Fiber-Metal-Laminates (FML) show superior dynamic mechanical properties combined with low densities. The commercially available GLARE has high dynamic properties, crack-arresting functionality and lower density compared to aluminum sheets. Therefore, GLARE is widely used in aviation. The mechanical performance of GLARE can be improved by the substitution of glass fibers with carbon fibers. The carbon fibers feature a higher stiffness combined with a lower density compared to glass fibers. The resulting laminate, CARALL, has possible applications as structural components in aviation. The mechanical properties have to be maintained throughout the lifecycle of the component for it to be reliable.
However, CARALL introduces a mismatch of coefficients of thermal expansion (CTE-mismatch) and the possibility of galvanic corrosion. The FML is optimized by integration of an elastomer interlayer (FMEL) which is desired to solve both problems. The elastomer interlayer is intended to increase the electrical resistance to prevent the development of a galvanic cell and balance the CTE-mismatch.
This study focuses on the effect of galvanic corrosion on CARALL and FMEL and the quantification of the residual mechanical properties. Neutral salt spray tests were carried out in a salt spray chamber for 96 hours according to DIN EN ISO 9227 prior to weight measurements and mechanical testing. The corrosive environment was monitored using zinc comparison standards. The mass deficit of CARALL and FMEL was measured. The galvanic corrosion affects the interfaces of the laminates, therefore study edge shear tests and flexural tests were carried out. The residual strength and consequently the corrosion damage to the laminate were characterized.
The elastomer interlayer was found to inhibit galvanic corrosion of FMEL in the salt spray chamber, whereas the CARALL showed a decrease in mass. Furthermore, the mechanical properties of the FMEL remained constant after the corrosion tests, whilst the CARALLs properties decreased with corrosive loads. The corrosive properties of CARALL were proven to be optimized by integration of an elastomer interlayer, forming the FMEL.