Paper number 368

SENSOR TECHNIQUES TO VALIDATE THE STRESS INTENSITY IN CRACKED METALLIC PANELS REPAIRED WITH BONDED COMPOSITE PATCHES

Alan Baker and Bayram Aktepe

Airframes and Engines Division
Aeronautical and Maritime Research Laboratory,
Defence Science & Technology Organisation, Australia

Summary Design of bonded composite patch repairs for cracked metallic components is based on finite element or analytical models that determine the stress intensity K in the cracked component following patching and critical stresses in the patch system. To develop confidence in use of these models for the design of critical repairs there is a need to validate them experimentally.
In this paper a direct experimental approach is described in which K in a patched edge-notched specimen is measured using conventional strain gauges or special K-gauges. Measurements were made at various crack lengths and over a range of temperatures. Generalised Westergaard equations with a rotated axis system were used to determine K from the strain measured using conventional gauges while an empirically derived equation was used for the K-gauge.
These experimental results are encouraging since results for both types of gauges were in reasonable agreement with K predicted using the Rose or the Rose/Wang models.
Keywords Bonded composite repairs, fatigue crack growth; stress intensity factors.

Theme : Repair

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