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Showing papers on "Sandwich-structured composite published in 2006"


Journal ArticleDOI
TL;DR: In this paper, lattice truss topologies with open cell structures were evaluated for structural load support in light-weight sandwich panel structures, and three classes of periodic cellular metals can be fabricated from a wide variety of structural alloys.
Abstract: Periodic cellular metals with honeycomb and corrugated topologies are widely used for the cores of light weight sandwich panel structures. Honeycombs have closed cell pores and are well suited for thermal protection while also providing efficient load support. Corrugated core structures provide less efficient and highly anisotropic load support, but enable cross flow heat exchange opportunities because their pores are continuous in one direction. Recent advances in topology design and fabrication have led to the emergence of lattice truss structures with open cell structures. These three classes of periodic cellular metals can now be fabricated from a wide variety of structural alloys. Many topologies are found to provide adequate stiffness and strength for structural load support when configured as the cores of sandwich panels. Sandwich panels with core relative densities of 2-10% and cell sizes in the millimetre range are being assessed for use as multifunctional structures. The open, three-dimensional interconnected pore networks of lattice truss topologies provide opportunities for simultaneously supporting high stresses while also enabling cross flow heat exchange. These highly compressible structures also provide opportunities for the mitigation of high intensity dynamic loads created by impacts and shock waves in air or water. By filling the voids with polymers and hard ceramics, these structures have also been found to offer significant resistance to penetration by projectiles.

716 citations


Journal ArticleDOI
TL;DR: In this paper, a numerical model of bird-strike tests on double sandwich panels made from AlSi7Mg0.5 aluminium foam core and aluminium AA2024 T3 cover plates was developed with the finite element program LS-DYNA.

214 citations


Journal ArticleDOI
TL;DR: In this paper, a low-speed impact of a one-dimensional sandwich panel by a rigid cylindrical projectile is considered, where the core of the sandwich panel is functionally graded such that the density and hence its stiffness vary through the thickness.

157 citations


Journal ArticleDOI
TL;DR: In this paper, a triaxial weaving of wires to create ideal trusses has been presented, and the failure mechanisms of the sandwich panels are analyzed, and also benefits and shortcomings of each approach with respect to mechanical performance and production are discussed.

129 citations


Journal ArticleDOI
TL;DR: In this article, a set of test results obtained from quasi-static measurements of the out-of-plane tension, shear and compression properties of novel X-Cor and K-Cor™ flat sandwich panels are presented.
Abstract: The paper presents the first complete set of test results obtained from quasi-static measurements of the out-of-plane tension, shear and compression properties of novel X-Cor™ and K-Cor™ flat sandwich panels. The cured panels were composed of 0.75-mm-thick quasi-isotropic IM7/8552 skins, separated by 12.7-mm-thick Rohacell® foam core containing 0.51 mm diameter carbon fibre pins (Z-Fiber®), arranged in a truss pattern at pin angle of either 22 or 30° to the vertical. To obtain a suitable baseline comparison, the equivalent set of properties was measured for Nomex honeycomb core panels sandwiched by the same composite skins. The novel Z-pinned cores are found to exhibit higher specific stiffness than conventional sandwich cores, but lower strength.

127 citations


Journal ArticleDOI
TL;DR: In this paper, the results of visual, ultrasonic C-Scan and laser shearography impact damage assessment and determination of sandwich panels, which were cut out from sandwich skins of this developmental wing were evaluated as the most suitable method for that purpose.
Abstract: The new all-composite wing for semi-aerobatic sport and training aircraft is being developed in the Czech aircraft industry. The typical outer composite structure of this wing is sandwich with carbon skins in combination with honeycomb. This new composite structure is designed in accordance with CS-23 airworthiness requirements. The NDI techniques for reliable detecting of manufacture or in-service defects (disbonding, defects from impact, etc.) are therefore, necessary. This paper compares the results of visual, ultrasonic C-Scan and laser shearography impact damage assessment and determination of sandwich panels, which were cut out from sandwich skins of this developmental wing. Considering the reliability, simplicity and rapidity of each technique and with the digital indicator measurement as a base, the laser shearography is evaluated as the most suitable method for that purpose.

122 citations


Journal ArticleDOI
TL;DR: In this article, an experimental and computational study of the bending response of steel sandwich panels with corrugated cores in both transverse and longitudinal loading orientations has been performed, and it has been shown that when failure initiation is controlled by yielding, appreciable hardening follows the initial nonlinearity.

