Study on compressive strength and thermal conductivity of interlayer reinforced and stiffened CFRP composites with CNT films
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摘要: 近年来结构功能一体化碳纤维增强树脂基复合材料(CFRP)受到广泛关注,而高强、高模和高导热的碳纳米管膜的层间增强增刚技术为此提供了新思路。本文基于原始的碳纳米管膜(P-CNTF),采用湿拉伸法和环氧化反应制备了取向、环氧化和取向-环氧化碳纳米管膜(S-CNTF、E-CNTF和S-E-CNTF),分别用于层间增强增刚CFRP (分别记作CFRP/S-CNTF、CFRP/E-CNTF和CFRP/S-E-CNTF),分析了碳纳米管膜的物化特性和拉伸性能,并结合Jumahat的联合预测模型和实验验证研究了碳纳米管膜对CFRP的纵向压缩强度和失效机制的影响,同时探讨了CFRP的面内导热性能及其导热机制。结果表明:相较P-CNTF,S-E-CNTF膜内碳管呈现高度取向的集束状态,表面化学活性明显增强,使其拉伸强度和模量分别提高到116 MPa和6.3 GPa。对比于CFRP,CFRP/S-E-CNTF的面内剪切模量和层间剪切强度分别提高了28.3%和34.2%,表明S-E-CNTF能有效增强CFRP抵抗剪切变形和裂纹扩展的能力;模型预测表明CFRP/S-E-CNTF的理论弹性压缩应力和塑性压缩应力分别提高了30.7%和32.3%,并且与实验结果吻合较好;同时基于S-E-CNTF在CFRP层间区域构建的三维导热网络,CFRP/S-E-CNTF的面内导热系数提高到了7.8 W/(m·K)。Abstract: In recent years, the structure-function integrated carbon fiber reinforced plastic (CFRP) composites have attracted extensive attention, and the interlayer reinforcing and stiffening based on carbon nanotube (CNT) films with high strength, high modulus and high thermal conductivity provided an innovative idea. In this paper, the stretched CNT films (S-CNTF), epoxided CNT films (E-CNTF) and stretched-epoxided CNT films (S-E-CNTF) were prepared by wet stretching and epoxidation reaction based on pristine CNT films (P-CNTF), and used for interlayer reinforcing and stiffening CFRP composites (CFRP/S-CNTF, CFRP/E-CNTF and CFRP/S-E-CNTF), respectively. The physicochemical characteristics and tensile properties of CNT films were analyzed, and the effects of S-E-CNTF on longitudinal compressive strength and failure mechanism of composites were studied by combining Jumahat's combined model and experimental verification. Meanwhile, the in-plane thermal conductivity and corresponding mechanism of composites were discussed. In contrast with P-CNTF, the CNTs in S-E-CNTF present highly oriented bunching morphology and the surface chemical activity of S-E-CNTF is observably improved, so that the tensile strength and modulus of S-E-CNTF are enhanced to 116 MPa and 6.3 GPa, respectively. In comparison with CFRP, the in-plane shear modulus and interlaminar shear strength of CFRP/S-E-CNTF are increased by 28.3% and 34.2%, respectively, implying that the S-E-CNTF can effectively inhibit delamination and enhance resistance of shear deformation of CFRP. The model prediction also shows that the theoretically elastic and plastic compressive stress of CFRP/S-E-CNTF are increased by 30.7% and 32.3%, respectively, which is in accord with experimental values. Meanwhile, based on the three-dimensional thermal conductivity network constructed by S-E-CNTF in the interlaminar region of CFRP, the in-plane thermal conductivity of CFRP/S-E-CNTF is improved to 7.8 W/(m·K).
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图 12 CFRP、CFRP/P-CNTF、CFRP/S-CNTF、CFRP/E-CNTF和 CFRP/S-E-CNTF复合材料纵向压缩强度预测和实验值
σelastic—Compressive stress at the elastic stage; σplastic—Compressive stress at the plastic stage
Figure 12. Predicted and experimental value of longitudinal compressive strength of CFRP, CFRP/P-CNTF, CFRP/S-CNTF, CFRP/E-CNTF and CFRP/S-E-CNTF composites
图 15 CFRP、CFRP/P-CNTF、CFRP/S-CNTF、CFRP/E-CNTF和 CFRP/S-E-CNTF复合材料的热红外图像(a)、温度-加热时间曲线图(b)、面内热扩散系数(c)和面内导热系数(d)
Figure 15. Thermal infrared images (a), temperature-heating time curves (b), in-plane thermal diffusivity (c) and in-plane thermal conductivity (d) of CFRP, CFRP/P-CNTF, CFRP/S-CNTF, CFRP/E-CNTF and CFRP/S-E-CNTF composites
表 1 P-CNTF、S-CNTF、E-CNTF 和 S-E-CNTF的碳、氧原子和环氧基团的摩尔含量
Table 1. Molar content of carbon, oxygen and epoxy groups of P-CNTF, S-CNTF, E-CNTF and S-E-CNTF
Sample C/mol% O/mol% Epoxides/mol% P-CNTF 96.8 3.2 2.2 S-CNTF 96.3 3.7 2.8 E-CNTF 85.2 14.8 13.3 S-E-CNTF 87.3 12.7 12.2 -
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