Ph.D. Thesis Proposal

by

Nunthadech Rodcheuy

(Advisor: Prof. George A. Kardomateas)

ADVANCED HIGH ORDER THEORIES AND ELASTICITY SOLUTIONS FOR

CURVED SANDWICH COMPOSITE PANELS

9:00 AM, Friday, December 16, 2016

Montgomery Knight Building

Room 317

ABSTRACT:

A new one-dimensional Extended High order Sandwich Panel Theory (EHSAPT) for curved panels is presented. The theory accounts for the sandwich core compressibility in the radial direction as well as the core circumferential rigidity. Two distinct core displacement fields are proposed and investigated. One is a logarithmic (it includes terms that are linear, inverse, and logarithmic functions of the radial coordinate). The other is a polynomial (it consists of second and third order polynomials of the radial coordinate) and it is an extension of the corresponding field for the flat panel. In both formulations the two thin curved face sheets are assumed to be perfectly bonded to the core and follow the classical Euler-Bernoulli beam assumptions. Then, the linear elasticity problem formulation and solution for a generally asymmetric sandwich curved beam/panel consisting of orthotropic core and face sheets, which is subjected to a top face distributed transverse loading is presented. The displacement approach is used and the panel is assumed to be simply supported at the ends and closed form solutions for the displacements and stresses are derived. Next, due to the curvature, the first order shear deformation (FOSD) theory for curved sandwich panels is not a direct extension of the corresponding one for flat panels and thus, it is formulated accordingly, and its unique features, such as the reference curve, are discussed. Three versions of the FOSD theory are formulated: the one based on direct variational formulation based on the assumed through-thickness displacement field (termed “basic”), one based on the definition of an equivalent shear modulus for the section (termed “Geq”) and one based on derivation of a shear correction factor, which is considered in conjunction with the equivalent shear modulus. In addition, the classical theory for curved sandwich panels which does not include transverse shear is also presented. The results from following: the new proposed EHSAPT, compressive high order sandwich panel theory HSAPT (from literature), three variants FOSD theory, and Classical theory are compared with Elasticity which serves as a benchmark in assessing the accuracy of the various sandwich panel theories. The case examined is a simply supported curved sandwich panel subjected to a distributed transverse load, for which a closed form elasticity solution is formulated. It is shown that the new EHSAPT is the most accurate (regardless of geometry and material) among other presented theories with the logarithmic formulation is more accurate than the polynomial.