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Castings are near-net-shape components that are almost always machined to produce the final product. Dimensional variation is driven by casting geometry, dimensional accuracy of mold and core boxes, variation in the mold and core material properties, and casting process. This work examines the shrink behavior of stepped tubular castings with varying wall thicknesses. Dimensional shrink magnitudes are related to processing factors (core type, resin content, and knock-out time) and geometric factors (section size, inner/outer diameter, location relative to parting line) using a full-factorial design of experiment. Shrink factors, a scaling number used in building tooling to obtain the correct size component, are determined as a function of the tube inner and outer diameters as well as length. [ABSTRACT FROM AUTHOR]

Prestressed fit is a new type of composite and metal connection. Compared with the traditional connection, it has the advantages of maintaining fiber continuity, high controllability, and high stability. According to the analytical model, the important parameters of the prestressed joint such as friction coefficient, lap length and winding tension are proposed. The influence of the parameters on the joint performance and stress distribution is studied by the finite element method. The abnormal end phenomenon, the stress relaxation phenomenon, and the stress mutation phenomenon caused by demolding during the joint forming process are explained, and the design of the layering method is optimized. The results show that the end effect makes the relationship between the lap length and the peak torque of the joint nonlinear, and increasing the lap length is beneficial to reduce this effect; before and after demolding, the end stress increases sharply; reducing the winding tension and selecting high modulus core mold materials are conducive to reducing stress relaxation; 90°inner ply angle and ± 45°outer ply angle are ideal layup methods for joint composite materials. [ABSTRACT FROM AUTHOR]

Wind turbine blades are easily struck by lightning, a phenomenon that has attracted more and more attention in recent years. On this subject a large current experiment was conducted on three typical blade sandwich structures to simulate the natural lightning-induced arc effects. The resulting damage to different composite materials has been compared: polyvinyl chloride (PVC) and polyethylene terephthalate (PET) suffered pyrolysis and cracks inside, while the damage to balsa wood was fibers breaking off and large delamination between it and the resin layer, and only a little chemical pyrolysis. To analyze the damage mechanism on sandwich structures of different materials, a finite element method (FEM) model to calculate the temperature and pressure distribution was built, taking into consideration heat transfer and flow expansion due to impulse currents. According to the simulation results, PVC had the most severe temperature and pressure distribution, while PET and balsa wood were in the better condition after the experiments. The temperature distribution results explained clearly why balsa wood suffered much less chemical pyrolysis than PVC. Since balsa wood had better thermal stability than PET, the pyrolysis area of PET was obviously larger than that of balsa wood too. Increasing the volume fraction of solid components of porous materials can efficiently decrease the heat transfer velocity in porous materials. Permeability didn't influence that much. The findings provide support for optimum material selection and design in blade manufacturing. [ABSTRACT FROM AUTHOR]

This paper analyses the lightweight potential of long-fiber-reinforced and local continuous-fiber-reinforced foam injection molded components. Using the LFT-D foam process [7, 13] and breathing mold technology [11, 12], long-glass-fiber-reinforced polypropylene foams were manufactured with a constant weight per unit area and varying density reductions. As the area moment of inertia increases with the wall thickness to the third power, in these investigations small density reductions were sufficient to increase the lexural rigidity by several hundred% compared to a compact reference sample. The fiber length advantage generated by the direct process (injection molding compounding) also meant that even at higher density reductions the ductility was not reduced by the foaming. In order to achieve even better mechanical properties, foam injection molding can be combined with local continuous-fiber reinforcement. To demonstrate the potential, sandwich integral foam components with local continuous-fiber-reinforced facing were produced in-situ in an injection mold and characterized. Fully-consolidated tape blanks and self-reinforced PP fabrics were positioned on both sides of the cavity and heated. Afterwards a gas-loaded melt was injected between them. A short embossing stroke generated sufficient interfacial adhesion between the facing layers and the core material, and the foaming process was initiated by the pressure drop resulting from the precision opening of the injection compression mold. [ABSTRACT FROM AUTHOR]

Vacuum insulation panel (VIP) core materials were successfully fabricated by wet method. The phase composition, microstructure, and thermal conductivity of VIP core materials were investigated. The density of VIP core materials was 176 kg/m3, while the mean thermal conductivity of VIP core materials was about 31 mW/(m · K). The mean thermal conductivities of VIPs were 2.78 mW/(m · K), 2.62 mW/(m · K), 2.47 mW/(m · K), 2.5 mW/(m · K), and 2.4 mW/(m · K), which correlated to VIP core materials that had been dried at 150°C for 30 min, 60 min, 90 min, and at 170°C for 30 min and 60 min, respectively. However, the mean thermal conductivity evaluated for VIPs with core material that had not been dried was 3.0 mW/(m · K). The thermal conductivity of VIPs with core material that had been dried reached a maximum on the third day and tended to be a steady value with time, whereas the one with core material that had not been dried recorded a high thermal conductivity value and continued to rise in a fluctuating pattern with time. According to the result of the thermogravimetric curve, drying at 150°C for 60 min showed characteristics of complete drying. In addition, the thermal conductivity of VIPs at this drying condition was low and stable. Theoretical and experimental analysis showed that the optimum drying condition for fiberglass VIP core materials was drying at 150°C for 60 min. [ABSTRACT FROM PUBLISHER]

