Effect of pyrrole-conjugated structure on the thermal cycle stability of carbon fiber reinforced resin-based composites
Objective Carbon fiber(CF)reinforced resin matrix composites(CFRPs)have attracted much research attention in due to their good overall performance.However,CFRPs suffer from the problems of weak interfacial bonding between carbon fibers and matrix,and the mismatch of thermal expansion coefficients of the two phase materials brings about interfacial damage during thermal cycling.Existing interfacial modification techniques are difficult to solve the above two problems,and therefore a new solution is proposed in this paper.Method Optimization of interfacial properties of composites was carried out based on structural adjustment of polypyrrole(PPy)to achieve surface modification by polymerizing a layer of PPy on carbon fiber.The PPy layer with more conjugated structure was obtained by adjusting different polymerization temperature.The interfacial bonding property,thermal expansion property and thermal cycling stability of CFRPs prepared under different polymerization conditions were studied.Results The results showed that the surface roughness of PPy/CF-0 fibers polymerized at 0 ℃ was higher than that of CF by a factor of 2.09,which was conducive to the anchoring of the epoxy resin on the surface of carbon fibers.Moreover,the PPy on the surface of PPy/CF-0 fibers showed a higher α-α conjugate structure,which led to the negative coefficient of thermal expansion of the composites,and increased the interlayer shear strength and interfacial shear strength of the composites by a maximum of 60 MPa and 47.5 MPa,respectively.The PPy/CF-0 fiber composites also demonstrated excellent thermal cycling stability,and the shear strength was still maintained at more than 70％of the initial value after 100 thermal cycling tests.Conclusion Compared with unmodified CF,the interlaminar shear strength(ILSS)and interfacial shear strength(IFSS)of PPy/CF-0 fiber-reinforced composites modified by PPy coating reached 88.9 MPa and 65.4 MPa,respectively,which were 1.56 and 1.70 times higher compared with CF,and the shear strength was maintained at more than 70％of the initial value after thermal cycling up to 100 times.The polymerization temperature has a significant effect on the morphology,structure and properties of the PPy layer.Through AFM observation and FT-IR spectra analysis,the surface of PPy/CF-0 fibers prepared by low-temperature polymerization at 0 ℃ has a large roughness and the content of α-α conjugated structure of PPy is as high as 74％.The PPy/CF-0 fiber and its reinforced composites showed negative coefficient of thermal expansion.The PPy-modification technology provides a new way of thinking for the design of composite materials by changing the surface roughness and negative thermal expansion coefficient,thus effectively enhancing the interfacial bonding performance and improving the thermal cycling stability of fiber-reinforced composites.
万方数据
维普
