Creep Age Forming (CAF) has been successfully used to manufacture thin wing skins. Now the technology is being developed to fine-tune the shape of thick, geometrically complex, single-piece cockpit fuselage sections. This application involves forming a new advanced aluminium alloy previously deformed by High Energy Hydro Forming (HEHF).

CAF applies heat and mechanical pressures to refine the aerodynamic profile of a component, whilst age hardening the material to the final temper condition. Significant cost and weight savings have been demonstrated with this technology as it allows for the production of large, complex, integral components, thereby reducing assembly and joining operations.

The accumulation of dislocation creep results in a permanent change of shape and stress relaxation response, occurring alongside the precipitation hardening that strengthens the alloy. A complex interplay exists between these two effects, as ageing inhibits creep. The creep relaxation response of the damage tolerant alloy AA2139 will be characterised to attain a robust understanding of the materials creep response and sensitivity to pre-strain.

A combination of elevated-temperature stress relaxation tests and microstructural characterisations, throughout the ageing sequence, will be used to develop a creep relaxation material model. This model should improve the capability to predict final geometry after springback.