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Inspeção por ressonância magnética nuclear de painéis-sanduíche compósitos de grau aeronáutico; Nuclear magnetic resonance inspection of aeronautical grade composite sandwich panels

Portela, Alexandre Machado Aguiar
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 17/11/2011 PT
Relevância na Pesquisa
66.81%
O presente trabalho objetivou desenvolver e implementar, em escala laboratorial, uma rotina experimental com base em Imageamento por Ressonância Magnética Nuclear (IRMN) de modo a verificar seu potencial como metodologia não-destrutiva aplicável à inspeção quali- e quantitativa de água e hidrocarbonetos líquidos aprisionados no interior de células de núcleos-colméia utilizados na confecção de painéis-sanduíche compósitos estruturais de grau aeronáutico. Tentativas foram também realizadas no sentido de se observarem e caracterizarem danos por amassamento de núcleos-colméia, assim como de se detectar a presença de resina polimérica na forma sólida, visando, desta feita, verificar o uso do IRMN na inspeção de componentes previamente reparados e/ou contendo excesso de resina por falha do processo de manufatura. Concluiu-se que IRMN é uma poderosa ferramenta para a detecção e a quantificação de líquidos puros e compostos, ricos em hidrogênio, contidos nas células de núcleos de amostras extraídas de painéis-sanduíche compósitos. O potencial do IRMN na identificação, e, portanto, na discriminação entre os diversos fluidos se mostrou bastante promissor, desde que se empreguem ferramentas de processamento e análise computadorizada de imagens a partir de programas computacionais de reconhecimento de padrões via redes neurais artificiais e/ou sistemas com base em conhecimento. A técnica de IRMN utilizada neste estudo não permitiu a captura de imagens de resina polimérica sólida...

Development of reinforced composite sandwich panels based on 3D fabrics

Fangueiro, Raúl; Velosa, J. C.; Hattum, F. W. J. van; Soutinho, F.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em //2010 ENG
Relevância na Pesquisa
57.08%
relative new type of sandwich material was investigated, based on 3D knitted sandwich fabric preforms. Due to the integrally interlacement of both sandwich-fabric the skins by the connection yarns – core debonding resistance of panels and structures based on the perform is very high. [1]. In this work the mechanical performance of sandwich composite panels based on sandwich knitted fabrics is presented and discussed. Different 3D sandwich knitted fabric performs have been produced varying the thickness and the interlacement pattern. Composite panels using these performs have been produced using vacuum infusion technique. Panel thicknesses of 8, 15 and 25 mm, using two resin types – polyester and epoxy – have been produced. Materials thus obtained have been tested in tensile, bending and impact. The results obtained are presented, discussed and compared to models. Various samples of 3D sandwich spacer fabrics using vacuum infusion process have been produced in order to study the impregnation process. The dimensional properties investigated for non-impregnated core structures include cross-threads density, areal mass, yarns linear density, etc. Results obtained show that the mechanical performances vary according to the type of 3D knitted sandwich perform and the type of resin used.

Fibre Reinforced Polymer (FRP) connectors for Steel Fibre Reinforced Self-Compacting Concrete (SFRSCC) sandwich panels

Lameiras, Rodrigo; Valente, Isabel; Barros, Joaquim A. O.; Azenha, Miguel; Ferreira, Patrícia Isabel da Silva
Fonte: CICE 2012 6th International Conference on FRP Composites in Civil Engineering Publicador: CICE 2012 6th International Conference on FRP Composites in Civil Engineering
Tipo: Conferência ou Objeto de Conferência
Publicado em //2012 ENG
Relevância na Pesquisa
56.81%
Insulated sandwich wall panels are frequently composed of external concrete layers, mechanically connected through metallic connectors, such as trusses. Due to their high thermal conductivity, these connectors generally cause thermal bridges on the building envelope. In view of this problem, an innovative system is proposed where FRP connectors are used together with a thermal insulation layer. Steel Fibre Reinforced Self-Compacting Concrete (SFRSCC) wythes are also used to obtain panels that are both technically and economically advantageous. However, to present day there is no experimental data on the mechanical behaviour of the suggested connections. In this research, an experimental study is performed to characterize different types of FRP-SFRSCC connections under pull-out tests. Shear connection behaviour under monotonic loading is evaluated with slip controlled tests. Embedded and adhesively bonded connection solutions between SFRSCC layers and FRP connectors are studied.