This article describes an experimental investigation of characterization methods for ductile core materials. Full-field optical strain measurement methods are used to determine the strain distributions in standard testing methods such as block shear and four-point beam testing, particularly for highly ductile cores subjected to large deformations. The results show that the stress and strain fields in both block shear and sandwich beam tests are very different to those assumed by the testing standards. The test methods result in complex post yield states of stress in the core materials, meaning the core shear strength and ultimate shear strain should not be calculated by classical methods in the post yield region. [ABSTRACT FROM AUTHOR]

This paper deals with the loss distribution of a three-phase induction motor (IM) and a BLDC motor considering operating point-of-core material based on the FEA and experiments. In order to increase motor efficiency, a high grade of core material can be used. However, sometimes it decreases or provides no improvement of efficiency. This is due to the fact that high-grade core materials generally have lower saturation flux density and core loss. Therefore, when operation of point-of-core materials is in a high-saturation region with low frequency, there could be no significant improvements or decrease of efficiency. The presented results give guidelines to selecting core materials to improve motor efficiency. [ABSTRACT FROM AUTHOR]

Objectives. This study evaluated the effect of post surface treatment and of storage condition on the bond between resin composite cores (Clearfil Core) and posts of titanium alloy (Fysika), silica-zircon fiber reinforced epoxy resin (SiliciumPost), and zirconia (CosmoPost). Material and Methods. In the experimental groups, the coronal part of each post received sandblasting or tribochemical silicate-coating (CoJet) treatment. The coronal part of each post was embedded in a cylinder of resin composite core material with the aid of a fixation apparatus. After 15 min, the specimen was freed from the mold and stored in de-ionized water. The axial tensile strength (ATS) of posts was determined in a Universal Testing Machine when extracting the posts from the resin composite cores after: 1) 14 d water storage at 37°C, 2) 14 d water storage at 37°C followed by thermal cycling (6,000 cycles between 5°C and 55°C), or 3) 1 year water storage at 37°C. The results were statistically analyzed by three-way factorial ANOVA and Newman-Keuls' multiple range test. Results. The ATS values were generally higher for Fysika posts and SiliciumPost posts than for CosmoPost posts. Surface treatment effectively improved the ATS values of Fysika posts and SiliciumPost posts, but not those of CosmoPost posts. Thermal cycling or long-term water storage had only minimal effect on the ATS values of the posts. Conclusion. Bonding of resin composite cores to the posts depended more on the material of the post and the surface treatment of posts than on the storage condition. [ABSTRACT FROM AUTHOR]

Critical facesheet wrinkling stresses are determined for thin gauge sandwich structure constructed from thick, highly orthotropic, honeycomb-cored materials containing sub-surface damage due to soft-body impact. A closed-form, analytical expression is extended to account for regions of crushed core extending a uniform depth into the core material. The results show that sub-surface core damage can significantly decrease facesheet support, further reducing the critical wrinkling stress computed from classical formulae. The model accounts for shear traction at the core/facesheet interface and provides a means of assessing the fundamental parameters governing the initiation of facesheet wrinkling in initially flat panels constructed from thick orthotropic cores containing sub-surface damage. The results are discussed in terms of the damage tolerance of panels used in aerospace applications. [ABSTRACT FROM AUTHOR]

To achieve high energy absorption under edgewise compression loading, sandwich composites must experience a progressive failure that includes compression failure of the facesheets. This investigation focused on sandwich core design for energy absorption through the use of failure mode maps. Predictive models for global buckling, facesheet wrinkling, and facesheet compression failure were used to construct failure mode maps as a function of sandwich core thickness and density. Predicted failure loads and initial failure modes were found to be in good agreement with results from edgewise compression testing. Sandwich configurations experiencing facesheet compression failure as the initial failure mode were found to produce the highest energy absorption. These results suggest that sandwich composites may be designed for enhanced energy absorption through the proper selection of core materials and geometries. [ABSTRACT FROM AUTHOR]

