On the modal behaviour of ultralight composite sandwich automotive panels

The effects of vibrations in vehicles range from simple noise and reduced comfort, to decreased performance, from wear and material fatigue to irreversible failures and danger. A study of the dynamic behaviour of reinforced composite panels is here presented, applied to the construction of an ultralight photovoltaic roof in the case of a solar sport car. This is an extreme race prototype where design and materials solutions, as high strength carbon fiber reinforced polymers and sandwich-structured composites, were addressed to optimize the stiffness-to-weight ratio. A modal analysis was performed considering materials anisotropies by a layered-shell finite element model and through-the-thickness integration points with the scope to discretize the multi-layered sandwich structure. Additional aspects, as gravity force and external constrains, were also included. Experimental evidences were used for validating the numerical model and underscored an outstanding accuracy. The same design procedure was finally applied to change the preexisting structural solution achieving an optimized roof that was manufactured, installed and tested.