111 citations


Journal ArticleDOI
TL;DR: In this article, a new approach to active cooling performance is presented, and the results show that some geometric parameters can be fixed without much detriment in thermal performance, while optimal core densities are typically 25-50%, near-optimal results can be obtained with densities as low as 10%.

106 citations


Journal ArticleDOI
TL;DR: In this paper, the thermal conductivity and warmth-keeping properties of thick plywood-faced sandwich panels with low-density fiberboard, which were developed as wood-based structural insulation materials for walls and floors, are comprehensively clarified.
Abstract: Thermal insulation and warmth-keeping properties of thick plywood-faced sandwich panels with low-density fiberboard (plywood-faced sandwich, PSW), which were developed as wood-based structural insulation materials for walls and floors, are comprehensively clarified. The properties focused on were thermal conductivity (λ), thermal resistance (R), and thermal diffusivity (D). The results for PSW panels were compared with those for commercial wood-based boards, solid wood, and commercial insulators. The λ values were measured for PSW panels and their core and face elements. As a result, the composite theory of λ was found to be appropriate for PSW composites, because the calculated/experimental λ ratios were approximately 90%. The λ values for PSW panels with densities of 340 kg/m3 (PSW350) and 410kg/m3 (PSW400) were 0.070 and 0.077W/mK, respectively. The R values for PSW350 and PSW400 were 1.4 and 1.2m2K/W, and the D values were 0.00050 and 0.00046m2/h, respectively. Consequently, the PSW provided thermal insulation properties superior to those of the boards and in terms of warmth-keeping properties were greatly advantageous over the insulators. These advantages were due to the moderate densities of PSW panels. The PSW panel with sufficient thickness showed remarkably improved thermal resistance compared with those of the boards.

105 citations


Journal ArticleDOI
TL;DR: In this paper, a finite element numerical algorithm for the simulation of two-dimensional problems of heat transfer with phase change is validated, comparing the numerical results with the experimental ones deriving from tests carried out on two different kinds of PCM containing sandwich panels.

105 citations


Journal ArticleDOI
TL;DR: In this article, an experimental investigation to study the ultimate strength behavior of precast concrete sandwich panels (PCSPs) with steel truss shear connectors is reported, where the role of the shear truss connectors in transferring load from the outer wythe (layer) to the inner and ensuring composite behavior was also observed.

Journal ArticleDOI
TL;DR: In this paper, the experimental identification and validation of a non-parametric probabilistic approach allowing model uncertainties and data uncertainties to be taken into account in the numerical model developed to predict low and medium-frequency dynamics of structures is performed for a composite sandwich panel representing a complex dynamical system.

Journal ArticleDOI
TL;DR: In this article, a 2D model of truss-cored sandwich panels has been developed using homogenization techniques, which form the basis of a two-dimensional (2D) single-layer sandwich model.

Proceedings ArticleDOI
01 May 2006
TL;DR: In this paper, a preliminary design process of an integral thermal protection system (ITPS) has been presented, where an optimization problem was formulated as part of the design process with mass per unit area (MPUA) as the objective function and different functions of the ITPS as constraints.
Abstract: A preliminary design process of an integral thermal protection system (ITPS) has been presented. Unlike the conventional TPS, the ITPS has both thermal protection as well as load bearing capabilities. The objective of this research work is to establish procedures and identify issues in the design of an ITPS. Corrugated-core sandwich construction has been chosen as a candidate structure for this design problem. An optimization problem was formulated as part of the design process with mass per unit area of the ITPS as the objective function and different functions of the ITPS as constraints. The optimization problem was solved by developing response surface approximations to represent the constraints. Response surface approximations were obtained from finite element (FE) analyses, which include transient heat transfer analyses and buckling analyses. A Matlab code (ITPS Optimizer) has been developed for generating the response surfaces, which has the capability to carry out hundreds of FE analyses, automatically, in conjunction with ABAQUS. Accurate response surface approximations could be obtained for the peak temperatures of the ITPS structure. It was found that response surface approximations for the smallest buckling eigen value of the whole structure were inaccurate. Therefore, the buckling modes were separated and similar buckling modes were grouped together. One response surface approximation was obtained for the smallest buckling eigen value of each group. The preliminary design process for the ITPS generates a design with areal density of approximately 10 lb/ft. Even though the ITPS has much higher load bearing capabilities, it is still on the heavier side when compared to conventional TPS (typical weight 2 lb/ft). New design changes have been proposed as part of the future work to make the ITPS lighter than the current design.