Abstract: Mixtures of wastes were prepared to improve on the characteristics of the individual ingredients as Technosols, with special attention given to heavy metal extractability. An anaerobic digested sewage sludge and a CaO-treated aerobic sludge were used. A mixture of the two sludges (50:50 DW basis) was also prepared to provide a third type of sludge. The residues were mixed with other types of waste, such as fly ash, Linz-Donowitz slag, foundry sand, shot blasting machine scrap, fettling and barley straw. Extractability of Cu, Cr, Ni, and Zn by 0.01M CaCl2 extraction () was carried out, and leachability of these elements was estimated by acidification of an aqueous suspension of the mixtures with 0.5N acetic acid (Meacetic). The total concentrations of the metals were also determined (MeT). The /MeT ratios for Cu and Ni (means: 4.0% and 3.1%) were higher than those for Cr and Zn (means: 0.07% each). The mean Meacetic/MeT ratios followed the order Ni, Zn, Cu, and Cr (19.5%, 4.1%, 3.7%, and 0.09%, respectively). The results highlight the existence of complex interactions among organic matter solubility, pH and heavy metal extractability. [Copyright &y& Elsevier]

Abstract: In order to enhance structural robustness of microfactory machine elements the foam-composite sandwich structure was introduced. Unidirectional carbon/epoxy prepreg as skin materials and PVC foams as core materials were used to construct the sandwich structures. The existing aluminum column and the column block were replaced by foam-composite sandwich structures with appropriate rib geometries and configurations. The stacking sequences and rib configurations were determined by finite element analyses. The damping capacity was also investigated by vibration tests preparing beam type composite and foam-composite sandwich specimens with various stacking sequences and thickness ratios. The prototype of the column and the column block were fabricated using proper moulds and processes and finally, the system performances such as dynamic robustness and damping capacity were verified by comparison with the existing aluminum system. [Copyright &y& Elsevier]

AbstractThe 2005 Mars Astrobiology Research and Technology Experiment (MARTE) project conducted a simulated 1-month Mars drilling mission in the Río Tinto district, Spain. Dry robotic drilling, core sampling, and biological and geological analytical technologies were collectively tested for the first time for potential use on Mars. Drilling and subsurface sampling and analytical technologies are being explored for Mars because the subsurface is the most likely place to find life on Mars. The objectives of this work are to describe drilling, sampling, and analytical procedures; present the geological analysis of core and borehole material; and examine lessons learned from the drilling simulation. Drilling occurred at an undisclosed location, causing the science team to rely only on mission data for geological and biological interpretations. Core and borehole imaging was used for micromorphological analysis of rock, targeting rock for biological analysis, and making decisions regarding the next day's drilling operations. Drilling reached 606 cm depth into poorly consolidated gossan that allowed only 35 of core recovery and contributed to borehole wall failure during drilling. Core material containing any indication of biology was sampled and analyzed in more detail for its confirmation. Despite the poorly consolidated nature of the subsurface gossan, dry drilling was able to retrieve useful core material for geological and biological analysis. Lessons learned from this drilling simulation can guide the development of dry drilling and subsurface geological and biological analytical technologies for future Mars drilling missions. Astrobiology 8, 1013–1021. [ABSTRACT FROM AUTHOR]

Compression testing of cellular sandwich core materials is often complicated by the presence of edge effects, in which the cells on the outside of the specimen deform at lower stresses than those in the bulk. As a result, minimum specimen length-to-cell-size ratios have been established in the literature for metallic foams. Periodic cellular metals (PCMs) are a recently developed class of materials that have received considerable interest due to their greater architectural efficiency and enhanced mechanical properties compared to conventional metal foams. In this study, edge effects of PCM core materials have been measured in compression using a new test platform which evaluates the properties of the core as a stand-alone material. This approach introduces uniform and periodically rigid boundary conditions to the PCM nodes, resulting in the same inelastic buckling failure mechanism that occurs in reference PCM sandwich panels. Edge effects were comparatively small and samples down to 2 × 2 unit cells were found to be representative of bulk-like cores. [ABSTRACT FROM AUTHOR]

Because of superior speed and productivity, slip forms were extensively utilized as a potential formwork candidate in constructing concrete structures for the past few decades. Typical projects that employ this formwork technique are: Core of high-rise buildings, silos, telecommunication towers, cooling towers, heavy concrete offshore platforms, etc. The research presented in this paper aims at studying slip-form application to cores and silos, assessing its productivity, and determining its appropriate speed as well as auxiliary resource combinations. Simulation models are developed in which the potential control units in a slip-form system are described for cores and silos. Data are collected from several case study projects. A set of charts has been developed to predict productivity considering different stoppages, core cross section area, slipping (jacking) rate, and concrete placing methods. These charts play an essential role in managing slip-form application to cores and silos. Results show that the developed simulation models predict the productivity of case study projects with 99.70 and 99.30% accuracy for cores and silos, respectively. The presented research is relevant to both researchers and practitioners. It provides practitioners with charts that assist in scheduling and managing the required resources for slip-form application. In addition, it provides researchers with simulation models and framework for implementing slip forms to core and silo construction. [ABSTRACT FROM AUTHOR]

