Multilayer Core Research Articles

Hierarchical hollow MnO/carbon fiber@WS2 composite material exhibits strong wideband electromagnetic wave attenuation

Constructing multi-layer heterogeneous interfaces has been studied as one of the important means to optimize electromagnetic wave absorption performance. WS2, as a special layered material with high specific surface area and multiple anionic vacancies, although its multi-layered interface structure cannot meet the requirements of all absorbing materials, composite absorbers designed through composition and structure are undoubtedly not one of the strategies to improve absorption bandwidth. In this study, we utilized the defect rich characteristics of WS2 Nano flowers and designed a multi-layer core–shell MnO/CF@WS2 (H-MCW) hybrid materials using carbon fiber (CF) as a carrier to provide a carbon source. The core cavity of H-MCW is conducive to multiple scattering of electromagnetic waves, with a large number of defects leading to an increase in electrochemical active sites in the material, and enhanced dipoles helping to improve impedance matching. This work provides a new method for designing lightweight thin film absorbing materials.

Magnolol-loaded polydopamine-chitosan coated pH-responsive nanoparticles for alleviation of ulcerative colitis

This study designed and developed a novel three-layer electrostatic, slow-releasing nanoparticle drug delivery system for the treatment of ulcerative colitis. The nanoparticles were composed of layers of zein-based polydopamine, chitosan and cellulose acetate phthalate to form a polyelectrolyte multilayer core−shell nanoparticle structure. The anti-inflammatory natural product magnolol was chosen to be the model drug for the study. The nanoparticles (260.50 ± 23.90 nm) were prepared with layer-by-layer coating and then assessed in vitro and in vivo using a mouse model of ulcerative colitis. The in vitro data confirmed the slow-releasing and pH-dependent characteristics of particles. Quantitative analysis of the in vivo distribution of Mag in mice showed significantly higher concentrations in colonic tissue than in the upper gastrointestinal tract (854.6 ng/g vs 291.5–351.1 ng/g, respectively). Histological and pro-inflammatory cytokine analysis indicated that the nanoparticles had a significant anti-inflammatory effect and were protective against DSS-induced structural damage of the colonic mucosal structure. These results confirm that this nano-delivery system could increase the levels of Mag reaching the colon, resulting in greater efficacy than free Mag in treating UC in this mouse model.

Low-cycle fatigue behavior and microstructure evolution of ODS steel pipes at high temperatures

Oxide-dispersion-strengthened (ODS) steels are candidate materials for application in advanced nuclear reactors. In this study, the low-cycle fatigue performances of 13Cr-ODS ferritic steel pipes were investigated at 600, 700, and 800 °C. Cyclic softening was observed at high strain amplitudes with an increase in the number of fatigue cycles. However, cyclic hardening appeared first, and then cyclic softening occurred at a low strain amplitude with the increase in the number of fatigue cycles. By comparing the cyclic stress–strain curves and the monotonic stress–strain curves, it was found that cyclic softening occurred regardless of the strain amplitude. The Coffin–Manson and Basquin equations were used to predict the fatigue of the pipes. Microstructure analysis indicated that cyclic softening was induced by the dynamic recovery and recrystallization, which reduced the number of low-angle grain boundaries in the deformed grains by promoting dislocation annihilation and reorganization. A complex multi-layer core–shell structure with a large size (∼500 nm) was observed.

Nonlinear poro-thermo-forced vibration in curved sandwich magneto-electro-elastic shells under hygrothermal environment

This research employs a multiple scales perturbation approach to evaluate the nonlinear wave propagation behaviors of a doubly curved sandwich composite piezoelectric shell with a flexible core in a hygrothermal environment. Stress and strain calculations for the flexible core and face sheets are carried out using Reddy's third-order shear deformation theory (TSDT) and third-order polynomial theory, respectively. The study explores the synergistic effects of a multilayered shell, flexible core, and magneto-rheological layer (MR) in revealing the nonlinearity of both in-plane and vertical moment within the core. The Halpin–Tsai model is employed to derive the properties of polymer/carbon nanotube/fiber (PCF) and polymer/graphene platelet/fiber (PGF) three-phase composite shells. The governing equations for the multiscale shell are derived using Hamilton's formulation. The research investigates temperature variations, diverse distribution patterns, curvature ratios, and magnetic fields through numerical analysis, presenting the results graphically and prior research has demonstrated the accuracy of these methods. Notably, these factors exert significant influence on the frequency-amplitude curves of the smart structure.

