Monitoring cure and detecting damage in composites with inductively coupled embedded sensors

Abstract

General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. February 2016Abstract. This paper demonstrates the capability of embedded piezoelectric sensors to monitor the state of health throughout the lifetime of composite structures. Sensors were embedded into fibre reinforced composites and used to monitor the progress of cure during manufacture, and the subsequent damage state of the cured part. The sensors used in this work consist of a single piezoelectric transducer, which is electronically connected to an inductance coil. A probe containing two inductance coils was used to make wireless ultrasonic measurements. When the probe was placed in close proximity to an embedded sensor, the electromagnetic coupling between the coils in probe and the embedded coil, allowed electronic signals to be wirelessly transferred between the transducer and the ultrasonic processing equipment. Two different inductively coupled transducer systems (ICTS) were used to monitor cure. A ICTS which generated bulk waves monitored the cure of a thick glass fibre section, and an ICTS which generated guided elastic waves monitored the cure of a large glass fibre plate. To characterise the cure monitoring ability of each ICTS, two established cure monitoring techniques; differential scanning calorimetry (DSC) and dielectric analysis, were used to record measurements during cure. The guided wave ICTS was then used to detect barely visible impact damage (BVID), created by a 10 Joule impact at a distance of 300 mm from the sensor embedded in the large glass fibre plate.

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