Aeration filling is a new flask (or moulding chamber) filling method, which has been developed from the shooting/blowing process. As a sand filling stage, aeration filling determines the ultimate quality of mould in a sense, such as integrality and uniformity. If the moulding sand can be filled in every part of the mould cavity, an accurate shape would be replicated after the finial compaction stage, otherwise the mould may have weak regions. This paper focuses on the study of the sand filling process and its influential factors. From experiments and comparison with conventional shooting (or blowing) process, it can be seen that this method has the advantages of better sand filling effect and less energy consumption. [ABSTRACT FROM AUTHOR]

Recently, a press casting process using a greensand mould was actively developed by the authors' group to improve productivity and casting quality. This process consists mainly of two parts: in the first, molten metal is poured in the lower mould by a ladle, and in the second, the upper mould falls down toward the lower mould to press the molten metal. The feature based advantages of this greensand casting are an astonishing increase in casting yield (over 90%) and energy saving. A rapid pressing process should be realised as a vital task to achieve an increase in productivity. In addition, the advanced technique of this process will also suppress casting defects such as a cold shut and the inclusion of generated oxide film due to the temperature decrease in molten metal. As the technical problem on high speed pressing, the other defects are caused by increased pressure. Metal penetration, in which the solidified molten metal is soaked among the sand particles in greensand, often occurs. Hence, the authors propose controlling the pressing velocity in order to realise high production competence and to suppress the rapid increase in pressure. In this paper, a pressure suppression method in high speed pressing is proposed in which the sequential velocity control of the press can be applied to various casting moulds. The control design is conducted simply and theoretically, and a brief mathematical model of the fluid pressure is built using a complicated, exact model of CFD. Then, the permitted range of pressure fluctuation is given for the production of high quality casting. Considering the upper limit of the pressure constraint for defect free pressing, the switching velocity pattern of multisteps is derived using the proposed mathematical model without trial and error adjustment. The control performance for pressure fluctuation using the obtained velocity reference is checked by CFD simulations. [ABSTRACT FROM AUTHOR]

Deformation is one of the most common defects during the casting of large scale hydroturbine blades because of their curved three-dimentional (3D) surface geometry. Inverse deformation is usually applied to the pattern for sand moulds to finally obtain proper shape. However, the value of inverse deformation is hard to be determined. In this paper, a method is presented to determine the inverse deformation values by cycling numerical simulation. The inverse deformation is determined by the criteria of the achievement of even and appropriate machining allowance of the whole casting. This method is applied to a large scale blade casting used in the Three Gorges Power Plant. The calculated inverse deformation is obtained after three cycles. By using the electronic coordinate determination system (ECDS), its surface is measured and the machining allowance values of some points are acquired. The measured and calculated results are in agreement. [ABSTRACT FROM AUTHOR]

Abstract: The paper presents the geometrical non-linear response of unidirectional sandwich panels with a “soft” core subjected to thermally induced deformation type of loading, which may be fully distributed or localized. The mathematical formulation incorporates the effects of the flexibility of the core in the vertical direction as well as the effects of the temperature dependent mechanical properties of the constituent materials on the non-linear behavior. The non-linear governing equations are derived using a variational approach following the approach of the high-order sandwich panel theory (HSAPT). The features of the non-linear response are presented through a numerical study that discusses the effects of localized reinforced cores and the mismatch of the coefficients of thermal expansion of the constituent core materials; the effects of continuous panels in the presence of immovable supports; the effects of localized thermal loading with temperature dependent material properties and, finally, the interaction of mechanical and thermal loading on the response with and without immovable supports and temperature dependent material properties. An important conclusion of the study is that the interaction between mechanical loads, temperature induced deformations, and degradation of the mechanical properties due to elevated temperatures, may seriously affect the structural integrity. [Copyright &y& Elsevier]

Abstract: The possibility of severe recriticality could be excluded if the molten core materials are discharged from reactor core in the early stage of core disruptive accident (CDA). Based on this idea, several design measures for future commercial liquid metal-cooled fast breeder reactors (LMFBRs) have been proposed to enhance the molten fuel discharge from core in order to prevent formation of the core-wide molten pool with high mobility. One promising concept in these design candidates is modified-FAIDUS (Fuel subassembly with Inner DUct Structure). The event progression in unprotected loss of flow (ULOF) accident in a sodium-cooled large scale FBR with modified-FAIDUS was analyzed to assess the effectual performance of modified-FAIDUS in preventing severe recriticality using the SAS4A and SIMMER-III codes. Two parametric cases were performed covering the uncertainty of duct wall failure mechanism, one with stable fuel crust and another with unstable crust condition. The calculation showed that the final amount of discharged fuel from core in both cases was more than 20% of initial core inventory. The degraded core after fuel discharge is composed of the mixture of solidified fuel, swollen fuel chunks and molten steel, of which low mobility prevents massive fuel motion. The reactor power lowered to decay heat level and the reactivity lowered around −20$, thus, the possibility of severe recriticality was eliminated. [Copyright &y& Elsevier]

