The tiltrotor wing structure is one of the most critical and thoroughly investigated components in aircraft design due to the interactions between the wing, pylon, and rotor systems, which are crucial for ensuring aeroelastic stability. In this context, composite materials are essential for meeting structural requirements while also minimizing weight. The reference aircraft for this study is the Next-Generation Civil Tiltrotor Technological Demonstrator (NGCTR-TD), developed by Leonardo Helicopters within the Clean Sky 2 research program. An innovative wing box configuration featuring three spars, including one curved spar, was designed and manufactured. Given the uniqueness of this tailored solution, it is crucial to ensure that the manufactured assembly meets the design requirements. In the field of structural dynamics, experimental modal analysis is essential for determining experimental modal parameters to satisfy these requirements. Several experimental tests on lab-scale demonstrators and incomplete full-scale mockups were conducted to validate the test setup and approach. Finally, preliminary vibration testing activities have been performed on the full-scale test article, thus validating the test setup in view of the final test.