RESEARCH AND TECHNOLOGY FOR ADVANCED NAVAL STRUCTURES

Yapa D. S. Rijapakse

Office of Naval Research, Ship Structures Division (ONR 334), 800 N. Quincy Street, Arlington, VA 22217-5660, USA

An overview will be presented of current research and development activities at the Office of Naval Research aimed at the establishment of the scientific basis required for the design of affordable ship structures, which are reliable, durable, and stealthy. Composite sandwich construction plays a significant role in these activities. Multi-functional multi-layered composite structures are used with embedded sensors and antennas in some applications. Examples of recently developed structures will be provided, including an advanced enclosed mast structure. Research in composite materials and composite sandwich structures will also be discussed, including recent advances in dynamic failure modes and dynamic failure criteria. Real time investigations of highly dynamic deformation and failure phenomena have been facilitated by the innovative coupling of refined full-field optical techniques and high speed photography. Thermodynamic aspects of dynamic events have also been investigated utilizing infra-red sensor arrays to permit full-field temperature fields.

SANDWICH CONSTRUCTIONS - DESIGN AND EXPERIENCE

Karl-Axel Olsson

Department of Aeronautics, Division of Lightweight Structures, Royal Institute of Technology Stockholm, Sweden

Twenty-five years ago most commercial and naval vessels were built of steel. For military vessels with high speed requirements high tensile steel was used quite early compared to what was common for normal commercial shipbuilding. In the beginning if the 1970s it was relatively unusual that small commercial vessels were built in higher steel qualities. High-speed vessels are weight sensitive structures. This makes the use of composite structures interesting also for large fast-going ferries. In order to reduce hull weight as far as possible, several ferries have been built in high-strength aluminium alloys, which have almost the same strength as some high tensile steel qualities, but only the third of the weight. Twenty-five years experience from FRP-sandwich design of marine and commercial ships built in Scandinavia will be discussed in the paper. A reduction of the hull weight with about 50% is normally reached for marine vessels compared to conventional structures in wood or steel. Use of more advanced materials (carbon fibers, more ductile matrix materials and foam cores) and new manufacturing technology (vacuum-assisted RTM) have showed that it is possible to reduce the weight even more, with the same structural requirements. Other positive effects are low maintenance cost, good thermal insulation, shock resistance, and other integrated functions. The negative side of the use of FRP sandwich will also be mentioned, like fire problems, smoke emission, joints, load introduction and non-destructive testing. The use of FRP sandwich in offshore structures has just begun; deck panels and some protective structures have been built. Experience from other application fields will also be discussed, i.e. containers, refrigerated tanks, cars, trucks, busses, railroad waggons, and buildings.

SANDWICH IN MARINE STRUCTURES – CHALLENGES AND SOLUTIONS FOR THE STRUCTURAL DESIGNER

G Holm,

VTT Manufacturing Technology, Espoo, Finland

The potential of sandwich structures in weight critical applications is highlighted together with aspects behind the need for lightweight structures. An overview is included of the most important factors considered critical in a choice between FRP sandwich and other structural materials for lightweight structures. The importance of an objective evaluation of different material alternatives is underlined. Special attention is paid on the possibilities offered by a thorough analysis of the key factors behind the widely used maximum deflection and minimum face thickness criteria. The challenges, when moving forward and beyond established, traditional and well proven concepts, identifies and highlights the most urgent questions to be solved by research efforts in the near future.

PRACTICAL ASPECTS ON STRUCTURAL ANALYSIS OF A WEIGHT OPTIMIZED FRP-SANDWICH

STEALTH CORVETTE

Sven-Erik Hellbratt and Sten Vallbo

Surface Ships /Hull, Kockunis AB, Karlskronavarvet, Karlskrona, Sweden

This paper presents experience gained in the development of the structure of the FRP-sandwich full stealth Visby class corvette. The chosen material concept, carbon fibre/vinyl ester laminates separated by a PVC foam core, was found to fulfill the requirements of structural strength and an integration of stealth qualities into the structure. New approaches concerning loads together with the large number of variables in the material concept have called for an extensive use of FEA in order to weight optimize the structure. The use of FEA has gradually become a more important design tool over the years. Practical aspects concerning sandwich structures and FEA, weight optimization and evaluations of results, are discussed.