Abstract: This work deals with the analysis of the mechanical behaviour of a class of sandwich structures widely employed in marine constructions, constituted by fiber-glass laminate skins over PVC foam or polyester mat cores. In detail, a systematic experimental study and numerical simulations have shown that the theoretical prediction of the strength and the actual failure mechanism of these sandwich structures can be affected by significant errors, specially in the presence of prevalent shear loading. Moreover, because of the low shear stiffness and the elastic constants mismatch of the skins and core material, failure modes and strength are strongly influenced by eventual stresses orthogonal to the middle plane of the sandwich. In particular, for the sandwich structures with a PVC foam core, such a stress interaction leads to early skin–core delamination failure, whereas for those with a polyester core it leads to core shear-cohesive failure. By means of accurate non-linear simulations, accurate failure criteria, that can be used at the design stage in the presence of complex loading, have also been developed. [Copyright &y& Elsevier]

Abstract: The paper addresses the damage tolerance of sandwich structures, where the prevention and limitation of delamination failure are highly important design issues. Due to the layered composition of sandwich structures, face–core interface delamination is a commonly observed failure mode, often referred to as peeling failure. Peeling between the sandwich face sheets and the core material drastically diminishes the structural integrity of the structure. This paper presents a new peel stopper concept for sandwich structures. Its purpose is to effectively stop the development of debonding/delamination by rerouting the delamination, and to confine it to a predefined zone in the sandwich structure. The suggested design was experimentally tested for different material compositions of sandwich beams subjected to three-point bending loading. For all the tested sandwich configurations the suggested peel stopper was able to stop face–core delamination and to limit the delamination damage to restricted zones. [Copyright &y& Elsevier]

We demonstrate in this work that 2-μm-sized Ag (μAg) powders can be used as a core material for constructing biomolecular sensing/recognition units operating via surface-enhanced resonance Raman scattering (SERRS). This is possible because μAg powders are very efficient substrates for both the diffuse reflectance IR and the surface-enhanced Raman scattering–SERRS spectroscopic characterization of molecular adsorbates prepared in a similar manner on silver surfaces. Besides, the agglomeration of μAg particles in a buffer solution can be prevented by the layer-by-layer deposition of cationic and anionic polyelectrolytes such as poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA). In this particular study, we used rhodamine B isothiocyanate (RhBITC) as a SERRS marker molecule, and μAg powders adsorbed consecutively with RhBITC and PAH–PAA bilayers were finally derivatized with biotinylated poly( l-lysine). On the basis of the nature of the SERRS peaks of RhBITC, those μAg powders were confirmed to selectively recognize streptavidin molecules down to concentrations of 10−10 g mL−1. Since a number of different molecules can be used as SERS–SERRS marker molecules, the present method proves to be an invaluable tool for multiplex biomolecular sensing/recognition via SERS and SERRS. [ABSTRACT FROM AUTHOR]

Abstract: Using the central composite design, we have designed the experimental platform for optimizing γ-oryzanol (GO) microencapsulation. Response surface methodology (RSM) was applied to explore maximal microencapsulation yield (MY) using three independent variables; the ratio of core materials to coating materials (X 1), temperature of dispersion fluid (X 2), and emulsifier concentration (X 3). As a result of least-square regression (RSREG) analysis, the regression model equation for the MY (%) to the change of independent variables could be predicted as follows; . Applying this model equation to the surface plot and canonical analysis, the optimal conditions for the GO microencapsulation were determined to be 4.8:5.2 (X 1), 24.99 (X 2) and 0.38% (X 3). The resulting MY, with statistically optimized parameters, was 95.7%. The thiobarbituric acid-reactive substances (TBARs) values of heated lard were determined to evaluate the effect of microencapsulation on the stability against heat-induced lipid oxidation. The MGO (microencapsulated γ-oryzanol)-treated lard displayed significantly greater oxidative stability than did the GO-treated lard up to a 10-day heating period. During the heating process, a substantially larger amount of GO remained in the MGO-treated lard as well. Apparently, microencapsulation could be used as a good potential technique to protect GO from the heat-induced loss of its antioxidant effect. [Copyright &y& Elsevier]

Abstract: We have generalized the pressure–volume (P–V) relationships using simple polynomial and logarithmic expansions so as to make them consistent with the infinite pressure extrapolation according to the model of Stacey. The formulations are used to evaluate P–V relationships and pressure derivatives of bulk modulus upto third order (K′, K″ and K‴) for the earth core material taking input parameters based on the seismological data. The results based on the equations of state (EOS) generalized in the present study are found to yield good agreement with the Stacey EOS. The generalized logarithmic EOS due to Poirier and Tarantola deviates substantially from the seismic values for P, K and K′. The generalized Rydberg EOS gives almost identical results with the Birch—Murnaghan third-order EOS. Both of them yield deviations from the seismic data, which are in opposite direction as compared to those found from the generalized Poirier–Tarantola logarithmic EOS. [Copyright &y& Elsevier]

