Liquid detection in confined aircraft structures based on lyotropic percolation thresholds

In aircraft, aqueous liquids arising from spillage, condensation or rainfall during boarding can result in heavy corrosion of structural parts. This is especially the case for the so-called floor structures in the passengers cabin. A reliable sensor for detecting aqueous liquids which is interrogated at least on a weekly base, or even more frequently, could help to reduce repair and maintenance costs considerably. An important challenge for the installation of sensors in the floor beam area is the limited space available. Furthermore, the sensor has to cover an extended area. To achieve this target, an organo-ceramic composite was developed containing a conducting compound (conducting ceramic powder) which is embedded in a hydrophilic matrix. The functionality of the sensing material is based on the collapse of percolation conductivity of the composite. When the composite is exposed to aqueous liquids, the conductivity is essentially lost by sorption and swelling of the matrix material. Sorption experiments indicate that the loss of conductivity could be triggered, or at least promoted by a lyotropic glass-rubber transition in the hydrophilic matrix. The applicability of the integral system was shown on lab-scale, and a sensor network is already implemented and tested in an operational commercial airliner. (C) 2011 Elsevier B.V. All rights reserved.