Free vibration analysis of sandwich plates by component-wise approach

This paper presents a comparative analysis of the linear response of sandwich structures with honeycomb cores, evaluated through different theoretical formulations implemented employing the Carrera Unified Formulation (CUF). This framework makes it possible to generate models with different levels of refinement, ranging from simplified to fully detailed descriptions. If the total structure is considered as a single layer, the Equivalent-Single Layer (ESL) is employed; if the skins and core are considered as components, the Layer-Wise (LW) is used; finally, the actual geometry of the core can be considered, along with the skin, leading to the Component-Wise (CW) approach. The research aims to assess the impact of the simplifications inherent in the ESL and LW models on the accuracy of modal predictions relative to the more detailed CW approach. A benchmark case is analysed, and its natural frequencies and mode shapes are computed using all three approaches and compared with results obtained from commercial two- and tree-dimensional finite elements. The outcomes reveal that although the ESL and LW models are computationally efficient and can capture the global deformation of the structure, they fail to address local effects, which are accurately predicted by the CW model. The latter, hence, is necessary to provide precise information about the dynamic behaviour of the honeycomb sandwich structure. In particular, Modal Assurance Criterion (MAC) values between the modes of the skins assessed by means of LW and CW, show that even if a global mode shape can be well represented by LW, local effects can only be detected by CW approach. This difference introduce an underestimation in the evaluated frequencies, which achieves -19 % and -10 % in case of bending and torsional modes within the first ten modes, respectively. Given the widespread use of honeycomb sandwich panels in aerospace structures for their high stiffness-to-weight ratio and vibro-acoustic insulation properties, the results underline the importance of adopting refined CW-based CUF models whenever accurate predictions of the dynamic response are required.