Conception of sandwich structural panels comprising thin walled steel fibre reinforced self-compacting concrete (SFRSCC) and fibre reinforced polymer (FRP) connectors

Lameiras, Rodrigo; Barros, Joaquim A. O.; Azenha, Miguel; Valente, Isabel
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em //2012 ENG
Relevância na Pesquisa
56.96%
In this paper, an innovative thermally efficient sandwich structural panel is proposed for the structural walls of a pre-fabricated modular housing system. Traditionally, sandwich concrete panels consist of conventional reinforced concrete wythes as external layers, polystyrene foam as core material and steel connectors. However, steel connectors are known to cause thermal bridges on the building envelope and possibly condensation and mould problems. Furthermore, the possibilities for thickness reduction/optimization of conventionally reinforced concrete layers are frequently limited by minimum cover requirements. To overcome these issues, the proposed sandwich panel comprises Fibre Reinforced Polymer (FRP) connectors and two thin layers of Steel Fibre Reinforced SelfCompacting Concrete (SFRSCC). This paper presents the basic conception of the proposed building system together with preliminary parametric numerical analyses to define the arrangement and geometry of the elements that constitute the sandwich panels. Finally, the feasibility of using the proposed connector and SFRSCC on the external wythes is experimentally investigated through a series of pull-out tests where failure modes and load capacity of the connections are analysed.

Flexural and shear behaviour of precast sandwich slabs comprising thin walled steel fibre reinforced self-compacting concrete

Sousa, Christoph Fernandes; Barros, Joaquim A. O.; Azenha, Miguel; Lameiras, Rodrigo
Fonte: RILEM Publicador: RILEM
Tipo: Conferência ou Objeto de Conferência
Publicado em //2013 ENG
Relevância na Pesquisa
56.81%
Publicado em "Rheology and processing of construction materials", ISBN 978-2-35158-137-7; Insulated sandwich panels are often composed of external concrete layers, mechanically connected through metallic elements, such as trusses. Due to their high thermal conductivity, metallic connectors tend to cause thermal bridges on the building envelope. In view of this problem, an innovative solution for sandwich slabs is proposed within the framework of a pre-fabricated modular housing system. The referred slabs are based on a sandwich solution composed by two thin layers of Steel Fibre Reinforced Self-Compacting Concrete (SFRSCC) that are connected by thin perforated plates of Glass Fibre Reinforced Polymer (GFRP), used together with a thermal insulation core-layer. The bottom concrete layer is reinforced with conventional steel rebars and steel fibres, whereas the upper one does not have conventional reinforcement. This paper presents a preliminary experimental program aiming to assess the flexural and shear behaviour of this type of sandwich panel solution. The obtained results confirm the feasibility of the proposed sandwich slab system, revealing its capacity in terms of load carrying capacity and ductility performance. In addition...

