The current design practice of composite material aeronautical structures imposes the use of knock-down structural material allowables to take into account the high sensitivity to environmental exposure (i.e., moisture, temperature, damages). The “moisture derating factor” comes from specific mechanical test campaign and drastically reduces the advantage of using such materials; but the continuous monitoring of the moisture content of the structure could enable the use of higher design allowables. In the framework of FUSIMCO (Work developed within the frame of the Project FUSIMCO-FUSoliera Ibrida Metallo COmposito-co-financed by MIUR-Italian Ministry of Research with DAC-Campania Aerospace District as beneficiary and Leonardo Company-Aerostructure Division as “prime” partner) project, the aim of this study is to verify the effectiveness of the impedance measurement method as a health-monitoring tool to evaluate the moisture quantity absorbed by an aeronautical composite structure. The method is based on the idea that a composite laminate can be associated with an equivalent electric circuit (EEC). Some electrical characteristics of this EEC can be associated to the moisture content of the laminate. A simple EEC model, mainly capacitive, was used. A frequency sweep was the electric stimulus signal of some electrodes, glued onto the specimens to investigate the EEC parameters variation with respect to the induced moisture content variation (gravimetrically determined). The study confirmed the possibility of effectively using the impedance measurement method as a health-monitoring tool for moisture content evaluation of a composite laminate.

The work at hand illustrates the design approach adopted for a large strain sensor, based on the carbon nanotube (CNT) technology, devoted to operations of structural health monitoring and shape reconstruction. After a critical discussion on the specifications, the most suited materials and processes were selected, with specific focus on the dispersion and deposition strategies. Then, by means of a FE approach, the topology in terms of CNT volume concentration, morphology (curvature) and orientation, was identified. A feasibility study on the manufacturability was then carried out. Finally, in compliance with the initial specifications, the set of calibration and space qualification tests was illustrated. The above mentioned activities were developed within the Project “Graphene-Polymeric Spray Sensor for Shape Recognition of Super-Deformable Structures”, GRAPSS, sponsored by CIRA within the “Curiosity Driven” initiative.