Abstract: Fatigue failure of a gas-nitrided 4140 steel under axial cyclic loading results from a competition between surface crack initiation in the nitrided case and internal “fish-eye” cracking inside the core material. When nitriding is deep enough, the internal mechanism prevails in smooth specimens and fatigue strength improvement as compared to base metal is about 20% at 106 cycles. In the present study, three V-notched specimens (blunt, medium, and severe) are designed to be representative of the stress gradient: (i) in a small rotary bending specimen, (ii) at the root of a gear tooth, and (iii) at the root of a very sharp notch. The cracking mechanism depends on the notch severity. The nitrided blunt notch fails from a fish-eye nucleated at the case/core boundary, whereas the medium and sharp notches fail from surface cracks. The high-cycle fatigue strength improvement varies from 80% for the blunt notch and to more than 100% for the sharp notch. The notch fatigue behaviour of nitrided steel is discussed by comparing the evolutions of internal and surface fatigue strengths with relative stress gradient. [Copyright &y& Elsevier]

Polymeric aerogels are used in this study to bind foundry sand forming thus a new kind of mould and core material called AeroSand. A core and mould material in general shall be able to withstand all handling stresses in a foundry shop, withstand the thermal and mechanical stresses exerted onto them during casting, but should also easy removable from a casting. Therefore mechanical properties are important besides others and this paper therefore concentrates on bending and compression strength of AeroSands. It is shown that the strength levels obtainable with aerogel binders are comparable to conventional binder systems. One essential advantage of AeroSands, namely the easy core removal, is not payed off by a loss in strength. The mechanical properties can be explained using a simple extension of the Griffith criterion taking into account the microstructure of the sand aerogel composite and the fracture path. [ABSTRACT FROM AUTHOR]

The objectives of this study are to investigate the basic mechanical properties of TEEK-L polyimide-foam of a balloon type and TEEK-L filled aramid-honeycomb core-materials for sandwich structures and to compare their mechanical properties with those of AIREX R82 and ROHACELL WF foam core-materials. Compression, tension, and plate-shear tests provided their stress–strain relationships, elastic modulus, and strength. The test results are compared and discussed. The major results obtained are: (1) Filling the aramid honeycomb cells with TEEK-L can improve the basic mechanical properties of an aramid-honeycomb core-material, in particular making them higher than the values expected from the principle of superposition for compression tests and equal to the values expected from superposition for plate-shear tests. (2) The basic mechanical properties of the TEEK-L filled aramid honeycomb are superior to those of AIREX R82 110 and equivalent to those of ROHACELL WF 110, where the three materials have equal densities. (3) The basic mechanical properties of TEEK-L are inferior to those of AIREX R82 60 and ROHACELL WF 51, when materials with equivalent densities are compared. (4) TEEK-L filled aramid honeycomb has high potential as a new core material for aerospace sandwich structures. [ABSTRACT FROM AUTHOR]

Abstract: The paper addresses the problem of sandwich beams/panels with junctions between different core materials. The physics of the impairing local effects induced by a mismatch of the elastic material properties at core junctions is discussed, and the results of an experimental investigation concerning the quasi-static failure behavior of sandwich beams with conventional butt and “structurally graded” core junctions is discussed. The term “structurally graded” core junctions include scarf junctions and junctions provided with local reinforcing patches of the faces. The influence of the junction interface geometry on the quasi-static deformation, failure initiation and crack patterns are studied experimentally for sandwich beams loaded in the three-point bending. It is shown that “structurally graded” core junctions perform better than conventional butt junctions, and thus improve the strength of the structure. [Copyright &y& Elsevier]

Abstract: Sandwich beams with inclusion of different core materials were the subject of the experimental study [Bozhevolnaya E, Thomsen OT. Structurally graded core junctions in sandwich beams: quasi-static analysis. Compos Struct, in press], which focused on the static performance of such sandwich elements. The concept of structurally graded core junctions, suggested in [Bozhevolnaya E, Thomsen OT. Structurally graded core junctions in sandwich beams: quasi-static analysis. Compos Struct, in press], presents different geometrical shapes of the core interfaces (e.g. bias junctions) as well as core junctions with locally reinforced faces. The novel design of core junctions was shown to provide larger critical static loads and more beneficial crack initiation and propagation patterns in sandwich beams. This paper is devoted to a comparative study of the performance of sandwich beams with conventional and structurally graded core junctions under fatigue loading conditions. An experimental investigation of the fatigue behaviour of the sandwich beams was performed using a three-point bending loading scheme. A rigorous statistical treatment of the experimental data has shown that structurally graded core junctions perform much better than conventional butt junctions. Thus, the fatigue life of the sandwich beams with structurally graded core junctions was up to 30% higher than the fatigue life of the sandwich beams with the conventional junction design. [Copyright &y& Elsevier]

