Sandwich Elements Research Articles

The Core of Inner ideal of Real Four Dimensional Lie Algebra With One Dimensional Derived

Suppose that V is any inner ideal of L. The core of V is an inner ideal of L with special requirement. In this paper we prove. If L is a 4-dimension Lie algebra a with 1-dimensional derived , then the core of every inner ideal of L is zero. Moreover L containing a sandwich elements if L' not subset of Z and every element in L is sandwich if L' subset of Z. .

Driving rain tightness and defects of prefabricated concrete sandwich walls with joints, windows and balconies

There have historically been, and still are, problems with water intrusion into new external walls of prefabricated concrete sandwich elements in Sweden to a varying extent. The aim of this study was to obtain documented knowledge and data on driving rain resistance, to provide a basis for improvements and calculations in a common kind of concrete sandwich system with façade components and sealing products. The study included inspections and air pressure difference measurement of façades in the field and driving rain resistance testing of experimental set-ups in a laboratory. Inspection showed that vertical joints between the concrete elements were often significantly too narrow and, at the same time, adhesion loosening of building mastic in these joints was common. TDV-tubes were often incorrectly placed or had a bad incline. Field measurements indicate no pressure equalization, which is also confirmed by lab measurements. Lab results indicated inward leakage at window-wall interface, even without wind pressure, through the TDV-tubes despite a sharp incline, in element joints with a new kind of application of pre-compressed joint sealing tape. The largest leakage flows were of 0.4% of the vertical water flow across a unit width of the façade at the given height.

Sandwich elements and the Richardson property

A restricted Lie algebra L over an algebraically closed field k of characteristic p>0 is said to possess the Richardson property if there exists a finite dimensional faithful restricted L-module V with associated representation ρ:L→gl(V) such that gl(V)=ρ(L)⊕R where R is a subspace of gl(V) such that [ρ(L),R]⊆R. In [31], the author conjectured that if L has the Richardson property with respect to an irreducible restricted L-module V then there exists a reductive algebraic group G over k such that L≅Lie(G) as restricted Lie algebras. In this note we confirm this conjecture under the assumption that p>3. This assumption is needed since our proof relies in a crucial way on the classification of Lie algebras without strong degeneration obtained in [25] for p>5 and in [24] for p=5.

Flexural response of textile-reinforced sandwich slab with modified polymeric core

Concrete sandwich panels are thermally insulative but difficult to erect due to heavy weight and thickness, and also require sufficient clear cover to avoid corrosion. Textile reinforcement is a novel field of research in civil engineering. The size, weight, and cost can be reduced using it as reinforcement in sandwich elements. The past researchers focus on sandwich slabs with polymeric cores which are prompt to delamination. Thus, this study compares the performance of steel mesh, and basalt textile fiber mesh reinforced sandwich slabs with conventional concrete and expanded perlite board as core materials. The sandwich slabs are tested under flexure in four-point bending and validated numerically by considering the non-linear characteristics of the material. The sandwich slabs reinforced with steel and basalt textile fiber mesh have similar load-carrying capacities with higher deflection of basalt textile mesh-reinforced sandwich slabs. The core material plays a major role than the type of reinforcement used. Conventional concrete core sandwich slabs did not show any delamination by enhancing the degree of composite action and mitigated the shear failure without shear connectors than sandwich slabs with expanded perlite cores. However, it affects the major property of the sandwich panel due to its density. Using the cast in-situ method in manufacturing sandwich specimens rather than adopting the slab stock method avoids delamination by proper bonding between the layers. Thus, textile-reinforced sandwich slabs have a similar load-carrying capacity as of concrete sandwich panels with steel mesh. The experimental results are validated well with numerical data.