EXPERIENCES FROM USING CARBON FIBER COMPOSITES / SANDWICH CONSTRUCTION IN THE SWEDISH NAVY

Anders LonnoFMV, Swedish Defence Material Administration, S-1 15 88, Stockholm Sweden

The paper discusses the experiences gained from 3 different naval craft projects, Corvette Visby, Combat Craft 90E and the hovercraft KA MI0X, All 3 crafts are constructed in a sandwich design based on carbon fibre / vinylester skins and PVC-foam. The paper will focus on topics such as material characterization and material properties, design and design loads, producability and quality assurance. In addition when it comes to the combat craft 90 E, performance and repair experiences will be presented.

COMPARATIVE STUDY OF THE FATIGUE PERFORMANCE OF SANDWICH STRUCTURES

S.D Clark and R.A. Shenoi

Department of Ship Science, University of Southampton, U.K.

The object of this paper is to report on a series of fatigue tests carried out on a range of different sandwich material configurations in order to evaluate their fatigue performance. The skin materials chosen are glass fibres with either epoxy, vinylester or phenolic resins, whilst the core materials considered are crosslinked PVC foam, balsa and a syntactic phenolic core. The fatigue data is then compared with a more conventional glass/epoxy PVC core construction and differences in behaviour outlined. The fatigue data is presented on master curves pertaining to both the skin tensile/compression and the core shear failure mode. These master curves can be used as part of a fatigue design approach in order to improve fatigue life predictions of structural sandwich components

SUBSTRUCTURE AND YIELD DESIGN IN SANDWICH BEAMS

Deborah Weissman-Berman

Research Scientist, NOVA Southeastern University, Dania, FL, USA

The secondary yield region defines the limit of the design regime. In continuous core materials, sub-structure affects the secondary compressive stress through a non-dimensional modulus of residual stiffness, a , which must be taken into account to analyze the response to load. Elasto-visco-plastic effects at secondary yield are determined when the core is modeled as a granular or a capillary soil. Compressive tests define the maximum stress, the elastic curve and location of the interlocking shear regime. These values define 'a ' which characterizes the bounded core, forms a part of the characteristic length of the sandwich defining the elastic curve, and is defined by the compressive stress at secondary yield. Predicted values of 'a ' are compared to test data, the results plotted showing regimes of acceptable stress and factors of safety.

NEW RESCUE AND SAFETY SYSTEMS AT SEA WITH THE SES-LIFE RESCUE BOAT

S E Sorelius,

Ing Firma S E Sorelius, Stockholm, Sweden

SAVE EVERY SOUL, must be the goal in all serious research and development of life-saving appliances at sea. In order to arrive at the best possible solutions , the starting point for any research, development and design should be based on functional requirements and not strictly on technical regulations. SOLAS regulations have to be observed with some reservation. An abandonment system on board a ship is very complex and comprises, lifeboats and rescue boats, life rafts, launching and embarkations appliances, lifejackets...

CHALLENGES FOR TEAMING UP SANDWICH TECHNOLOGY AND BUSINESS SUCCESS IN RAIL TRANPORTATION

L. den Haan and G.Reif

Alusuisse Airex Composites

The growing number of projects shows an increasing acceptance of sandwich structures in rail vehicles. To achieve business success is a challenge for both the rail vehicle manufacturer and the sandwich subassembly supplier. The basis for success is a close partnership, the willingness to share information openly and a detailed understanding of each others capabilities and business. For the sandwich supplier, this means building up new capabilities and competences, which go far beyond the mere manufacturing and delivery of individual parts.

ANALYSIS OF SANDWICH STRUCTURES FOR RAILWAY VEHICLES

Per Wennhage and Karl-Axel Olsson

Department of Aeronautics, Division of Lightweight Structures, Royal Institute of Technology, Stockholm.

Some general conclusions are drawn from the analysis of a generic railway car body of sandwich design. The design criterion is that the first natural frequency was required to be above a certain limit. The sensitivity of the weight to some design parameters is investigated. The second part of the article is a study where sound reduction index is used as constraints in minimization of a structural sandwich panel's surface weight. This should be considered as an example of how acoustic requirements can be taken into account as well as the strength and stiffness requirements.

DIMENSIONING OF WOUND SANDWICH TRAMWAY CARRIAGE

D. Huybrechts

Schindler Technik AG, 9423 Altenrhein, Switzerland

An innovative production technology based on winding process and sandwich technology was developed for railway carriages. The paper gives a short introduction about the manufacturing process, the materials used and the design principles. The focus is on the specialities of deformation analysis and strength proof concerned with this new technology. Whereas the primary important FE based stiffness analysis can be carried out with a high level of certainty, there remain some uncertainties for the strength proof to overcome only with an adequate safety factor concept.