Aplicação de técnicas BIM à construção modular com Painéis Sandwich

Silva, Pedro Daniel Moreira da
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Trabalho de Conclusão de Curso
Publicado em //2012 POR
Relevância na Pesquisa
57.01%
Dissertação de mestrado integrado em Engenharia Civil; A construção modular é um processo construtivo que permite a conceção em ambiente controlado de módulos habitacionais que podem ser transportado para qualquer local e instalado em menor tempo, comparativamente aos processos tradicionais, introduzindo novas vantagens económicas e construtivas. A utilização de painéis sandwich em betão estrutural permite a conceção de módulos que combinam os benefícios integrados da utilização do isolamento para o conforto térmico com o suporte estrutural desempenhado pelas camadas de betão do painel. BIM – Building Information Modeling é uma nova metodologia de projeto apoiado no desenvolvimento de modelos virtuais, que são integrados com as diversas informações e dados funcionais do edifício, que são transacionados entre aplicações BIM através de ficheiros IFC, estimulando a interoperabilidade entre os intervenientes da elaboração de projeto e construção. Neste trabalho pretende-se aferir o nível de interoperabilidade entre aplicações preparadas para o conceito BIM, através da conceção de um caso de estudo que simula as interações entre as equipas de arquitetura e as equipas de especialidades hidráulica e térmica. O modelo de arquitetura foi concebido com o apoio da aplicação ArchiCAD através da modelação paramétrica em GDL dos painéis sandwich. A comunicação entre as aplicações BIM é realizada através da utilização do ficheiro IFC...

Acoustical behavior of hybrid composite sandwich panels

Patinha, Sérgio; Cunha, Fernando Eduardo Macedo; Fangueiro, Raúl; Rana, Sohel; Prego, Fernando
Fonte: Trans Tech Publications Publicador: Trans Tech Publications
Tipo: Artigo de Revista Científica
Publicado em //2015 ENG
Relevância na Pesquisa
67.06%
This paper deals with the characterization of acoustic insulation behaviour of hybrid sandwich composite panels for application in modular house construction. These sandwich panels are a sustainable, light-weight and durable solution, since are based on natural fibers structure impregnated with a thermosetting polymer. In this way, three different types of hybrid composite panels containing polyurethane core and laminated composite skins were produced and analyzed, varying the composition of laminates. The composite laminates of the prototypes were produced using a vacuum infusion technique and were composed of glass and jute fibers, impregnated with a polyester resin. The solutions developed were compared with a standard, composed of plasterboards having different thicknesses and used for thermal and acoustic insulation. Acoustic insulation characterization was performed on specimens with 220x220 mm size in a sound proof acoustic chamber. The tested sandwich panels showed promising results; however, their overall performance was lower as compared to the performance of standard solutions used for comparison. Nevertheless, the specific acoustic insulation performance, i.e. sound reduction per unit mass of material for the developed sandwich panels was significantly higher as compared to the standard materials...

Impact properties of aluminium - glass fiber reinforced plastics sandwich panels

Periasamy,Mathivanan; Manickam,Balakrishnan; Hariharasubramanian,Krishnan
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2012 EN
Relevância na Pesquisa
66.93%
Aluminium - glass fiber reinforced plastics (GFRP) sandwich panels are hybrid laminates consisting of GFRP bonded with thin aluminum sheets on either side. Such sandwich materials are increasingly used in airplane and automobile structures. Laminates with varying aluminium thickness fractions, fiber volume fractions and orientation in the layers of GFRP were fabricated by hand lay up method and evaluated for their impact performance by conducting drop weight tests under low velocity impacts. The impact energy required for initiating a crack in the outer aluminium layer as well as the energy required for perforation was recorded. The impact load-time history was also recorded to understand the failure behavior. The damage depth and the damage area were measured to evaluate the impact resistance. Optical photography and scanning electron micrographs were taken to visualize the crack and the damage zone. The bidirectional cross-ply hybrid laminate (CPHL) has been found to exhibit better impact performance and damage resistance than the unidirectional hybrid laminate (UDHL). Increase in aluminium thickness fraction (Al tf) and fiber volume fraction (Vf) resulted in an increase in the impact energy required for cracking and perforation. On an overall basis...