Comparative Study to Assess the Thermal Behaviour of Sandwich Roof Panels with Coconut Fibre as an Alternative Core Material to Polyurethane

Sandwich panels (modular panels) promote optimal solutions to some major issues prevailing in the construction industry such as increased energy consumption by building elements, excessive disposal of constructional waste and unproductive time spent during construction. Hence, the inclination towards sandwich elements has been increased vastly deviating from conventional building construction materials and methods. However, the potentiality of using locally available natural materials for the development of sandwich panels is a salient sustainable approach that needs to be addressed. This study evaluates the current and potential materials used in modular panels and key properties of sandwich panels including mechanical, thermal insulation, and sound insulation properties. Moreover, various test methods followed, and standards specified to investigate the mechanical, thermal and acoustic insulation properties are also discussed. The possibility of using coconut fibre as a locally available natural alternative core material to polyurethane core of sandwich panels has been evaluated using simulations based on the material properties obtained from literature. The study identifies coconut fibre as a potential alternative core material for sandwich roof panels as it reflects nearly similar thermal behaviour to polyurethane.

A review on the various factors influencing the structural behaviour of TRC sandwich elements

This review article discusses the structural performance of Textile Reinforced Concrete (TRC) sandwich structures consisting of two outer TRC faces and a rigid core insulation. Sandwich structures offer advantages such as lightweight construction and thermal insulation. Hence, the application of the non-corrosive TRC as the facings of sandwich panels helps in reducing the overall thickness and weight of the panels by replacing the reinforced concrete faces and eliminating the thick concrete cover. The strength, stiffness and load-carrying capacity of TRC sandwich panels are governed by several factors such as thickness of the face, density of the core material, reinforcement ratio, the use of shear stiffeners, etc. In this review article, the influence of various parameters such as face thickness, type of textile, number of textile layers, core thickness and core density are addressed. The effect of shear connectors on enhancing the composite behaviour of TRC sandwich panels is also discussed.

Multimodal NDT monitoring of TRC sandwich under bending and early detection of interlaminar debonding

Textile Reinforced Cementitious (TRC) sandwich composites provide a load-bearing, noncorrosive, lightweight, and durable alternative for steel-reinforced sandwich elements, and/or traditional steel-reinforced concrete. However, the composite nature of the material and slender nature of the facings render the fracture behavior complex. Insufficient interlaminar bond can cause premature debonding, substantially reducing the loadbearing capacity of the composite. Non-Destructive Testing (NDT) techniques seem the obvious choice to monitor the damage progression of the material without affecting, nor compromising the behavior of the composite, and predict their service life. In this study, TRC sandwich composites, subjected to quasistatic four-point bending, are monitored with three NDTs. Digital Image Correlation (DIC) allows to measure the surface strains and displacements. MMW Spectrometry, used for the first time in bending damage monitoring, allowed to detect damage such as cracking, or debonding, while Acoustic Emission (AE) allowed to localize and characterize internal cracking. In order to simulate premature debonding, the bond between the tensile TRC facing and the insulation, in the central zone, where the bending moment is maximum, was artificially destroyed. Results show that a weak interlaminar bond reduced the ultimate load of the composite by more than 50%. Additionally, DIC, AE and MMW Spectrometry proved useful to monitor and characterize damage. Multimodal data gathered from the multimodal NDTs showed to be complementary. DIC allowed to interpret AE and MMW Spectrometry data from a surface viewpoint, while AE parameters permit predictions at low load conditions, and detect internal cracking. For instance, the AE behavior at early load stage (less than 15% of the maximum load) of the TRC sandwich with destroyed bond showed significant differences than for the reference TRC sandwich. Specifically, it showed higher RA values, and lower AF than the reference TRC sandwich, suggesting more shear related early activity for, promoted by the damaged bond. Results were corroborated with DIC, while MMW Spectrometry seemed to follow closely the level of damage of TRC sandwich composites under quasi-static four-point bending. EWGAE 35, Ljubljana, Slovenia, 13th – 16th Sep. www.ewg

Renovating Modern Heritage

The post-war building stock is increasingly being transformed. Even at objects protected as listed heritage, renovation usually results in a high degree of material exchange and replacement. This is especially the case in regard to historic curtain wall constructions. Based on the case study of the Commerzbank High-rise and original planning documents by Gartner, the paper focuses on the applied strategy of disassembling and reassembling the curtained aluminium sandwich elements, and the resulting upgrading of the original façade with a newly installed interlayer for insulation. The paper discusses the possible transfer of this strategy, which largely depended on the existing high quality of the aluminium components, their corrosion-resistant properties and low weight. The case study of the former Commerzbank High-rise indicates that a long-term preservation of post-war modern building stock can be achieved without wholesale replacement of original building components. The reuse of existing materials and components represents a promising approach.