DESIGN AND STRUCTURAL TESTING OF THE GRP SANDWICH FRONT CAB MODULE OF THE GERMAN BR424-426 SUBURBAIN TRAIN

A. Starlinger, H. Waldeck, T. de Kalbermatten

Alusuisse Road & Rail Ltd,, Buckhauserstr, 11, CH-8048 Zuerich, Switzerland

The front cab module of the new German suburban train BR424-426 was designed as a GRP sandwich structure. The structure had to withstand all loadings specified by UIC standards. The compressive loading of 300 kN applied in the longitudinal direction directly under the frame of the front window represented the most severe load case for the front cab design. Nonlinear finite element analyses taking into account contact conditions and viscoelastic adhesives have shown that the GRP sandwich structure is able to withstand all the UIC load cases without failure. In a structural test performed at the test facility of DUEWAG Uardingen was even removed to determine the ultimate failure load.

STRENGTH TESTING UNDER WHEEL LOADING FOR PRE CURVED ALL STEEL SANDWICH PANELS WITH COMPOSITE COATINGS

P. KujalaShip Laboratory, Helsinki University of' Technology

The paper discusses the strength of an all-steel sandwich panel under wheel loading when the precurved surface is coated with various types of composites to level the surface for loading purposes. The panel is planned to be applied as a bottom floor on the cargo carrying railway wagon carrying mainly paper rolls from paper mill to harbour. The surface coatings are tested in laboratory by simulating the wheel loading on the panels during the planned life-time of the railway wagon. The relative characteristics of the used coatings are discussed and recommendations for practical applications are given.

BUCKLING AND WRINKLING OF SANDWICH COLUMNS WITH DIFFERENT FACES

H-R Meyer-PeyningProf. Dr.-Ing., ETH Zurich, Institut for Lightweight Structures and Ropeways, CH8092 Zurich

An analytical method is presented which allows to study the local and global instability of multi-layered asymmetric sandwich beams with arbitrary layer thicknesses. The method accounts for material inplane orthotropy, transverse shear elasticity, Poisson's ratio effects and lateral compressibility of each layer. The results are compared with test results on asymmetric sandwich specimens subjected to controlled shortening ,and with the result of Hoff’s formula. The method is extended to include plasticity effects within the faces and to include consideration of harmonic initial imperfections.

EFFECTS OF IN-PLANE STIFFNESS ON THE WRINKLING LOAD OF SANDWICH CONSTRUCTIONS

Walter K Vonach and Franz G Rammerstorfer

Institute for Lightweight Structures and Aerospace Engineering. Vienna University of Technology, Vienna, Austria

A refined analytical calculation is presented for wrinkling of thick sandwich constructions with isotropic face layers and orthotropic cores. This approach leads to a single explicit equation for the critical wrinkling load in an asymptotic sense, taking into account in-plane deformations of the core. The results have been verified by a numerical model and show that, when dealing with highly orthotropic cores (eg honeycomb) the wrinkling loads and wrinkling patterns can strongly depend on the in-plane stiffness of the core. Therefore, the classical wrinkling formulae can lead to significant errors when used in connection with highly orthotropic cores. For extremely small values of the in-plane stiffness, the wrinkling load decreases to the load given by the Winkler foundation model even for very thick cores.

INACCURACIES AND VALIDITY OF SOME SIMPLIFIED MODELS IN THE THEORY OF SANDWICH STRUCTURES

Y. Frostig

Associate Professor of Structures Engineering, Technion, Israel Institute of Technology, Haifa, Israel

The inaccuracies and the validity of some important simplified models in the theory of sandwich structures with incompressible and compressible (transversely flexible) core are presented. The simplified models reviewed for incompressible core include the splitted rigidity approach with and without the local bending rigidity of the skins and additional model that assumes that the section plane of the core remain vertical after deformations thus inducing inplane displacements in the skins in addition to bending. The inaccuracies involved in the basic model, in its assumptions and in especially in the definition of the boundary conditions are presented analytically and numerically. The validity and the inefficiencies of these models are determined through comparisons with a rigorous model (OSBT) based on a variational approach. In case of a compressible core the one and two parameters elastic foundation models along with a superposition approach are reviewed and their inefficiencies and inaccuracies when compared with the closed-form high-order theory solutions. The results for a typical cantilever case loaded at its free edge by a concentrated load are presented. The governing equations and the appropriate boundary conditions have been rederived to clarify the ambiguity involved in the definition of the he's of the various models. Recommendations on when where to use the simplified models are drawn.

