Terry Hause

Recent developments in the modeling and behavior of advanced sandwich constructions: a survey

A general overview of some recent developments related with the modeling and stability of sandwich structures is presented in this paper. The survey covers a number of issues related with the geometrically linear and non-linear formulations of curved and flat sandwich constructions featuring laminated anisotropic face sheets, and associated stability problems. Issues related with the enhancement of the load carrying capacity of sandwich panels resulting in the increase of the buckling strength, the reduction of the intensity of a snap-through buckling and even of its removal are also addressed. The provided list of references is not exhaustive, in the sense that it is mainly connected with topics of sandwich constructions in which the first author of this paper has been involved during a good part of his research activity. Moreover, the displayed results illustrating some basic trends concern not only the ones previously obtained by the authors of this survey-paper, but also several others, presented here for the first time.

Postbuckling of anisotropic flat and doubly-curved sandwich panels under complex loading conditions

Abstract A study of the postbuckling behavior of geometrically imperfect anisotropic sandwich doubly-curved and flat panels subjected to a system of compressive edge loads and a lateral pressure is presented. The study is carried out in the context of the weak core sandwich shell model whose superior structural performance as compared to those of the strong core sandwich or standard laminated structures has resulted in its increased use in the design of advanced flight vehicles. A detailed investigation of the influence played by a number of kinematical and physical parameters as well as by the character of tangential boundary conditions on the load carrying capacity of sandwich structures is performed and pertinent conclusions are outlined.

Geometrically Nonlinear Theory of Initially Imperfect Sandwich Curved Panels Incorporating Nonclassical Effects

A comprehensive geometrically nonlinear theory of initially imperfect doubly curved sandwich shells is developed. The theory encompasses sandwich structures with dissimilar face sheets constructed of laminate composites and with the core modeled as an orthotropic body featuring strong or soft behaviors. The theory includes the dynamic as well as the temperature and moisture effects. As a special case, a range of related applications of the theory of sandwich shells with soft core are presented. These involve the buckling and postbuckling of flat and circular cylindrical shells compressed by uniaxially edge loads, and the influence played in this respect by a number of geometrical and physical parameters is highlighted. Also contained are comparisons of buckling results obtained in the context of the present theoretical model with the ones obtained experimentally, and reasonable agreements are reported.

Effect of Face-Sheet Anisotropy on Buckling and Postbuckling of Sandwich Plates

Astudy oftheeffectofanisotropyoffacesheetsonbuckling andpostbuckling ofsandwiche atpanelssubjected to both mechanical and thermal loads is presented. Themechanical loadsconsist of uniaxial compressive/tensile edge loads, while the temperature is assumed to exhibit an antisymmetric variation through the panel thickness. The study iscarried outin thecontextofa geometrically nonlinear theory of sandwichstructuresthat also incorporates the effect of unavoidable stress-free initial geometric imperfections. A detailed analysis of the ine uence of a large number of parameters associated with the panel geometry, material properties of the core, e ber orientation and stacking sequence in the face sheet, and character of tangential boundary conditions (i.e., movable or immovable ) on buckling strength and postbuckling response is accomplished, and pertinent conclusions are outlined.

Non-linear response of geometrically imperfect sandwich curved panels under thermomechanical loading

Abstract This paper deals with the non-linear response of sandwich curved panels exposed to thermomechanical loadings. The mechanical loads consist of compressive/tensile edge loads, and a lateral pressure while the temperature field is assumed to exhibit a linear variation through the thickness of the panel. Towards obtaining the equations governing the postbuckling response, the Extended Galerkin’s Method is used. The numerical illustrations concern doubly curved, circular cylindrical and as a special case, flat panels, all the edges being simply supported. Moveable and immoveable tangential boundary conditions in the directions normal to the edges are considered and their implications upon the thermomechanical load-carrying capacity are emphasized. Effects of the radii of curvature and of initial geometric imperfections on the load-carrying capacity of sandwich panels are also considered and their influence upon the intensity of the snap-through buckling are discussed. It is shown that in special cases involving the thermomechanical loading and initial geometric imperfection, the snap-through phenomenon can occur also in the case of flat sandwich panels.

