Effects of multi-axial Loading on a GW-SHM System for a Composite Fuselage

Kurzfassung

The introduction of composite materials in aeronautics has brought numerous advantages, along with unique damage and failure modes. The structure health is currently ensured by a damage-tolerant design and non-destructive inspections. Among other techniques, Guided Wave-based Structural Health Monitoring (GW-SHM) has gained interest as a cost and time effective alternative to traditional non-destructive techniques. One of the main challenges for GW-SHM is the influence of environmental and operational conditions on the damage identification capability. Aircraft structures undergo a broad range of mechanical load conditions, affecting the GW-SHM system. The study of load influence is meaningful in view of applications where the SHM system is expected to work under varying load conditions. Such applications may be in-flight monitoring, but also on-ground only usage and structural test monitoring. A full‑scale CFRP door‑surrounding structure was instrumented with a GW‑SHM system and subjected to multi-axial dynamic mechanical loading. A hydraulic test rig applied a loading sequence resembling full‑scale fuselage fatigue tests. The resulting dataset contains 27 load combinations derived from the basic load cases. Although it does not capture the full complexity of the load conditions experienced by an aircraft, it provides the needed complexity to evaluate new approaches that address realistic load influences. The test was carried out in a hangar under uncontrolled temperature conditions, which produced a wide range of temperature variations during the experiment as well. This study shows the effects observed by the GW‑SHM system under dynamic multi‑axial load conditions typical of fuselage structures. Finally, it presents a data‑driven approach based on Gaussian Processes to separate the influences of environmental and operational conditions, namely multi‑axial load and temperature, from those of damage.