Core inserts in sandwich panels substitute parts of the original core material in a sandwich element, and the main purpose of the core inserts is to supply a local reinforcement of the sandwich panel for a subsequent introduction of the external loads. The new design of the core insert substantially diminishes the level of impairing local effects in the faces. The suggested insert is structurally graded by means of shaping insert boundaries to be inclined with respect to the sandwich faces, which provides smoothing of material discontinuities at the junction of different materials. The new design of the core insert is studied experimentally, and the design parameters of the core insert are studied with the help of the finite element modelling (FEM). [Copyright &y& Elsevier]

Conventional analysis methods for beams do not distinguish between transverse loads that are applied at the beam centroidal axis and those acting either above or below the centroidal axis. In contrast, this paper formulates a sandwich beam finite element solution which models the effect of load height relative to the centroidal axis. Towards this goal, the governing equilibrium equations and associated boundary conditions are derived based on a Timoshenko beam formulation for the core material. Special shape functions satisfying the homogeneous form of the equilibrium equations are derived and subsequently used to formulate exact stiffness matrices. By omitting the stiffness terms related to the faces, the formulation for a homogeneous Timoshenko beam can be recovered. Also, the Euler–Bernouilli counterpart of the formulation is recovered as a limiting case of the current Timoshenko beam formulation. Effects of load height relative to the centroid are observed to have similarities with those induced by axial forces in beam-columns. For a simply supported beam, downward acting loads located below the centroidal axis are found to induce a stiffening effect while those acting above the centroidal axis are found to induce a softening effect, resulting in higher transverse displacements. [ABSTRACT FROM AUTHOR]

Abstract: This paper deals with the design of thin, all-metal sandwich sheets for forming applications. Draw bending experiments have been performed on thin prototype sandwich materials with metallic cores of 10% relative density. The experimental results reveal core shear failure as the dominant failure mechanism. Detailed finite element analysis has been carried out to gain further insight in the mechanics of bending and unbending of sandwich sheets. Based on theoretical analysis, design maps have been constructed describing the required core shear strength as a function of the face sheet properties as well as the sandwich core thickness and the draw radius. Furthermore, the relationship between shear strength and relative density has been determined for perforated sandwich core materials. The main result of this study is that the shear strength of formable sandwich sheets should be at least one order of magnitude higher than that of most commercial cellular solids. Here, perforated sandwich cores of relative densities above 25% are suggested to prevent sandwich sheets from core shear failure in forming operations. [Copyright &y& Elsevier]

Hollow particles, called microballoons, are commonly used in the fabrication of syntactic foams, which are used as core materials in sandwich composites. The present experimental investigation aims at characterizing five different types of syntactic foam core sandwich composites for their edgewise compressive strength. The microballoon volume fraction is maintained at 0.65 in each type of syntactic foams. The five types of microballoons used in the study have the same mean outer diameter of about 40 μm but different wall thickness causing a difference in their densities and strengths. The differences in the compressive strength and modulus of sandwich composites are related to the microballoon radius ratio, which is defined as the ratio of the internal to the external radii of the microballons. It is observed that the compressive strength and modulus of syntactic foams increase with a decrease in the microballoon radius ratio. The specimen fracture features are also discussed. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a simple analytical model for the prediction of thermo-elastic deformation (spring-in) of angled composite sandwich panels. The development of the model is presented and the simplifying assumptions are clearly defined. Contributions from different mechanisms are clearly shown which gives a good understanding of the problem. The analytical model is validated against a finite element model and the validity of the simplifying assumptions is examined. The agreement between predicted spring-in from the analytical model and the finite element model is very good for the studied sandwich panels with composite skins and varying core materials. The difference in spring-in predictions is less than 0.05° for all cases studied. The simplicity of the model together with the limited number of input parameters makes it a practical tool for composite manufacturing engineers and designers. [Copyright &y& Elsevier]

Phospholipid particles for pharmaceutical applications were prepared by spray-drying processing and characterized for their structural, thermodynamic and physical properties. The lipid particles were spherical and potentially suitable for pulmonary applications (aerodynamic diameter less than 5 μm), for tablet preparations of orally administered drugs or as proliposomes in liquid formulations. The operational conditions, such as nozzle diameter, lipid concentration, flow rate and temperature of the feed solution, as well as the concentration of mannitol, the core material, were found to affect the particle properties, thus allowing them to be modified through the processing conditions. When mannitol was incorporated into formulations containing 20 or 45 mM lipid, at a feed flow rate of 3 ml/min, the resulting structures were more amorphous. More crystalline structures were obtained when the feed solution temperature and the nozzle diameter were increased from 25 to 60 °C and from 0.5 to 1 mm, respectively. The physical and chemical stability of the particles was preserved when they were stored under refrigeration, as shown by the water activity measurements and differential scanning calorimetry (DSC). These results show the potential of spray-dried particles for drug delivery applications. [Copyright &y& Elsevier]

