Electrical properties of aluminium-fibre reinforced composite laminates
Barbara Surowska, Monika Ostapiuk
Quarterly No. 4, 2016 pages 223-229
DOI:
keywords: CFRP, FML, surface resistivity, contact resistivity
abstract Hybrid materials such as Fibre Metal Laminates (FMLs) containing carbon fibre reinforced polymers (CFRPs) are very attractive candidates for novel design strategies due to their specific properties. However, Fibre Metal Laminates (FMLs) may be susceptible to galvanic and electrochemical corrosion in a damp environment due to the applied metal sheets. Aluminium alloy-glass/epoxy composite FMLs exhibit high corrosion resistance. Their corrosion process is limited to the metal outer layers if they are not protected because glass fibre reinforced composites are non-conductive. Galvanic corrosion initiation is likely when a composite contains carbon fibres, owing to the electric conductivity of these fibres. Therefore, it is necessary to determine the electrical properties of the produced hybrid materials. Measurements were made to determine the surface resistivity of components and contact resistivity of the laminates. Investigations were conducted on on a polymer composite and FMLs consisting of aluminium 2024-T3 joined with GFRPs (R-glass, S-glass) and CFRP. The aluminium alloy sheet was anodized in a sulphuric acid solution (SAA process). The composite plates and hybrid laminates were cured in the autoclave process. The surface resistance of the materials was determined by measuring the drop in current using the two probe method and strip electrodes. In the laminate specimens, the electrodes were placed in the longitudinal direction between the corresponding layers. The interlaminar interface properties of these laminates were studied by measuring the contact electrical resistivity of this interface. Moreover, the variation in temperature with time during electrical measurements was recorded by means of the thermovision technique for the composite specimens. This study revealed that the aluminium oxide and GFRP-R composite are insulators with very high but negative surface resistivity. The surface resistivity of the CFRP composite is equal to about 102÷103Ω/ı and depends on the direction of the fibres. When the electrodes are located perpendicularly to the fibres, the surface resistivity is lower and the surface temperature increases locally. Generally the contact resistivity of this composite is ~103 times higher than indicated in literature. It is a result of the high quality of the prepreg and autoclave curing of the laminate. The measurements of electrical contact resistivity indicated that it is possible to obtain a dielectric interface between the aluminium alloy and carbon reinforced composite by anodizing the aluminium and applying aglass prepreg layer 0.25 mm thick. The thinner glass composite layer does not increase the in-plane contact resistivity.