Concepedia

Abstract

Piezo-electric (PVDF) sensors were applied to a specifically prepared two-sided composite specimen. The specimen was fatigued with a 3Hz cyclic load until the adhesive bond between composite patch and aluminium failed. During the cyclic loading period the output from the PVDF sensors were monitored by a prototype "Smart Patch Device". The Smart Patch Device measured outputs from two PVDF sensors, one on the "patch" and one in the "far-field" from which was calculated a "Patch state of health". The Smart Patch Device successfully detected the composite patch disbonding from the aluminium. The effect of the adhesive spew fillet, which can produce significant strains in disbonded sections of patch, is considered. Finally a number of points in relation to the use of the strain ratio technique for patch state of health monitoring are elucidated..