Face/core disbond fatigue growth in honeycomb cored aircraft sandwich elements under mixed mode flatwise tension loading

Disbond damage growth in honeycomb cored sandwich structures due to static and fatigue mixed mode loading is investigated numerically and experimentally. A two dimensional finite element model was generated using core homogenization and the Crack Surface Displacement Extrapolation mode separation method, integrated into a fracture mechanics based analysis sub-routine to predict face/core interface fatigue crack propagation. The Cycle Jump technique was furthermore applied to accelerate fatigue analysis. Mixed mode fatigue characterization testing was conducted using Double Cantilever Beam specimens loaded with Uneven Bending Moments, generating a relationship between crack propagation rates and energy release rate amplitudes as a modified Paris Law, measured at three mode-mixity phase angles. The measured Paris laws were subsequently used as input data for the numerical fatigue model. The numerical model was validated against CFRP/Nomex® Sandwich Tearing Test specimen tests with a propagating face/core interface crack yielding varying mode-mixities. The results from the validation showed good agreement between numerical predictions and experimental measurements.

A sandwich in thin lie algebras

AbstractA thin Lie algebra is a Lie algebra $L$, graded over the positive integers, with its first homogeneous component $L_1$ of dimension two and generating $L$, and such that each non-zero ideal of $L$ lies between consecutive terms of its lower central series. All homogeneous components of a thin Lie algebra have dimension one or two, and the two-dimensional components are called diamonds. Suppose the second diamond of $L$ (that is, the next diamond past $L_1$) occurs in degree $k$. We prove that if $k>5$, then $[Lyy]=0$ for some non-zero element $y$ of $L_1$. In characteristic different from two this means $y$ is a sandwich element of $L$. We discuss the relevance of this fact in connection with an important theorem of Premet on sandwich elements in modular Lie algebras.

Mechanical and fatigue behaviour of Sandwich elements with ABS core cells and GFRP plies, as function of cellular geometry and process parameters

The present work aim is to fully apply the potential of FDM (Fused Deposition Modelling) technology with economic printing machine, in order to create performant ABS cores, to be subsequently used as shaped moulds for sandwich plate assembly with GFRP skins, representing simple prototypes to validate production concept and its structural behaviour. The further task of this study is to empirically optimize the geometry of the core as function of required thickness and technological building parameters, in order to achieve light and mechanically performing structures with extremely reduced costs. After compression experimental tests on core cell geometries, fatigue tests under bending are also executed on reinforced GFRP plates in order to validate best compromise between ABS core design and GFRP laminated skin properties and stiffness requirement, highlighting influence of ABS wire performances as deposited in the form of beam-based lattice geometry. In addition, the authors employ the digital image correlation technique to perform the strain and displacement field of lattice structures and sandwich interfaces.

Solar thermal component activation

Wall and roof components made of steel sandwich elements are firmly established in industrial and commercial construction. They are cost-effective and characterized by excellent physical properties. Here, hybrid approaches from heating- and cooling ceiling construction were examined for the solar thermal activation of sandwich elements. Besides the implementation of the solar components, the connection to and the optimization of the system technology was focused. In addition, alternative piping materials were investigated numerically and experimentally. The performance as well as the static and thermo-hydraulic behavior of the new active components were simulatively and experimentally examined, and the economic viability of the variants was also checked. With the newly developed solar sandwich elements, an overall energy concept was developed with connection variants to the building services system, control and storage technology. Steel sandwich elements with mineral fiber core are well suited for the hidden integration of component parts such as pipe registers and heat conducting plates. The functionality of the component has been proven, the implementation of heat exchanger leads to considerable heat gains. In combination with a brine-to-water heat pump system, the solar panel can provide for a more sustainable operation and a significant size reduction of the geothermal source.

