单向纤维增强环氧复合材料的热膨胀系数

THERMAL EXPANSION COEFFICIENTS OF UNIAXIAL FIBER REINFORCED EPOXY COMPOSITES

本文在123—413K的温度范围内,测量了单向玻璃纤维和碳纤维增强环氧树脂复合材料α_P^C(纤维方向),α_(T1)~C(横截面板厚度方向),α_(T2)~2(横截面板宽度方向)三个热膨胀系数.研究了纤维体积分数V_f和纤维表面处理对α_P^C和α_T^C的影响.结果表明,α_P^C在整个温度范围内不受纤维表面处理影响,随V_f的增加而减小,变化规律符合Schapery方程.对于横向热膨胀系数,在T<基体玻璃化温度T_g^m时,有α_(T1)~C α_(T2)~C=α_(T)~C,在V_f 0.3时,有α_T^C>α_m(基体的),而后随V_f的增加而减小,经分析也符合Schapery理论.在T>T_g^m时,α_(T1)~C和α_(T2)~C呈各向异性,特别在纤维表面未处理时更为显著.形态研究表明,其原因是在纤维铺层之间存在片状树脂层.

In the present paper the effects of the fiber content and the interface on the linear thermal expansion coefficient of the uniaxial glass fiber and the carbon fiber reinforced epoxy composites have been studied in the temperature range from 123 to 415K. The results show that the transverse thermal expansioncoefficient of the composites are greater than that of the matrix itself when the fiber content Vf = 0.2 to 0.4 and the surface treatment seems to have no effect on the axial thermal expansion coefficient of the composites. The relationships between the fiber content and the axial thermal expansion coefficient can be described by Shapery's equation. When the temperature is higher than the glass transition temperature of the epoxy matrix, the two transverse direction (X-and Y-axis) thermal expansion coefficients are quite different from those expected by Shapery's equation. The morphology shows that an epoxy resin layer existed between the laminas. The thickness of the resin layer depends on the surface treatment of the fibers, hence it make the difference between the two thermal expansion coefficients in the two transverse direction.