SAINT-VENANT EDGE EFFECTS FOR SANDWICH STRUCTURES

C.O. Horgan

Department of Civil Engineering, University of Virginia

This paper reviews recent results on Saint-Venant decay lengths for self-equilibrated edge loads in symmetric sandwich structures. In linear elasticity, Saint-Venant's principle is used to show that self-equilibrated loads generate local stress effects that decay away from the loaded end of a structure. For homogeneous isotropic linear elastic materials this is well documented. As is described in the present paper, material inhomogeneity and anisotropy significantly affect the practical application of Saint-Venant's principle to sandwich structures. The results are of fundamental importance to sandwich construction technology.

INFLUENCE OF BOUNDARY EFFECTS OF VORTEX-TYPE ON BENDING OF SANDWICH PLATES

V. R. Skvortsov

State Marine Technical University of St-Petersberg, Russia

Two types of transverse deformation of sandwich plates are known: usual combination of bending torsion with shear and deflectionless shear-torsion of vortex-type. Although the latter is ignored by a number of mathematical models, its influence on a plate behaviour can be considerable. In the paper, main general features of deformation of vortex-type are analysed using different 2-D and 3-D formulations. Through several examples for various shape, loading and boundary conditions, its influence on deflections and stresses is demonstrated.

ANALYSIS OF SANDWICH PANELS WITH MULTIPLE SITE-DAMAGE

H. Razi, B. Sergeev, S. Shakarayev and E. Madenci

Stress Methods and Allowables, Boeing Commercial Airplanes, Seattle, Washington 98124, U.S.A

Hail impaction may cause multiple-site damage to sandwich panels used as a part of control surfaces and is therefore a major maintenance and repair concern for the airlines. A strength analysis, of the damaged sandwich panels is essential to predicting the influence of the multi-site damage, which is necessary for establishing allowable damage limits. The location of the damage sites in relation to each other and their size influence the stress field significantly. This study presents an analytical method to determine the stress distribution in sandwich panels with arbitrarily located damage that is elliptical or circular in shape. The validity of this method is established by comparison against the three-dimensional finite element models of. sandwich panels with multiple damage zones.

MOTION OF A LAMINATED SHELL EMBEDDED IN AN ELASTIC MEDIUM

N.A. Lavrov, and E.E. Pavlovskaya

Institute for Problems of Mechanical Engineering of Russian Academy of Sciences

Motion of a thin-walled layered inclusion interacting with a plane harmonic wave is under consideration. The incident wave length is comparable to the large linear size of the inclusion. The layers are parallel with the median surface of the inclusion. Materials of the layers and the surrounding medium (isotropic, homogeneous and linearly elastic) differ in mass density and Young's modulus. Three-dimensional integral equations of elastodynamics are written out for all interacting media and then are asymptotically simplified. A system of integral equations (of reduced dimension) suitable for numerical solution is derived on the basis of asymptotic analysis. Motion of 3-layered circular plate is the example.

INTEGRAL EQUATION SOLUTION FOR A CRACKED SANDWICH LAYER

Efstathios E. Theotokoglu

Department of Engineering Science, Section of Mechanics, Technical University of Athens, GR- 15773 Athens

This paper presents the general solution of an arbitrary system of cracks of any configuration and geometry in a sandwich layer. The solution in terms of complex potentials is given by integrals over the cracks with integrands expressed in terms of Green's functions and an unknown complex density function. The problem reduced to the Solution of a singular integral equation for the complex density function. Numerical results are presented for the stress intensity factors in the case of a single straight crack.

A COMPARATIVE LCA STUDY ON A BOAT STRUCTURE

A.Hedlund-Astrom and K.A. Olsson

Department of Aeronautics, Division of Lightweight Structures, Royal Institute of Technology, Stockholm.

Transportations of people and products are fundamental in our society. When developing towards a sustainable future the use of fossil fuel must decrease due to the environmental effects from emissions of CO2. In harmony with this the vehicles must be more efficient with lower weight and effective engines. By performing a life cycle assessment, LCA, the environmental effects are shown. In this study a comparative LCA is made for a coast guard boat. The structural materials compared are aluminium and GRP-sandwich. In this first part of the study the results from a screening LCA were raw material production, manufacturing of structure and usage are presented.

