This research directed the application of MEMS technologies, developed by the Politecnico's Department, toward an area not yet sensorized: the tyres of a military aircraft.
The main landing-gear wheels of a military aircraft are characterized by a peculiar phenomenon of tyre heating, generated by severe operational conditions such as the frequent repetition of taxiing, take-off and landing. Structural loads cyclically deform the tyre carcass and induce deformation work in the various layers of materials — bound by the rubber compound — that make up the tyre structure. The internal deformation work and the heat from the brakes raise the internal temperature of the carcass, and even more so in the salient structural area called the bead toe / tyre bead.
Brake-pack temperatures can easily exceed 500 °C in normal braking and reach 1000 °C in an aborted take-off or emergency landing. In extreme conditions the temperature may be high enough to cause local failure of the rubber compound in the tyre-bead area, due to the loss of structural capability of the rubber at high local temperature: structural collapse begins when the bond between carcass and steel cable loosens. This phenomenon, not measurable on the outer tyre surface, remains hidden because of the rubber's poor heat conductivity. Hence the need for a dedicated MEMS sensor system able — using the salient physical parameters affecting bead structural integrity — to:
- monitor taxiing, take-off and landing over the entire operating cycle of an aircraft;
- store the operating history in terms of the significant parameters.
Results and next steps
The research made it possible to develop a device inserted into the tyre, able to monitor and collect data on thermal conditions and wear in real time. The system was realized through MEMS sensors integrated into the tyre itself, monitoring the operating environmental conditions (temperature, pressure, loading conditions). The level reached by the current state of research is TRL 5.
The next steps are directed at engineering a final, optimized "stand-alone" solution for an initial operational test of the entire system on an aircraft, for ground trials.