Response of Metallic Pyramidal Lattice Core Sandwich Panels to High Intensity Impulsive Loading in Air

Hutchinson, John W.; Dharmasena, Kumar P.; Williams, Keith; Xue, Zhenyu; Wadley, Haydn N. G.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
67.08%
Small scale explosive loading of sandwich panels with low relative density pyramidal lattice cores has been used to study the large scale bending and fracture response of a model sandwich panel system in which the core has little stretch resistance. The panels were made from a ductile stainless steel and the practical consequence of reducing the sandwich panel face sheet thickness to induce a recently predicted beneficial fluid–structure interaction (FSI) effect was investigated. The panel responses are compared to those of monolithic solid plates of equivalent areal density. The impulse imparted to the panels was varied from 1.5 to 7.6 kPa s by changing the standoff distance between the center of a spherical explosive charge and the front face of the panels. A decoupled finite element model has been used to computationally investigate the dynamic response of the panels. It predicts panel deformations well and is used to identify the deformation time sequence and the face sheet and core failure mechanisms. The study shows that efforts to use thin face sheets to exploit FSI benefits are constrained by dynamic fracture of the front face and that this failure mode is in part a consequence of the high strength of the inertially stabilized trusses. Even though the pyramidal lattice core offers little in-plane stretch resistance...

Mechanical behavior of dip-brazed aluminum sandwich panels

Hohmann, Brian P. (Brian Patrick)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 161 leaves
ENG
Relevância na Pesquisa
47.04%
An experimental study was carried out to determine the mechanical behavior of sandwich panels containing cellular cores of varying shape. Compression and four point bend tests were performed on sandwich panels with square and triangular honeycomb cores. These honeycombs were made of perforated aluminum sheet of repeating diamond and hexagonal patterns. The sandwich panel assemblies were joined via dip brazing. Defects were introduced into some panels to quantify the effect on strength and stiffness. Hybrid sandwich panels, consisting of foam material in the void spaces of the square and triangular cells were evaluated for the effect on the defect tolerance of the structures. The results showed that sandwich panels with diamond shaped cores had compressive strengths approximately four times greater than hexagonal shaped cores. In four point bending the diamond cores were approximately twice as stiff as cores made from hexagonal patterned sheet. The introduction of defects lowered strength by about 30% for diamond cores in compression, and about 15% for hexagonal cores. In four point bending this strength reduction was not as significant due to shear stresses damaging periodicity at a faster rate than in compression.; (cont.) The use of foam within the cells resulted in higher absolute peak compression and flexure loads...

Estudo de painéis sanduíches de poliéster reforçado com fibras vegetais para aplicação como forro; Sandwich panels of polyester reinforced with natural fibers for application as ceiling

Ferreira, Monise Ramos da Silva
Fonte: Universidade Federal de Uberlândia Publicador: Universidade Federal de Uberlândia
Tipo: Dissertação
POR
Relevância na Pesquisa
57.06%
O objetivo deste trabalho é produzir e caracterizar mecanicamente painéis sanduíches para uso como forro em edificações, a partir de compósitos de poliéster reforçado com fibras vegetais de rami e bucha vegetal, e núcleos constituídos de bucha vegetal impregnada de resina poliéster e poliestireno expandido - EPS. Os compósitos foram produzidos com diferentes teores de fibras, caracterizados mecanicamente à tração e testados numericamente como constituintes das faces do painel sanduíche. O EPS e a bucha vegetal foram estudados como componentes de núcleo dos painéis. O desempenho mecânico à flexão dos painéis foi testado experimentalmente e pelo Método dos Elementos Finitos. A simulação numérica foi usada também como ferramenta de análises qualitativas para o pré-dimensionamento dos componentes dos painéis, com variação de materiais, teores de volumes de fibras dos compósitos e espessuras de faces e núcleos. As faces dos painéis sanduíches foram constituídas com o compósito de matriz de poliéster reforçada com o tecido bidirecional de fios de rami e combinadas com os núcleos de EPS e bucha vegetal. Os resultados obtidos permitiram concluir que é viável a utilização dos painéis sanduíches estudados para uso como forro. ________________________________________________________________________________ ABSTRACT; The purpose of the work is to produce and characterize mechanically sandwich panels to using as ceiling in buildings. The faces of the panels were made of composites reinforced by ramie and sponge gourd fibers...