Journal ArticleDOI
TL;DR: In this paper, the impact force during low speed impact on circular sandwich panels was calculated using finite element analysis using ABAQUS to calculate impact damage on sandwich panels and the dependence of damage on both structural parameters and impact variables was investigated.

Journal ArticleDOI
TL;DR: In this paper, the deformation, penetration, and perforation of composite plates and sandwich panels subjected to quasi-static punch indentation and projectile impact are derived, and a generalized solution methodology for projectile impact is proposed based on three key factors: (i) the contact load duration, (ii) the through-thickness transit time, and (iii) the lateral transit time.
Abstract: Analytical solutions for the deformation, penetration, and perforation of composite plates and sandwich panels subjected to quasi-static punch indentation and projectile impact are derived. Discrete spring-mass models are used to calculate the impact response of the composite plates and sandwich panels. Equivalent load resistance functions are obtained from the quasi-static analysis and adjusted for high strain rate. A generalized solution methodology for projectile impact of composite plates and sandwich panels are then proposed based on three key factors: (i) the contact load duration, (ii) the through-thickness transit time, and (iii) the lateral transit time. A two-dimensional wave propagation model is used to determine the ballistic limits of E-glass/polyester panels and GLARE fiber-metal laminates, and predicted values are found to be within 20 and 13% of the experimental results, respectively. A quasi-static impact model is used to predict the ballistic limit for E-glass/epoxy-aluminum honeycomb sa...

Journal ArticleDOI
TL;DR: In this paper, the effect of the transverse compressibility of the core on the transient dynamic response of structural sandwich panels under rapid loading conditions is investigated based on a higher-order sandwich shell theory in an effective multilayer formulation.

Journal ArticleDOI
TL;DR: In this paper, an instrumented Hopkinson pressure bar was used as a perforator and at the same time a measuring device for the measurement of piercing force-displacement curves under quasi-static and impact loadings.
Abstract: This paper reports an original inverse perforation tests on foam core sandwich panels under impact loading. The key point is the use of an instrumented Hopkinson pressure bar as a perforator and at the same time a measuring device. It aims at a high quality piercing force record during the whole perforation process, which is a lack of common free-flying projectile - target testing schemes. This new testing arrangement allows for the measurement of piercing force-displacement curves under quasi-static and impact loadings of sandwich samples, which is made of 40 mm AlSi7Mg0.5 Cymat foam cores and 0.8 mm thick 2024 T3 aluminium sheet as top and bottom skins. Compared with quasi-static top skin peak loads (the maximal load before the perforation of top skins) obtained under same geometric and clamping conditions and even in the case that the used foam core (Cymat) and aluminium skin sheet are known and have been confirmed rate insensitive, a significant enhancement under impact loading (25%) of the top skin peak load is found.

Journal ArticleDOI
TL;DR: In this article, a thin layer of a fire resistant paste composed of Geopolymer and hollow glass microspheres was applied to the facings to serve as a protective fire barrier and to improve the fire resistance of the sandwich panels.
Abstract: The study presented in this paper deals with the fire performance of balsa sandwich panels made using inorganic Geopolymer resin and high-strength fiber facings. A thin layer of a fire-resistant paste composed of Geopolymer and hollow glass microspheres was applied to the facings to serve as a protective fire barrier and to improve the fire resistance of the sandwich panels. Using 17 sandwich panel specimens, the primary objective of this program was to establish the minimum amount of fireproofing necessary to satisfy the Federal Aviation Administration (FAA) requirements for heat and smoke release. The influence of this fireproofing insulation on the increase in mass of the panels was also evaluated. The system is simple and inexpensive to manufacture, and a 1.8-mm-thick layer of fireproofing satisfies the FAA requirements for both heat release and smoke emission.

Journal ArticleDOI
TL;DR: In this article, the effect of processing parameters on the peel strength of Nomex honeycomb core/carbon fibre-epoxy prepreg skin sandwich panels, manufactured by vacuum bagging, was investigated.
Abstract: Experimental design has been used to investigate the effect of processing parameters on the peel strength of Nomex honeycomb core/carbon fibre-epoxy prepreg skin sandwich panels, manufactured by vacuum bagging. The four processing parameters considered were: (i) consolidation pressure; (ii) temperature cure cycle; (iii) temperature ramp rate and (iv) vacuum pressure application time. Each parameter was considered at three levels. It was found that (ii) was the dominant parameter. Panels manufactured under the optimum combination of processing parameters gave a mean peel strength more than twice that of the worst panels. Qualitative microscopy has associated the higher peel strengths with larger, regular shaped adhesive fillets between honeycomb cell walls and skin laminate.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the damage characteristics of composite-skinned honeycomb sandwich panels in bending with both hemispherical (HS) and flat-ended (FE) indenters.
Abstract: Damage characteristics of composite-skinned honeycomb sandwich panels in bending are investigated with both hemispherical (HS) and flat-ended (FE) indenters. The thickness of the cross-ply skins va...

