Abstract
An alternative elastoplastic model based on the Flory’s right Cauchy-Green stretch tensor decomposition is proposed and applied to model soft cores of sandwich panels. It does not follow usual methodologies as the additive decomposition or the Kröner-Lee multiplicative decomposition of strains. It is based on an important hyperelastic relation, Flory’s decomposition, from which the total strain is separated in two isochoric and one volumetric parts. Using this decomposition, the volumetric strain energy continues to be elastic during all elastoplastic analysis and the isochoric parts are managed to produce the plastic evolution. As a consequence of Flory’s decomposition, the plastic flow direction is known and independent of the yielding surfaces. Moreover, it provides the well known deviatoric nature of plastic strains. For validation purposes, the resulting formulation is implemented using a special 3D prismatic element in a geometrical nonlinear positional FEM computational code. The achieved numerical results are compared with literature experimental data of soft core laminated structural elements.
Highlights
The study of laminated beams, plates and shells is very extensive as it is motivated by the high importance of this type of structural arrangement in the mechanical, aeronautical, marine and civilindustries
In order to find recent reviews readers are invited to consult, for example, the work of Abrate and Di Sciuva (2017) for general Equivalent-Single-Layer theories (ESL), Caliri et al (2016) for FEM shell theories, Garg et al(2021) to access theories including functionally graded materials, Nsengiyumva et al (2021) for a review associated with non-destructive experimental analysis and the work of Sayyad and Ghugal (2017) for vibrations and stability of laminated beams and plates
The present study is dedicated to propose an elastoplastic model for the analysis of soft cores usually present in sandwich panels
Summary
The study of laminated beams, plates and shells is very extensive as it is motivated by the high importance of this type of structural arrangement in the mechanical, aeronautical, marine and civilindustries. The soft cores of sandwich panels are usually made of polymers and, have a nonlinear behavior This physical nonlinearity is present in both elastic and plastic phases and greatly limits the use of most laminate theories cited by the above mentioned literature reviews. In this area one may cite works of Atluri (1984), Hughes and Winget (1980), Kojic and Bathe (1987) and Bruhns et al (1999) that present alternatives to solve objectivity problems that arise from the additive decomposition since the pioneering work of Argyris and Kleiber (1977) Even with these improvements, the application of hypoelastic formulations is limited to materials that present small elastic strains, which is not the case of soft cores. The applications in sandwich panels, in which the finite plasticity occurs in the core, are compared with experimental results present in specialized literature, demonstrating the precision and applicability of the proposed model
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