FLEXURAL BEHAVIOUR OF SANDWICH PANELS COMPOSED OF POLYURETHANE CORE AND GFRP SKINS AND RIBS

SHARAF, TAREK
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
66.92%
This study addresses the flexural performance of sandwich panels composed of a polyurethane foam core and glass fibre-reinforced polymer (GFRP) skins. Panels with and without GFRP ribs connecting the skins have been studied. While the motivation of the study was to develop new insulated cladding panels for buildings, most of the work and findings are also applicable to other potential applications such as flooring, roofing and light-weight decking. The study comprises experimental, numerical, and analytical investigations. The experimental program included three phases. Phase I is a comprehensive material testing program of the polyurethane core and GFRP skins and ribs. In Phase II, six medium size (2500x660x78 mm) panels with different rib configurations were tested in one-way bending. It was shown that flexural strength and stiffness have increased by 50 to 150%, depending on the rib configuration, compared to a panel without ribs. In Phase III, two large-scale (9150x2440x78 mm) panels, representing a cladding system envisioned to be used in the field, were tested under a realistic air pressure and discrete loads, respectively. The deflection under service wind load did not exceed span/360, while the ultimate pressure was about 2.6 times the maximum factored wind pressure in Canada. A numerical study using finite element analysis (FEA) was carried out. The FEA model accounted for the significant material nonlinearities...

Short- and long-term performance of compressed earth blocks and sandwich panels with natural skins

Mak, KENNETH
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
56.81%
A drastic increase in environmental awareness has increased demand for renewable materials, energy efficient design and low embodied energy. Two technologies that purport to address this demand are Compressed Earth Blocks (CEB) and Structural Insulated Panels (SIP). CEBs, a form of earthen masonry, can be a cost-effective, locally produced material that provides high thermal capacity with low environmental impact. There is increasing interest in using the blocks in cold climates. However, CEBs are limited by manufacturing controls and susceptibility to water damage. In this study, various combinations of cement and lime stabilizers were tested with metakaolin, a pozzolan, and Plasticure, a water repellent, to determine the compressive strength when CEBs are dry and fully saturated at unconditioned and freeze-thaw conditioned states. Results showed that the most beneficial additive for improving wet-state capacity was Plasticure. Blocks manufactured with 10% cement and Plasticure yielded the best performance, with a dry unconfined strength of 10.23±0.81 MPa and an 11.6% reduction in strength when wet. When exposed to freeze-thaw cycling, Plasticure reduced variability in strength reduction from 90.9% to 23.5%, and increased strength retention by up to 74.7%. SIPs are becoming increasingly popular because of their light weight...

Behavior of Sandwich Panels Subjected to Bending Fatigue, Axial Compression Loading and In-Plane Bending

Mathieson, Haley
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
67.19%
This thesis investigates experimentally and analytically the structural performance of sandwich panels composed of glass fibre reinforced polymer (GFRP) skins and a soft polyurethane foam core, with or without thin GFRP ribs connecting skins. The study includes three main components: (a) out-of-plane bending fatigue, (b) axial compression loading, and (c) in-plane bending of sandwich beams. Fatigue studies included 28 specimens and looked into establishing service life (S-N) curves of sandwich panels without ribs, governed by soft core shear failure and also ribbed panels governed by failure at the rib-skin junction. Additionally, the study compared fatigue life curves of sandwich panels loaded under fully reversed bending conditions (R=-1) with panels cyclically loaded in one direction only (R=0) and established the stiffness degradation characteristics throughout their fatigue life. Mathematical models expressing fatigue life and stiffness degradation curves were calibrated and expanded forms for various loading ratios were developed. Approximate fatigue thresholds of 37% and 23% were determined for non-ribbed panels loaded at R=0 and -1, respectively. Digital imaging techniques showed significant shear contribution significantly (90%) to deflections if no ribs used. Axial loading work included 51 specimens and examined the behavior of panels of various lengths (slenderness ratios)...

