8 May 1995 Anisotropy of conductivity in carbon fiber-reinforced plastics with continuous fibers
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Abstract
Carbon fiber-reinforced plastics (CFRP), as high strength advanced materials are often used as media for embedding sensors and actuators. Due to the properties of components and processing conditions they are electrically anisotropic, with coefficient of anisotropy sometimes exceeding several thousands. This may prevent elimination of static electricity and cause erosion of material due to micro discharges at contacts with fastenings and embedded sensors and actuators, causing their malfunction. For this reason, the investigation of electrical properties of CFRP may provide the solution to this problem. Distribution of electric current field in CFRP and related with it possible errors in measurements of longitudinal conductivity and anisotropy are analyzed. CFRP have been prepared from PAN or cellulose fibers with different heat treatment temperatures and conductivity anisotropy was measured as a function of filler volume fraction and processing conditions. With increasing loading coefficient of anisotropy (alpha) decreases. Lower values of (alpha) were observed when curing agents containing ionic complexes of metals were used. Modifications of fiber surface with hydrophobic agents results in increased anisotropy. Composites prepared with carbon fabrics are isotropic in the fabric plane. Coefficient of anisotropy decreases with increasing molding pressure and depends on the type of weaving of fabric. In hybrid composites with alternating layers of carbon fabric and complex fiber fabric anisotropy is higher due to partial decomposition of conducting layer on top of complex fibers. A method for reducing anisotropy by introducing conducting `jumpers', shorting individual fibers or layers of fabric is proposed. The change of anisotropy in the process of fabrication of carbon-carbon composite by passing electric current through fibers has been investigated. In conclusion, alternative uses of CFRP with reduced anisotropy for contact elements of electric current through fibers has been investigated. In conclusion, alternative uses of CFRP with reduced anisotropy for contact elements of electric machines and geological prospecting as imitations of rocks are discussed.
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Anatoliy T. Ponomarenko, Anatoliy T. Ponomarenko, Vitaliy G. Shevchenko, Vitaliy G. Shevchenko, Sergey V. Letyagin, Sergey V. Letyagin, Carl Klason, Carl Klason, "Anisotropy of conductivity in carbon fiber-reinforced plastics with continuous fibers", Proc. SPIE 2443, Smart Structures and Materials 1995: Smart Structures and Integrated Systems, (8 May 1995); doi: 10.1117/12.208323; https://doi.org/10.1117/12.208323
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