Lessons learned from a broad durability study of an aerospace SHM system

Structural health monitoring (SHM) systems are beginning to be implemented on a variety of aerospace structures. As the application of SHM systems increase, it will be important to define standardized procedures to test durability, reliability, and longevity of the systems. Following a framework (built upon existing durability standards for commercial and military aircraft avionics) developed in previous work, a durability test matrix and testing specifies were developed for a specific sensor system. The lessons learned from a broad range of testing of a surface-mounted piezoelectric Lamb-wave SHM system are presented. Durability testing included mechanical (mechanical strain, hi-cycle actuator fatigue) and environmental (temperature extremes, thermal shock, high humidity, fluid susceptibility, altitude/pressure) loading. Criteria were defined for the tested SHM system to establish whether it had been affected by the various tests. These lessons can help in forming standards specific to SHM systems, such as a supplemental standard geared specifically toward smart structure technologies that would address SHM and other embedded or surface mounted smart structure components and systems. Such a new standard will require contributions from the SHM community, aircraft manufacturers, and regulatory agencies.