Abstract
The paper aims to investigate the natural frequencies of sandwich plates by means of a Finite Element (FE) formulation based on the Reissner-Mindlin Zig-zag (RMZ) theory. The structures are made of a damaged isotropic soft-core and two external stiffer orthotropic face-sheets. These skins are strengthened at the nanoscale level by randomly oriented Carbon nanotubes (CNTs) and are reinforced at the microscale stage by oriented straight fibers. These reinforcing phases are included in a polymer matrix and a three-phase approach based on the Eshelby-Mori-Tanaka scheme and on the Halpin-Tsai approach, which is developed to compute the overall mechanical properties of the composite material. A non-uniform distribution of the reinforcing fibers is assumed along the thickness of the skin and is modeled analytically by means of peculiar expressions given as a function of the thickness coordinate. Several parametric analyses are carried out to investigate the mechanical behavior of these multi-layered structures depending on the damage features, through-the-thickness distribution of the straight fibers, stacking sequence, and mass fraction of the constituents. Some final remarks are presented to provide useful observations and design criteria.
Highlights
Since its early development and the publication of the first research papers [1,2,3,4,5,6], the FiniteElement (FE) method has shown its potentiality in solving and accurately many structural problems which could not be solved analytically
The free vibration analysis is based on a generalized eigenvalue problem from the analytical point of view
A set of numerical investigations has been presented to describe the mechanical behavior of laminated sandwich plates with a damaged soft-core
Summary
Element (FE) method has shown its potentiality in solving and accurately many structural problems which could not be solved analytically Nowadays, this feature is even more emphasized by the great and continuous technological advancements reached in computer sciences in terms of available computational resources. The damage model is the one illustrated in the book by Lemaitre and Chaboche [21], and it is representative of the formation of microcracks and discontinuities within the considered medium. Since these defects are uniformly distributed and affect the central layer of the plates independently from the direction, this phenomenon is known as “isotropic damage” and it is fully described by a scalar parameter. Further details concerning the phenomenological aspects related to the damage of materials can be found in the book by Reddy and Miravete [22], whereas some structural applications which investigate the effect of damage are illustrated in [23,24,25,26,27,28,29,30,31,32,33]
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