Buckling and Nonlinear Response of Sandwich Curved Panels to Combined Mechanical Loads-Implications of Face-Sheet Elastic Tailoring

Results concerning the linear and nonlinear static response of curved sandwich panels to combined mechanical loads are addressed, and in this context, the implications of elastically tailored face-sheets upon the enhancement of their load carrying capacity are emphasized. The analysis is based on a geometrically nonlinear theory of shallow sandwich shells restricted to the case of small strains and moderately small rotations. In addition to the implications of ply-angle, ply-sequence and ply-thickness of composite face-sheets, those related with the panel curvature and aspect ratio on their buckling and nonlinear static response are analyzed, and pertinent conclusions are outlined.

THERMOMECHANICAL LOAD-CARRYING CAPACITY OF SANDWICH FLAT PANELS

The study of the nonlinear response of sandwich flat panels exposed to thermomechanical loading systems is the topic of this article. The sandwich structure considered in this article consists of a thick core layer bonded by the face layers, which are assumed to be symmetrically located with respect to the midplane of the overall structure. The loads involved in this analysis consist of biaxial compressive edge loads, a lateral pressure, and a nonuniform temperature field. The effects of the unavoidable initial geometric imperfections and the character of tangential boundary conditions are incorporated, and their implications upon the structural response are explored. In short, the results of this study are intended to provide pertinent information on the thermomechanical load-carrying capacity of flat sandwich structures.

THERMOMECHANICAL POSTBUCKLING OF GEOMETRICALLY IMPERFECT FLAT AND CURVED SANDWICH PANELS

This paper is concerned with the postbuckling of flat and curved sandwich panels under thermomechanical loadings. The mechanical loads consists of compressive/tensile edge loads, and a lateral pressure while the temperature field is assumed to exhibit a linear variation through the thickness of the panel. Towards obtaining the equations governing the postbuckling response, the extended Galerkins method is used. The numerical illustrations concern doubly-curved, circular cylindrical and flat panels of quadratic projection on a plane, all the edges being simply-supported. Moveable and immoveable tangential boundary in the directions normal to the edges are considered and their implications upon the thermomechanical load carrying capacity are emphasized. Effects of the radii of curvature and of initial geometric imperfections upon the load carrying capacity of sandwich panels are also considered and their influence upon the attenuation of the intensity of the snap-through buckling are discussed. It is shown that in special cases involving the thermomechanical loading and initial geometric imperfection, the snap-through phenomenon can occur also in the case of flat sandwich panels.

Doubly Curved Anisotropic Sandwich Panels: Modeling and Free Vibration

Problems related with the modeling and behavior in free vibration of doubly curved sandwich panels with laminated face sheets are developed in this paper. Implications of anisotropy and stacking sequence of face sheets as well as of transverse orthotropy of the core on the free vibration behavior are highlighted. Other parameters, mainly geometrical ones, are also considered in the numerical simulations, and their implications on the vibrational behavior are put into evidence. Because of the absence of similar results in the specialized literature, this paper is likely to fill a gap in the state of the art of this problem and provide pertinent results that are instrumental in the design of advanced sandwich shells.

Doubly-Curved Anisotropic Sandwich Panels Impacted by an Explosive Blast: Modeling and Response Behavior

Problems related with the modeling and dynamic response to blast loadings of doublycurved sandwich panels with laminated face sheets are developed. In this respect, the implications the panel curvature, of anisotropy and stacking sequence of face sheets, as well as of transverse orthotropy of the core, and of structural damping ratio are highlighted. As concerns that blast pulses considered in this analysis, these are due to either in-air explosions or of traveling shock-waves. Other parameters, mainly geometrical ones are also considered in the numerical simulations, and their implications on the dynamic response are put into evidence. Due to the absence of similar results in the specialized literature, this paper is likely to ll a gap in the state of the art of this problem, and provide pertinent results that are instrumental in the design of advanced sandwich shells operating in a dynamic environment.