K49 and F-Ⅲ two kinds of different structure aramid fibers and their 5224A epoxy matrix composites were selected. The tension strength of single fiber, FTIR, XPS, DSC, SEM, mechanical and dielectrical properties was used to characterize the physicochemical properties of fibers and structure/wave-transmitting properties of composites. It is found that different fibers result in different changes under the same solar radiation condition. The obvious "self-shield" phenomenon is observed in K49 fibers, but there's no proof that F-Ⅲ has the same ability. A tension strength conservation rate of 82% is obtained after 400 hours solar radiation. F-Ⅲ fibers, by contrast, are sensitive to solar radiation and a conservation rate of 50% is obtained at the same condition. The decreased tension strength is due to physicochemical degradation on the surface of the fibers and the decrease of crystallinity degree. It is proved that solar radiation has no obvious effect on the properties of composites. The flexibility, ILSS and dielectric properties has little change. The tensile strength is slightly improved, and the compression strength is slightly decreased. A decrease of 11.8% is obse-rved on K49/5224A composites and 6.6% for that of F-Ⅲ/5224A. It is because of that the degrad-ation occurred on the surface of composites.
Mixed C—N stretching and N—H bending vibrations，aramid absorption band Ⅲ
Combination of N—H deformation and C—N stretching vibrations，aramid absorption band Ⅱ
C—H in-plane deformation of benzene ring
C—C stretching vibration of benzene ring
1, 4-disubstituded, C—H wagging of benzene ring
C—H in-plane bending deformation of benzene ring
Table 2 芳纶纤维特征官能团红外吸收峰位置
Area fraction of C—C/% (284.7±0.1)eV
Area fraction of —C—N— & —C—O—/% (286.4±0.1)eV
Area fraction of —C＝O/% (288.6±0.1)eV
Area fraction of —O—C＝O/% (289.0±0.1)eV
Table 3 芳纶纤维表面官能团信息
Endothermic peak area/(J·g-1)
Content rate of peak area/%
Table 4 DSC曲线特性参数
Fig.4 K49纤维辐照前后的SEM照片(a)0h;(b), (c)400h
Fig.5 F-Ⅲ纤维太阳辐照前后的SEM照片 (a)0h;(b), (c)400h
Table 5 复合材料的力学性能
Fig.6 复合材料太阳辐照老化前后的SEM照片 (a)辐照前; (b)辐照后
Table 6 复合材料的常温介电性能
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