Reliability of Co-Bonded Piezoelectric Sensors on CFRP Structures

Abstract

In order to replace conventional Non Destructive Testing (NDT), SHM needs to be at least as reliable and cost effective as the competing NDTTechnology. The reliability of the permanently installed sensor is among others pending on the link between sensors and structure. In the past years an alternative to the current secondary bonding process has been investigated, the co-bonding of sensors. The co-bonding shall reduce the recurring costs for sensor installation compared to secondary bonding while keeping the reliability on the same level. Co-bonding is leading to several benefits regarding the manufacturing process, as the sensors are applied outside the critical production path, but is leading at the same time to challenges regarding sensor and process requirements. In past work, it has been demonstrated that piezoelectric sensors do have the capability for co-bonding. In the present work, adjunctive issues are outlined. This comprises to prove that the sensors do not derate the mechanical properties of the adherent CFRP material and to verify the durability of the sensors. Both, proof of non-disturbance and sensor durability, are demonstrated by mechanical tests on coupon level. Over 400 coupons are tested at different locations within Europe in the frame of the EU funded project SARISTU, of which this paper is presenting a selection of first results. Other important tasks, as the sensor network connection and protection are touched and an outlook is given.