Fracture behaviour of metal-composite joints

The fracture behaviour of polymer composite-metal joints has been investigated within the context of two real joint applications. A joint intended for the joining of a glass-fibre reinforced vinylester composite (GRP) superstructure to the steel deck of a naval vessel was the starting point for the project. The novel technique lies in the manufacture of the joint in that a steel adherend is incorporated into the superstructure panel during the manufacture of the panel itself by a resin infusion moulding process. One end of this adherend protrudes from the finished panel which can then be welded to the steel deck. The vinylester matrix resin thereby acts as the sole source of adhesion at the composite-metal interface. Characterisation of the mechanical response of this joint highlights the influence of the toughness of the GRP on the joint behaviour. The fracture behaviour of this interface is then investigated to establish the effects of steel surface roughness and heating. Accelerated ageing of the joint in salt and distilled water is carried out and the effect of the GRP mechanical properties and joint mechanical response evaluated. A second application considered has been the joining of a titanium adherend to a carbon-fibre reinforced epoxy composite adherend for use in a racing car suspension system. A comparison of the effectiveness of different titanium surface treatments is made in terms of the surface profile and oxide thickness. A range of adhesive layer thicknesses are used in the manufacture of the joints and the effects of this and the surface treatment on the fracture behaviour are determined. The main conclusions drawn are that the principal factors affecting fracture behaviour of metal-composite joints are adherend surface chemistry, moisture absorption, exposure to elevated temperature, and joint design.EThOS - Electronic Theses Online ServiceGBUnited Kingdo