We review come of the latest developments in core materials and sandwich composite structures. Amanda Jacob reports. [Copyright &y& Elsevier]

In high-density interconnection technologies the size of via holes significantly effects the space available for component assembly. Commonly used CO2 lasers do not produce microvias small enough for future demands. In this paper we investigate metallization of UV-laser drilled microvias by magnetron sputtering.The core material of the test boards was a copper-clad FR-4 laminate. The boards were coated with two types of nonphotoimageable liquid dielectrics. A thin chrome layer (∼0.1 μm) with a subsequent copper layer (∼3 μm) or copper layer without any intermediate chrome layer was sputtered onto the surfaces and within the microvias. Copper was electrolytically grown onto the sputtered metal layers. In fine lines the adhesion of the metallic layer to the core material is essential. Our earlier studies have shown that chrome has good adhesion to epoxy and it is used as a seeding layer between epoxy and sputtered copper.The purpose of our research is to assess the usefulness of sputtering techniques for metallizing small vias and to find a combination of dielectric material, technologies for microvia formation and plating for achieving reliable microvia connections. Microvias were analyzed after every process stage by means of a microscope and a scanning electronic microscope. [Copyright &y& Elsevier]

The quality of wavelength shifting fibres depends on two basic parameters: the transparency of the core material, polystyrene, and the reflection coefficients at the fibre internal interfaces (core–clad and clad–clad in double-clad fibres). We have developed a model to parameterize these effects. The model has been applied to study the light attenuation in fibres used in the ATLAS hadronic calorimeter (TILE Calorimeter), as well as in the ones produced by several firms. [Copyright &y& Elsevier]

End grain balsa is a common core material in sandwich structures. The main properties of interest of a sandwich core, in particular for marine applications, are the shear stiffness and shear strength. The end grain arrangement does not fully utilize the anisotropy of balsa wood for the benefit of shear properties. A new arrangement of balsa blocks in a sandwich core was developed and numerically analyzed. This new core, which consisted of an assembly of oddly shaped balsa blocks, allowed the grains in various balsa blocks to be oriented for example at 45° to the normal of the core. The effective out-of-plane shear stiffness was isotropic. Numerical analyses predicted a superior shear stiffness, which was confirmed by preliminary tests. [Copyright &y& Elsevier]

Application of fine-grained doubly oriented electrical steel sheets that have a strong {100}(001) texture to synchronous interior permanent magnet motors has been investigated. The alteration in stator core material from high grade nonoriented electrical steel sheets to the doubly oriented material with a simple change in stator design was found to lead to an increase in efficiency up to more than 2%. This efficiency increase is ascribed to a larger permeability and a lower iron loss in two perpendicular directions of the doubly oriented material. Finite-element analysis has revealed that the magnetic field distribution in stator cores made of the doubly oriented material is largely different from that in stator cores made of the nonoriented material. [ABSTRACT FROM AUTHOR]

This paper presents the results of two-dimensional (2-D) finite-element analysis (FEA) carried out on 8/6 and 6/4 doubly salient permanent magnet (DSPM) motors to arrive at the magnet leakage factor and the flux density ratios of various parts of the motors so as to aid the designers of this newer motor. The two permanent magnets being kept embedded in the stator halves along with the typical doubly salient structure of the DSPM motor causes more leakage of the magnet flux. After extensive FEAs of the two configurations of the motors, it is observed that a magnet leakage factor of 132 is giving the correct results for use in conventional designs of this motor. Based on the optimum designs of the two motors, the flux densities in the airgap, rotor yoke, rotor pole, and stator yoke can be 1, 0.5, 0.9, and 0.5 times the flux density considered for the stator pole, which will normally be just above the knee-point value of the B-H characteristics of the core material used. [ABSTRACT FROM AUTHOR]

The article highlights the papers that are presented at the 8th International Conference on Sandwich Structures (ICSS-8) in Porto, Portugal. They include "Evaluation of new crack suppression method for foam core sandwich panel via fracture toughness tests and analyses under mode-I type loading," "Development of a mechanical technology for joining sandwich elements," and "Mechanical behaviour of sandwich structures using natural cork agglomerates as core materials.

This article focuses on the study entitled The Resistance of Clamped Sandwich Beams to shock loading, conducted by N. A. Fleck and V. S. Deshpande. Fleck and Deshpande propsed an analytical model to encapsulate the response of clamped sandwich beams to blast loadings in air and under water. Issues which require clarification include 1) the application of Taylor's model to air blast loadings, 2) the limiting impulse transferable to a stationary rigid face in an air blast 3) inconsistencies in the proposed shock model and 4) application of the shock theory to certain micro-architecture core materials.

COLOMBIAN core material manufacturer Aurora de Columbia is increasing production of and developing its nonwoven and balsa wood core materials.This is a short news story only. Visit www.reinforcedplastics.com for the latest plastics industry news. [Copyright &y& Elsevier]