Glass‐rigid foam composite for innovative concrete sandwich elements

AbstractIn building envelopes, sandwich elements with facings made of glass currently require either adhesives or mechanical connectors. The avoidance of any connectors seems to be favorable in terms of resource and energy savings both in production and in building envelopes. The present studies are part of the development of a glass‐rigid foam‐concrete sandwich element without additional adhesives and mechanical connectors. This paper reports on the structural bond behavior between polyurethane rigid foam and float glass with different surfaces with or without applying a bonding agent. Tensile bond and shear tests show, that a sandblasted toughened glass surface results in cohesive failure of the insulation layer. The two production‐related surfaces of float glass are defined as atmosphere and tin side. Both surfaces offer an adhesive failure between the insulation layer and glass. Test specimens of glass and insulation layer without bonding agent show no significant differences between the atmosphere and the tin side. Overall, the test specimens with bonding agents achieve higher levels of adhesive tensile bond and shear strength. Light and electron microscopic studies of fractured surfaces show, that the bonding agent has a significant influence on the wetting and pore formation of the liquid polyurethane.

Bond between concrete and rigid foam in precast concrete sandwich construction

AbstractIn precast concrete sandwich construction mechanical connectors are used to transfer loads between the two concrete shells. Omitting these connectors seems economically interesting for realizing novel sandwich elements with lightweight facings made of textile‐reinforced concrete or other materials. Then, the adhesion between the isolating layer and the cover layers becomes the decisive parameter. In order to evaluate the basic influence of surface texture and type of concrete on the bond strength, an experimental study including different rigid foams and ordinary performance concrete (OPC) as well as ultra‐high performance concrete (UHPC) was carried out. The results of 120 tensile bond tests and 30 shear tests on concrete‐rigid foam composites show that technically relevant bond strengths can be achieved by pouring the concrete onto the rigid foam. For OPC, the tensile bond strength is 50% higher than the minimum value required for external thermal insulation composite systems without mechanical connectors. For UHPC significantly higher bond strengths are obtained, which can be attributed to a better micromechanical interlock. In some cases, the strength of the composite was limited by the strength of the foam. The results are valuable for identifying promising rigid foam‐concrete configurations.

Energized activate sandwich elements with mineral fibre core

Steel ConstructionVolume 13, Issue 3 p. 207-207 Editor's Recommendations Energized activate sandwich elements with mineral fibre core First published: 17 August 2020 https://doi.org/10.1002/stco.202070305 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume13, Issue3August 2020Pages 207-207 RelatedInformation

Verification of the Structural Performance of Textile Reinforced Reactive Powder Concrete Sandwich Facade Elements

As a part of the SESBE (Smart Elements for Sustainable Building Envelopes) project, non-load bearing sandwich elements were developed with Textile Reinforced Reactive Powder Concrete (TRRPC) for outer and inner facings, Foam Concrete (FC) for the insulating core and Glass Fiber Reinforced Polymer (GFRP) continuous connectors. The structural performance of the developed elements was verified at various levels by means of a thorough experimental program coupled with numerical analysis. Experiments were conducted on individual materials (i.e., tensile and compressive tests), composites (i.e., uniaxial tensile, flexural and pull-out tests), as well as components (i.e., local anchorage failure, shear, flexural and wind loading tests). The experimentally yielded material properties were used as input for the developed models to verify the findings of various component tests and to allow for further material development. In this paper, the component tests related to local anchorage failure and wind loading are presented and coupled to a structural model of the sandwich element. The validated structural model provided a greater understanding of the physical mechanisms governing the element’s structural behavior and its structural performance under various dead and wind load cases. Lastly, the performance of the sandwich elements, in terms of composite action, was shown to be greatly correlated to the properties of the GFRP connectors, such as stiffness and strength.