Journal ArticleDOI
TL;DR: In this paper, a pin reinforced polymer foam core with carbon fiber face sheets is used to evaluate the collapse properties of X-core composite panels, and explicit experimental observations are used to calibrate analytical energy balance models describing the panel collapse.
Abstract: New fabrication technologies now allow for hybrid sandwich structures, known as X-core, to be manufactured. The X-core panels consist of a pin reinforced polymer foam core with carbon fiber face sheets. Carbon fiber or metallic (Titanium/Steel) pins are inserted into the foam core in the out-of-plane direction and extend from face sheet to face sheet. The through thickness three-point simply supported bending behavior of these panels is used to evaluate the collapse characteristics of the panels. Explicit experimental observations are used to calibrate analytical energy balance models describing the panel collapse as a function of geometry and properties. The mechanical response of X-core sandwich panels is compared to current sandwich materials for material selection.

Journal ArticleDOI
TL;DR: In this article, the elastic-plastic response of sandwich composite beams with a foam core to local static loading is investigated. But the authors focus on a 2D configuration, where a sandwich beam is indented by a steel cylinder across the whole width of the specimen and the ABAQUS finite element package is used to model the indentation response of the beams.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the collapse of a sandwich panel or beam with a square cell honeycomb, and developed a new iterative optimization design method for a square honeycomb sandwich panel and the curves of critical compressive stresses with geometrical parameters.

Book ChapterDOI
TL;DR: In this article, a study devoted to the dynamic response of sandwich panels to underwater and in-air explosions is presented, in the context of a geometrically nonlinear model of sandwich structures featuring anisotropic laminated face sheets and a transversally compressible orthotropic core.

Journal ArticleDOI
Hualin Fan1, Wei Yang1, Bin Wang1, Yang Yan1, Qiang Fu1, Daining Fang1, Zhua Zhuang1 
TL;DR: In this article, an intertwining method was chosen and developed as the best route to make lattice composite materials reinforced by carbon fibers, and a sandwich-weaved sample with a three-dimensional intertwined lattice structure core was found to be best.

Journal ArticleDOI
TL;DR: In this article, an improved fully dynamic higher-order impact theory is developed to analyze the low-velocity impact dynamic of a system which consists of a composite sandwich panel with transversely flexible core and multiple small impactors with small masses.

Journal ArticleDOI
TL;DR: In this paper, the formability of aluminium foam sandwich (AFS) panels was investigated through experiments and numerical simulations, and FEM analyses were developed using a porous material model following the evolution of the material density throughout the forming processes.

Journal ArticleDOI
TL;DR: In this paper, the out-of-plane performance of honeycomb materials for sandwich panels was evaluated. But, the performance was not as good as that of other core materials, such as graphite.
Abstract: Compared to other core materials, honeycomb materials provide impressive mechanical performance for sandwich panels, but with less weight added to the structures. In this article, the out-of-plane ...

Journal ArticleDOI
TL;DR: In this paper, an experimental study of the in-plane compression failure of sandwich panels consisting of glass/epoxy face sheets over a range of PVC foam cores (H45, H100, and H200) and a balsa wood core containing one or two circular or square interfacial debonds is conducted.
Abstract: An experimental study of the in-plane compression failure of sandwich panels consisting of glass/epoxy face sheets over a range of PVC foam cores (H45, H100, and H200) and a balsa wood core containing one or two circular or square interfacial debonds is conducted. For the great majority of the specimens, failure occurred by local buckling of the debonded face sheet followed by rapid debond growth towards the panel edges, perpendicular to the applied load. Panels with the largest debond (10 cm diameter or 9 cm length) displayed some post-buckling strength. Examination of the face and core failure surfaces after total separation showed that the tendency for interface (core/resin) failure increases with increasing core density. It was found that the compression strength strongly decreases with decreasing core stiffness and increasing debond size. The compression strength of panels with H45 core decreased with reduced core thickness. Failure loads for panels with symmetric debonds at both face/core interfaces...