Adhesive properties of thermoset fibre metal laminates

Master Thesis


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University of Cape Town

Fibre metal laminates (FMLs) are composite materials that consist of layers of metal and fibre reinforced polymers. FMLs are used in the construction of aircraft fuselage skins, such as the Airbus A380. GLARE, the only commercially available FML, is of particular interest due to its damage tolerance and potential impact and blast resistance. GLARE is not commercially available and attempts at manufacturing FMLs similar to GLARE at the Blast Impact Survivability and Research Unit (BISRU) laboratories have been unsuccessful. The FMLs readily exhibited debonding between the aluminium and glass fibre reinforced epoxy, often upon handling prior to impact or blast events. The purpose of this study was therefore to investigate manufacturing techniques in order to produce FMLs that would be able to withstand impact and blast loads. Adhesive surface pre-treatment techniques and manufacturing methods typically employed in aircraft construction were investigated with particular emphasis on the adhesion of aluminium to epoxy in FMLs. This interface was of particular interest as good bonding facilitates load transfer under dynamic loading and was identified as the point of failure of the previously manufactured FMLs. The effects of surface treatment techniques used to enhance adhesion were investigated under quasi-static conditions using Single Leg Bend tests. Chemical surface treatments such as alodining, etching, anodising, silane treatments and combinations thereof were investigated. The effect of resin and the inclusion of a film adhesive were also investigated. The silane treatments were identified as the chemical treatments that provided the best adhesion, however the film adhesive significantly improved the fracture toughness regardless of the chemical surface treatment.

Includes bibliographical references.