Enhanced bondline thickness analysis for non-rigid airframe structural assemblies

Date

2019-05-13

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Department

Type

Article

ISSN

1270-9638

Format

Free to read from

Citation

Elsevier

Abstract

Adhesive bonding is a proven alternative to mechanical fasteners for structural assembly, offering lighter and thus more fuel efficient aircraft and cost-effective manufacturing processes. The effective application of bonded structural assemblies is however limited by the tight fit-up requirement, which is with sub-mm tolerance and can be a challenge for the industry to meet considering the variability of current part manufacturing methods and the conservative nature of the conventional tolerance stack-up analysis method. Such a challenge can discourage effective exploitation of bonding technologies, or lead to development of overengineered solutions for assurance. This paper addresses this challenge by presenting an enhanced bondline thickness variation analysis accounting for part deflection of a bonded skin-stringer assembly representing a typical non-rigid airframe structure. A semi-analytical model accounting for unilateral contact and simplified 1D adhesive flow has been developed to predict bondline thickness variation of the assembly under two typical curing conditions: namely autoclave curing and out-of-autoclave curing. The effects of component stiffness and manufacturing variations on bondline thickness are investigated by incorporating stringers of different stiffness, as well as shims of different thicknesses in-between the skin and stringer, in the stringer-skin assembly. A small-scale bonding demonstrator has been built and the physical results are in good agreement with the model prediction. It has been demonstrated that the part deflections need to be accounted for regarding fit-up requirement of bonded non-rigid structural assembly. The semi-analytical model offers more reliable and realistic prediction of bondline thickness when compared to a rigid tolerance stack-up. The analysis method presented can be a major technology enabler for faster, more economical development of the aircraft of the future, as well as of any analogue structures with high aspect ratios where weight savings and fatigue performance may be key objectives.

Description

Software Description

Software Language

Github

Keywords

Non-rigid assembly, Bonded airframe structure, Bondline thickness, Adhesive flow, Direct linearization method, Quadratic programming

DOI

Rights

Attribution 4.0 International

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