21st Congress of International Council of the Aeronautical Sciences, Melbourne, Australia, 13-18 September, 1998
Paper ICAS-98-5.3.1

BOND DURABILITY PERFORMANCE -THE AUSTRALIAN SILANE SURFACE TREATMENT

Arnott D. R., Rider A. N., Olson Jacques C. L., Lambrianidis L. T., Wilson A. R., Pearce P. J., Chester R. J., Baker A. A., Morris C. E. M., Davis M. J.*, Swan G.*
Aeronautical & Maritime Research Lab., Australia; *RAAF, Australia

Keywords: bond durability performance, silane surface treatment

The Royal Australian Air Force (RAAF) has produced its own Engineering Standard on Composite Materials and Adhesive Bonded Repairs (RAAF ENG STD C5033) as a consequence of procedure and process deficiencies contained in the manufacturers' Structural Repair Manuals. The surface preparation principles underpinning this standard were established during the development of the Australian silane surface treatment. This paper examines the purpose of each step in preparing the adherend for bonding and its effect on the durability performance. In addition, the durability performance and locus of failure of bonds can be described in terms of a two step model. The first step involves controlled moisture ingress by stress-induced microporosity of thee adhesive in the interfacial region. The second step determines the locus of fracture through the relative dominance of one of three competitive processes, viz: oxide degradation, polymer desorption, or polymer degradation. A key element of the model is the control exercised over porosity by the combined interactionoff stress and the relative densities of strong and weak linkages at the metal to adhesive interface. The model has the potential for development as an engineering management.

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