升高而伸长,按微分定义的热膨胀系数为正值;但一直到400℃,其平均热膨胀系数仍为负值。Kevlar-49在80～300℃区间内受热收缩,按微分定义的热膨胀系数为负值;此温度区间以外受热膨胀,按微分定义的热膨胀系数为正值;其平均热膨胀系数在1000℃以下为正值,超过100℃为负值。国产芳纶从室温到400℃两种定义的热膨胀系数均为负值。
In this paper, the thermal expansion coefficient of fiberglass, carbon fiber, Kevlar-49, domestic aramid fiber and silicon carbide fiber tow was measured by the sagging principle, and the fiber axial thermal expansion-temperature curve was made. The results show that the expansion coefficients of glass fiber and silicon carbide fiber are both positive at 400 ℃. The carbon fiber shortens its length with the increase of the temperature below 250 ° C, and the coefficient of thermal expansion defined by the differential is negative. When the temperature is above 250 ° C, the length becomes longer with increasing temperature, and the coefficient of thermal expansion defined by the differential is a positive value. But until 400 ℃, its average coefficient of thermal expansion is still negative. Kevlar-49 heat shrinks in the temperature range of 80-300 ° C, and the coefficient of thermal expansion defined by differential is negative. The thermal expansion coefficient outside this temperature range is positive, and the coefficient of thermal expansion defined by differential is positive. The average coefficient of thermal expansion below 1000 ° C is positive Value, more than 100 ℃ is negative. Domestic aramid from the room temperature to 400 ℃ two kinds of definitions of the thermal expansion coefficient is negative.