USE OF ASYMMETRIC SANDWICH CONSTRUCTION TO MINIMIZE BENDING STRESSES

J.R. Vinson and Alexander Dell

Department of Mechanical Engineering, University of Delaware.

In shells, bending stresses in addition to the membrane stresses exist in the vicinity of each structural discontinuity (such as at edge supports. rings. stringers, holes, etc.) and each load discontinuity. This region is the "bending boundary layer". In sandwich shells, mid-plane asymmetry can be employed to minimize these bendine stresses. Governing equations for the mid-plane asymmetric sandwich shell subjected to axially symmetric loads are derived herein and solved. The solution involves a mid-plane assymetry factor j , defined herein such that for any asymmetric sandwich construction, -1 < j < 1. Therefore, perturbation solutions are easily obtained using the solutions for the symmetric shell.

HYBRID STAINLESS STEEL ASSEMBLIES FOR WEIGHT REDUCTION AND PERFORMANCE

Roland N_G Gustafsson, AB Volvo, 40508 Sweden

A new way to create structural stiffness from section properties rather than material properties.

NEW DESIGNS OF SANDWICH ENGINE FOUNDATIONS

Leping Feng, Anders Nilsson and Leif Kari

The Marcus Wallenberg Laboratory for Sound and Vibration Research

Based on the consideration of weight and of vibration generation of a marine engine foundation, two new designs are suggested. Numerical estimation of transmission loss is made by using a simplified transmission line model. Acoustic properties of the new designs are thoroughly compared experimentally with that of the standard design. Applicability of the test results is investigated. Three parameters are used: vibration level at the excitation point; vibration level at the reference point; and averaged vibration level at the bottom plate. It is found that the new designs have much better acoustic properties, and are much lighter, than the standard one.

REDESIGN OF REFRIGERATED TRUCK FLOORS BY MEANS OFOPTIMIZATION

J. Rasmussen and P. Staelens

Institute of Mechanical Engineering, Aalborg University, Denmark

This paper presents the modelling, analysis and optimization of floors of refrigerated trucks with the purpose of reducing weight and cost. The objective is to show how optimization and systematic finite element analysis can shorten the development time when a change of material selection from polyurethane to styrofoam leads to a completely different structural behaviour. The modelling and analysis turns out to be problematic and great care must be taken when interpreting results. The optimization process allows quick identification of possible design improvements and shortens the development time significantly compared to a traditional trial-and-error process, but it does not eliminate the need for engineering creativity and fundamental mechanical understanding of the structural behaviour.

BEHAVIOUR PREDICTION OF A DEBONDING IN A SANDWICH MATERIAL

P. Thevenet, R. Grappein, D. Carronnier, D. Guedra-Degeorge

Material Department, Aerospatiale-CCR Louis B1eriot, Suresnes, France

This paper describes the work done by Aerospatiale on the behaviour prediction of debonding in sandwich materials under loading. The method of propagation prediction is presented. A simulation is performed on a basic sandwich structure including a circular debonding. By the way of the method, the propagation load and direction are predicted. Some compression tests are performed on this structure in order to verify and validate the numerical results.

ACTUATION AND SENSING OF SOFT CORE SANDWICH PLATES WITH A BUILT-IN ADAPTIVE LAYER

H. Abramovich and H-R. Meyer-Piening

Faculty of Aerospace Engineering, Technion, I.I.T., 32000 Haifa, Israel

The present work presents experimental studies on soft core sandwich planar plates with a built-in adaptive layer. This adaptive layer consists of an aluminum plate equipped with piezoelectric ceramic transducers (PZT) bonded in pairs on its two faces. The PZT patches can sense deflections using the direct piezoelectric effect (producing charge under the application of stress) and can be also used as actuators to induce deflections to the structure, using the converse piezoelectric effect (inducing shear deformations to the host structure by its stretching or shrinkage under the application of voltage). This configuration of the sandwich has the main advantage of protecting the brittle ceramic transducer by placing them inside the core. The outside sandwich faces remain then unobstructed.

A HIGHER ORDER THEORY FOR THE NON-LINEAR ANALYSIS OF THICK SANDWICH BEAMS

Hans-G Reimardes and Thomas Schermann

Institut fur Leichtbau, Rheinisch-Westfalische Technische Hochschule Aachen, Germany

A higher order theory for the analysis of sandwich beams is presented. Within the theory applied here, the resulting transverse shear stress distribution remains constant and the transverse normal stress distribution is linear over the core thickness, whereas the displacement field is non-linear. For the face sheets a beam bending theory expanded by nonlinear terms, taking the equilibrium equations of the deformed structure into account, is used. The established system of differential equations of first order is solved numerically leading to the transfer matrix of a sandwich beam section. A sandwich beam under four point bending is studied and the solution is compared to results obtained by the Finite Element method (here MARC).

