DEDALO: Application of Structural Health Monitoring Systems on UHTC Structures

ABSTRACT

In aerospace applications the development of a reliable method of structural health monitoring (SHM) is one of the most important keys in maintaining the integrity and safety of structures, preventing catastrophic failure.

The research program DEDALO aims at developing a real size UHTC-based prototype with a complex shape equipped with a SHM system for damage detection.

A multidisciplinary approach has been adopted involving mechanical design, materials science, manufacturing processes and development of optical devices to detect strain and temperature on the as-produced UHTC articles. Former activities merged into the manufacturing of a prototype hot structure supplied with optical sensing nodes to perform a functional test at high temperature. This communication describes the preliminary findings of the project. A series of ZrB₂-SiC based compositions was studied adjusting type, concentration and granulometry of reinforcing phases and additives to further identify the optimal composition for the hot structure. The pressureless sintering technique was selected privileging a near-net-shape approach to reduce the manufacturing costs.

A SHM system was developed using commercial high temperature Fiber optic Bragg Grating (FBG), for thermal monitoring, and custom silica-sapphire fiber optic strain sensor, based on Fabry-Pèrot configuration, allowing simultaneous and real time measurement of temperature and structural loads applied on the structure under investigation.

A ceramic flexible structure was developed to ease sensor installation procedure on complex shape test articles. The fiber optic sensors interrogation system was developed based on a tunable laser source.

Thermal and mechanical tests showed sensor robustness at high temperature and 0,6 µε as accuracy on strain measurement 0 togliere up to 800°C. Tile-shaped hot structures were manufactured, equipped with the prototype Structural Health Monitoring System (SHMS) and functionally tested at high temperature. The project will undergo a second iterative loop which foresees investigation on the final test article: a ZrB2-SiC based composite hollow tip.

Keywords:

Ultra-high temperature materials, SHMS, thermal protection systems, fiber optic, tip, re-entry vehicle, pressureless sintering, near-net-shape approach.