Connections and Fatigue Behaviour of Precast Concrete Insulated Sandwich Panels

Teixeira, Nathan
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
57.04%
This study investigates two aspects of precast concrete insulated sandwich wall panels, namely mechanical connections and fatigue behaviour. In the first part, flexural tests were performed on panels with various end support conditions, loading orientations, and reinforcement and shear connector materials. Bolted angle connections were used to simulate practical support conditions, while loads were applied in a manner to simulate windward pressure as well as suction. Panels with steel and basalt fibre-reinforced polymer (BFRP) longitudinal reinforcement were tested and compared. Discrete steel and BFRP shear connectors were also used and evaluated. The bolted angle connections provided partial end fixity, thereby increasing the overall strength and stiffness relative to identical panels simply supported by rollers during testing. In all cases the bolted connections succeeded in developing the full strength of the sandwich panels. Panels with steel reinforcement failed due to rupturing of flexural reinforcement, while a panel with BFRP reinforcement failed due to rupturing of shear connectors and crushing of concrete in one wythe. Panels loaded in the direction of wind pressure achieved higher peak loads than identical panels loaded to simulate suction. An analytical model accounting for material nonlinearity...

Behaviour of Partially Composite Precast Concrete Sandwich Panels under Flexural and Axial Loads

Tomlinson, DOUGLAS
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
56.96%
Precast concrete sandwich panels are commonly used on building exteriors. They are typically composed of two concrete wythes that surround rigid insulation. They are advantageous as they provide both structural and thermal resistance. The structural response of sandwich panels is heavily influenced by shear connectors that link the wythes together. This thesis presents a study on partially composite non-prestressed precast concrete wall panels. Nine flexure tests were conducted on a wall design incorporating ‘floating’ concrete studs and Glass Fibre Reinforced Polymer (GFRP) connectors. The studs encapsulate and stiffen the connectors, reducing shear deformations. Ultimate loads increased from 58 to 80% that of a composite section as the connectors’ reinforcement ratio increased from 2.6 to 9.8%. This design was optimized by reinforcing the studs and integrating them with the structural wythe; new connectors composed of angled steel or Basalt-FRP (BFRP) were used. The load-slip response of the new connector design was studied through 38 double shear push-through tests using various connector diameters and insertion angles. Larger connectors were stronger but more likely to pull out. Seven flexure tests were conducted on the new wall design reinforced with different combinations of steel and BFRP connectors and reinforcement. Composite action varied from 50 to 90% depending on connector and reinforcement material. Following this study...

Deformation and Fracture of Impulsively Loaded Sandwich Panels

Wadley, Haydn N. G.; Børvik, Tore; Olovsson, Lars; Wetzel, John J.; Dharmasena, Kumar P.; Hopperstad, Odd Sture; Deshpande, Vikram; Hutchinson, John W.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
67.08%
Light metal sandwich panel structures with cellular cores have attracted interest for multifunctional applications which exploit their high bend strength and impact energy absorption. This concept has been explored here using a model 6061-T6 aluminum alloy system fabricated by friction stir weld joining extruded sandwich panels with a triangular corrugated core. Micro-hardness and miniature tensile coupon testing revealed that friction stir welding reduced the strength and ductility in the welds and a narrow heat affected zone on either side of the weld by approximately 30%. Square, edge clamped sandwich panels and solid plates of equal mass per unit area were subjected to localized impulsive loading by the impact of explosively accelerated, water saturated, sand shells. The hydrodynamic load and impulse applied by the sand were gradually increased by reducing the stand-off distance between the test charge and panel surfaces. The sandwich panels suffered global bending and stretching, and localized core crushing. As the pressure applied by the sand increased, face sheet fracture by a combination of tensile stretching and shear-off occurred first at the two clamped edges of the panels that were parallel with the corrugation and weld direction. The plane of these fractures always lay within the heat affected zone of the longitudinal welds. For the most intensively loaded panels additional cracks occurred at the other clamped boundaries and in the center of the panel. To investigate the dynamic deformation and fracture processes...