ANALYSIS OF COMPOSITE SANDWICH PANELS VIA A TRIANGULAR SHELL ELEMENT BASED ON HIGHER-ORDER THEORY

A. Bartit, E. Madenci and A. Tessler

Department of Aerospace and Mechanical Engineering, The University of Arizona, Tucson, AZ 85721, U.S.A.

This study presents a higher-order triangular shell element to investigate the response of sandwich composite panels experiencing large displacements and rotations. Based on equivalent single-layer assumptions, the in-plane and transverse displacement components are expressed as linear and quadratic expansions through the panel thickness. The element formulation utilizes the principle of virtual work in conjunction with the co-rotational form of the updated Lagrangian description of motion. The basis for the finite element formulation is a three node triangular flat shell element, leading to the complete stress and strain fields. The accuracy of this nonlinear higher order shell element is established via a series of numerical comparisons with the benchmark solutions obtained using conventional three-dimensional solid elements.

BENEFITS AND CONSEQUENCES OF NON-LINEAR EFFECTS IN SANDWICH PANEL-FIELDS

Martin Hildebrand & Jycki Riihentaus

VTT ManufacturingTechnology, P.O. Box 1705, FIN - 02044 VTT, Finland

The potential benefits of non-linear behaviour in sandwich panel fields are shown. These are either an increase in load carrying capacity or a reduction in structural weight. The results are based on finite element analyses performed on a variety of stiffened panel fields under both lateral load and a combination of lateral and in-plane loads. The range of validity of linear analysis methods is discussed and the results of the panel-field analyses are compared with these obtained with corresponding single panel analyses. The consequences of non-linear effects are discussed. Allowing for and exploiting non-linear behaviour requires to perform a variety of tasks with an increased level of knowledge.

OVERALL NONLINEAR BEHAVIOUR OF SINGLY-CURVED SANDWICH PANELS: THE CASE OF GENERAL BOUNDARY CONDITIONS

E Bozhevolnaya, A Kildegaardand V Svortsov

Aalborg University, Denmark

An overall behaviour of shallow sandwich panel with arbitrary initial profile and general boundary conditions under arbitrary load is discussed. A mathematical model based on the Reissner-Mindlin plate theory is developed, and the set of governing equations is derived. Implicit nonlinear and explicit linear solutions are obtained for a uniformly loaded panel with uniform curvature and similar boundary restraints. Applicability and efficiency of the presented model are demonstrated with numerical Simulations.

FINITE ELEMENT STRESS AND FRACTURE ANALYSIS OF SANDWICH AND MULTILAYERED COMPOSITE STRUCTURES

A. Borovkov and Yu. Misnik

Laboratory of Computational Mechanics, Department of Mechanics and Control Processes, St. Petersburg State Technical University,

New general algorithm for the finite element (FE) fracture analysis of sandwich and multidirectional laminated composite structure based on the energy methods of linear fracture mechanics (LFM) is presented. The modification of the virtual crack closure integral technique introduced by Chow and Atluri is used for the computation of the critical fracture parameters. To formulate the algorithm the sequential heterogenization method and locality principle in the mechanics of composites are used. The results of FE analysis of delamination problems with detailed microstructure in the crack tip zone are presented. For this purpose new 3D hyper-large FE models of multidirectional laminates are analysed.

FINITE ELEMENT STRESS AND VIBRATION ANALYSIS OF SANDWICH AND MULTILAYERED BEAMS

A. Borovkov, 1. Avdeev and A. Atemyev

Laboratory of Computational Mechanics, Department of Mechanics and Control Processes, St. Petersburg State Technical University

In present work, the stress and vibration finite element analysis of laminated and sandwich beams is performed. Finite element algorithms and procedures integrated into the original FEA programme system and based on the first-order shear deformation theory (FSDT), third order theory of Reddy (TSDT-R) and third-order theory of Kant (TSDY-K) and Lanczos method for solving of the eigen problem are developed. Several numerical examples of bending and free vibration of sandwich beams with various material and geometry properties are solved. The comparative analysis of results obtained by the considered models and solutions of the 2D problems of the heterogeneous anisotropic elasticity is fulfilled.