Fatigue Behaviour of Textile Reinforced Cementitious Composites and Their Application in Sandwich Elements

Using large lightweight insulating sandwich panels with cement composite faces offers great possibilities for the renovation of existing dwellings. During their lifetime, these panels are subjected to wind loading, which is equivalent to a repeated loading. To guarantee the structural performance of these panels during their entire lifetime, it is necessary to quantify the impact of these loading conditions on the long term. The fatigue behaviour was, therefore, examined in this paper both at the material level of the faces and at the element level as well. plain textile reinforced cementitious composite (TRC) specimens were subjected to 100,000 loading cycles by means of a uniaxial tensile test, while sandwich beams were loaded 100.000 times with a four-point bending test. Results show that the residual behaviour is strongly dependent on the occurrence of cracks. The formation of cracks leads to a reduction of the initial stiffness. The ultimate strength is only affected in a minor way by the preloading history.

THz spectroscopy for inspection and evaluation of internal structure of sandwich samples

Purpose The purpose of this paper is to discuss the application of THz spectroscopy for the inspection and evaluation of the internal structure of complex samples with honeycomb fillers. Design/methodology/approach Three complex samples with honeycomb fillers are investigated using THz spectrometer in order to determine the applicability of chosen non-destructive method for the analysis of internal structure of structural components. The first analysed sample has aluminium honeycomb filler with some cells filled with water. The aim of the analysis is to distinguish empty and full cells. The other two sandwich samples are made of different non-metallic components and for them the possibility of THz spectroscopy application is analysed. Findings The empty and full cells in metal honeycomb filler were easily distinguished due to different absorption coefficients of electromagnetic waves in THz range for air and water. It was especially visible for frequency domain. The THz spectroscopy was able to inspect the non-metallic samples internal structures and distinguish skins (with layers), honeycomb fillers and adhesive layers between them. It was also possible to detect, localise and determine the size of a local damage of honeycomb walls due to impact influence. Originality/value The present study is an original research work. There are very limited literature papers which present analyses of internal structures of sandwich elements using THz spectroscopy and investigate utility of the method for mechanical damage and contamination (water) detection and localisation.

Composite Behaviour of Textile Reinforced Reactive Powder Concrete Sandwich Fa\xe7ade Elements

Within the EC funded project smart elements for sustainable building envelopes, carbon textile reinforcement was incorporated into reactive powder concrete, namely textile reinforced reactive powder concrete (TRRPC), to additionally improve the post-cracking behaviour of the cementitious matrix. This high-performance composite material was included as outer and inner façade panels in prefabricated and non-load bearing sandwich elements along with low density foamed concrete (FC) and glass fibre reinforced polymer continuous connecting devices. Experiments and finite element analysis (FEA) were applied to characterize the structural performance of the developed sandwich elements. The mechanical behaviour of the individual materials, components and large-scale elements were quantified. Four-point bending tests were performed on large-scale TRRPC-FC sandwich element beams to quantify the flexural capacity, level of composite action, resulting deformation, crack propagation and failure mechanisms. Optical measurements based on digital image correlation were taken simultaneously to enable a detailed analysis of the underlying composite action. The structural behaviour of the developed elements was found to be highly dependent on the stiffness and strength of the connectors to ensure composite action between the two TRRPC panels. As for the FEA, the applied modelling approach was found to accurately describe the stiffness of the sandwich elements at lower load levels, while describing the stiffness in a conservative manner after the occurrence of connector failure mechanisms.

Influence of constraints on the effective inplane extensional properties of honeycomb core

This study is focused on the influence of constraints on the extensional in-plane modulus of isolated honeycomb core (HC) and honeycomb core sandwich elements. Such constraints develop when the core is bonded to stiff face sheets. Finite element analysis (FEA) is conducted on unconstrained and constrained HC core under inplane loading. FEA results for the extensional in-plane modulus and Poisson ratios of isolated unconstrained HC core are in good agreement with estimates from the classical Gibson-Ashby analysis. Such analysis reveals that the isolated core has very low extensional modulus (Ex) and large Poisson ratio νxy. Constraints imposed on the lateral deformation of the core substantially increased the effective axial stiffness. In the limit of equal biaxial strains, the increase was close to a factor of 1000. The FEA results for the effective modulus of the HC core sandwich element are in good agreement with predictions from classical laminated plate theory.