Improved high order free­ vibration analysis of thick double curved sandwich panels with transversely flexible cores

Fard,K. Malekzadeh; Livani,M.; Ghasemi,Faramarz Ashenai
Fonte: Associação Brasileira de Ciências Mecânicas Publicador: Associação Brasileira de Ciências Mecânicas
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2014 EN
Relevância na Pesquisa
56.86%
This paper dealt with free vibration analysis of thick double curved composite sandwich panels with simply supported or fully clamped boundary conditions based on a new improved higher order sandwich panel theory. The formulation used the first order shear deformation theory for composite face sheets and polynomial description for the displacement field in the core layer which was based on the displacement field of Frostig's second model. The fully dynamic effects of the core layer and face sheets were also considered in this study. Using the Hamilton's principle, the governing equations were derived. Moreover, effects of some important parameters like that of boundary conditions, thickness ratio of the core to panel, radii curvatures and composite lay-up sequences were investigated on free vibration response of the panel. The results were validated by those published in the literature and with the FE results obtained by ABAQUS software. It was shown that thicker panels with a thicker core provided greater resistance to resonant vibrations. Also, effect of increasing the core thickness in general was significant decreased fundamental natural frequency values.

The quasi-static and dynamic responses of metallic sandwich structures

St-Pierre, Luc
Fonte: University of Cambridge; Department of Engineering Publicador: University of Cambridge; Department of Engineering
Tipo: Thesis; doctoral; PhD
EN
Relevância na Pesquisa
47.05%
Lattice materials are used as the core of sandwich panels to construct light and strong structures. This thesis focuses on metallic sandwich structures and has two main objectives: (i) explore how a surface treatment can improve the strength of a lattice material and (ii) investigate the collapse response of two competing prismatic sandwich cores employed in ship hulls. First, the finite element method is used to examine the effect of carburisation and strain hardening upon the compressive response of a pyramidal lattice made from hollow tubes or solid struts. The carburisation surface treatment increases the yield strength of the material, but its effects on pyramidal lattices are not known. Here, it is demonstrated that carburisation increases the plastic buckling strength of the lattice and reduces the slenderness ratio at which the transition from plastic to elastic buckling occurs. The predictions also showed that strain hardening increases the compressive strength of stocky lattices with a slenderness ratio inferior to ten, but without affecting the collapse mode of the lattice. Second, the quasi-static three-point bending responses of simply supported and clamped sandwich beams with a corrugated core or a Y-frame core are compared via experiments and finite element simulations. The role of the face-sheets is assessed by considering beams with (i) front-and-back faces present and (ii) front face present...

The dynamic indentation response of sandwich panels with a corrugated or Y-frame core

St-Pierre, L.; Fleck, N. A.; Deshpande, V. S.
Fonte: Elsevier Publicador: Elsevier
Tipo: Article; accepted version
EN
Relevância na Pesquisa
56.81%
This is the accepted manuscript of a paper publishing in the International Journal of Mechanical Sciences (L St-Pierre, NA Fleck, VS Deshpande, International Journal of Mechanical Sciences 2015, 92, 279?289); The dynamic indentation response of stainless steel sandwich panels with a corrugated core or a Y-frame core has been explored using the finite element method to gain insight into the potential of the cores to mitigate against collisions over a wide range of impact velocities pertinent to land and sea-borne vehicles. Back-supported sandwich panels were impacted on the front face by a flat-bottomed or a circular punch at constant velocity ranging from quasi-static loading to 100 m/s. At velocities below 10 m/s the forces on the front and back faces are equal but inertia stabilisation raises the peak load above its quasi-static value. This strength elevation is greater for the corrugated core than for the Y-frame core, and more pronounced for the flat-bottomed punch than for the circular punch. For velocities greater than 10 m/s, the indentation force applied to the front face exceeds the force transmitted to the back face due to plastic-shock effects. In this regime, the force transmitted to the back face by the Y-frame core is markedly less than for the corrugated core...