Triboluminescent composite with in-situ impact sensing capability

Abstract

This work reports a preliminary study that demonstrates the use of the in-situ triboluminescent optical fiber (ITOF) sensor for in-situ and distributed monitoring of barely visible impact damage (BVID) in composites. Currently, damage detection in composites is primarily by visual inspection and other nondestructive evaluation (NDE) techniques such as tapping, ultrasonic Cscan, X-ray, thermography and eddy current. These NDE techniques are however not in-situ in the structure and consequently require expensive and extended system downtime for postdamage inspection and assessment. Firstly, the impact sensing capability of two different sensor configurations, namely 30 % and 50 % ZnS:Mn (wt) content, was investigated with an automated impact hammer system and scanning electron microscope. Secondly, the ITOF sensor was integrated into carbon fiber reinforced polymer (ITOF-CFRP) panels during composite part manufacturing to create a composite system with in-situ damage sensing capability. The real time and distributed damage sensing capability of the fabricated ITOF-CFRP panels were then studied by subjecting them to impact loads. Both sensor configurations exhibited linearity in terms of the applied impact loads and the corresponding triboluminescent (TL) responses during direct impact loading. The ITOF sensor with 50 % ZnS:Mn (wt) content however exhibited higher sensitivity than the ITOF sensor with 30 % ZnS:Mn (wt) content. In-situ and distributed impact load and damage detection was successfully demonstrated in the fabricated ITOF-CFRP panels. The low velocity impact test results indicate that the magnitude of the impact load as well as the impact location on the structure relative to the position of the integrated ITOF sensor determine the magnitude of the observed TL signals from the sensors in the ITOF-CFRP panels. Further work is ongoing to better characterize and model the impact load, the sensor signals and the damage in a composite structure. When the ITOF sensor system is fully developed, there is the hope of equipping large composite structures like aircraft and wind blades with in-situ and distributed damage monitoring capabilities that can enhance their performance and users' safety.

Publication Title

CAMX 2015 - Composites and Advanced Materials Expo

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