Experimental Modal Testing of Lightweight Composite UAV Structures: Methods and Key Challenges

This study aims to conduct and experimental modal analysis of a very lightweight composite structure representative of UAV application and to evaluate the suitability of different testing approaches for reliable identification of its dynamics characteristics. The investigated structure is a winglet made of carbon fibre reinforced polymer (CFRP) with a lightweight foam core. The experimental campaign was based on impact hammer excitation combined with triaxial accelerometer measurements. Modal test were performed under three different boundary conditions: free-free suspension using elastic cords, free-free approximation using compliant foam support, and fixed conditions reflecting to the operational mounting of the winglet. The objective of the study is not only to identify natural frequencies and mode shapes, but primarily to assess the influence of support conditions, excitation quality and measurement-induced mass loading on the reliability of the extracted modal parameters. By comparing the obtained frequency response functions and modal characteristics across different test configurations, the work seeks to identify the most appropriate experimental approach for modal analysis of ultra-lightweight composite UAV structures, providing practical guidance for future vibration investigations.