Effect of various surface treatment methods on the flexural properties of fiber metal laminates

Fiber metal laminates (FMLs) are a new group of composite materials that consist of alternating thin laminates of metals and fiber reinforced polymeric composites. FMLs combine the advantages of metals and polymeric composites. In order to enhance the interfacial bonding between the alternating laminates, various surface treatment methods can be used on the metal surfaces. In this research, FMLs of alternating laminates of aluminum/epoxy-basalt fibers were fabricated using hand lay-up method. The effect of various surface treatment methods of mechanical and chemical (consist of alkaline and sulfochromic etching) on the flexural properties of the fabricated FMLs were investigated with three-point bend tests. SEM were utilized to investigate surface morphology of aluminum. Results showed that the sulfochromic etch method brought about a significant improvement in the flexural strength, strain to failure and absorbed energy in comparison to the mechanical and alkaline methods. Difference in flexural behavior of samples is attributed to their aluminum surface morphology. SEM observations showed that sulfochromic etch method created a porous layer on the aluminum surfaces. This porous layer provided channels for the epoxy resin to fill in, creating better adhesion and a much stronger mechanical interlocking between the laminates.