Ytterbium-Doped Double-Clad Fiber with High Uniformity of Concentration Distribution and Suppressed Photodarkening

Photodarkening (PD) effect in ytterbium-doped fiber (YDF) has a significant impact on the high-power operational stability of fiber lasers, which seriously hinders the power scaling. In this paper, the relationship between ytterbium ions uniformity and the photodarkening effect in the YDF was investigated, and the fabrication process allowing improving the ytterbium ions uniformity in the core of preforms for suppressing the photodarkening effect was developed. The Modified Chemical Vapor Deposition (MCVD) method combined with Chelate Vapor Deposition (CVD) technology was adopted for multi-layer fiber core deposition, and an all-gas-phase technical process was proposed to improve the ytterbium ions uniformity in the Al/P co-doped glass matrix. The 25/400 μm YDFs obtained by this technology achieved stable 3.5 kW laser output power for 8 h with suppressed PD and nonlinear effects.

African swine fever: analysing its epidemiology, pathogenesis and control strategies: a review

African Swine Fever Virus (ASFV) poses a significant threat to global swine populations, with devastating economic and agricultural implications. This review article provides a comprehensive examination of various facets of ASFV, encompassing its structure, entry mechanism, transmission dynamics, clinical signs, pathogenesis, diagnosis and control strategies. The complex virion architecture, including the multilayered core and distinctive outer envelope, is explored, shedding light on key elements influencing the virus’s stability and infectivity. The intricate mechanisms governing ASFV entry into host cells are discussed, emphasizing the interplay between viral proteins and cellular receptors. Insight into the virus-host interaction provides a foundation for understanding the initial stages of infection, influencing subsequent pathogenesis. Transmission dynamics, a critical aspect of ASFV epidemiology, are examined, encompassing both direct and indirect modes of spread. Factors influencing the persistence of ASFV in diverse environments and the role of vectors in disease dissemination are explored to elucidate the complex transmission pathways. Clinical signs and pathogenesis of ASFV infection are thoroughly reviewed, outlining the diverse manifestations in swine species. The immunopathological responses and host factors influencing disease severity are discussed, enhancing our understanding of ASFV pathobiology. A comprehensive understanding of diagnostic tools is pivotal for timely and accurate disease detection, enabling swift intervention measures. In conclusion, this review provides a nuanced and integrative overview of ASFV, offering valuable insights for researchers, veterinarians and policymakers engaged in combatting this significant threat to the swine industry.

Effects of internal configurations and its processing quality on compressive performance for 3D printed continuous fiber reinforced composites honeycomb sandwich

Continuous fiber reinforced composites (CFRCs) 3D printing technology has the advantage of integrated fabricating for honeycomb sandwich structures, the load-bearing capacity of the fabricated honeycomb sandwich structures still needs to be investigated and improved. This study aims to reveal compression failure modes of 3D printed CFRCs honeycomb sandwich structures with various internal configurations by conducting flatwise compression tests. The deviations of single-layer CFRCs honeycomb cores with different core sizes and core heights and their impacts on the compression failure process were analyzed. A 3D printing method with multilayer cores and core/panel variable printing thickness was proposed, and the effects of multilayer core structure and different core printing parameters on the compressive properties of honeycomb sandwich structures were investigated. The results showed that interlayer cracking caused by core buckling deformation was the leading cause of failure of 3D printed CFRCs honeycomb sandwich structures when subjected to compression. The core buckling deformation could be suppressed by printing multilayer cores and using low core printing thickness, and the compression strength and specific energy absorption of the sandwich structures reached 38.1 MPa and 25.4 kJ/kg, respectively. This study provides guidance for the customization of the 3D printing process of CFRCs honeycomb sandwich structures.

Primary Cardiac Intimal Sarcoma: Multi-Layered Strategy and Core Role of MDM2 Amplification/Co-Amplification and MDM2 Immunostaining.

Primary cardiac tumours are relatively uncommon (75% are benign). Across the other 25%, representing malignant neoplasia, sarcomas account for 75-95%, and primary cardiac intimal sarcoma (PCIS) is one of the rarest findings. We aimed to present a comprehensive review and practical considerations from a multidisciplinary perspective with regard to the most recent published data in the specific domain of PCIS. We covered the issues of awareness amid daily practice clinical presentation to ultra-qualified management in order to achieve an adequate diagnosis and prompt intervention, also emphasizing the core role of MDM2 immunostaining and MDM2 genetic analysis. An additional base for practical points was provided by a novel on-point clinical vignette with MDM2-positive status. According to our methods (PubMed database search of full-length, English publications from January 2021 to March 2023), we identified three studies and 23 single case reports represented by 22 adults (male-to-female ratio of 1.2; male population with an average age of 53.75 years, range: 35-81; woman mean age of 55.5 years, range: 34-70) and a 4-year-old child. The tumour-related clinical picture was recognized in a matter of one day to ten months on first admission. These non-specific data (with a very low index of suspicion) included heart failure at least NYHA class II, mitral regurgitation and pulmonary hypertension, acute myocardial infarction, ischemic stroke, obstructive shock, and paroxysmal atrial fibrillation. Awareness might come from other complaints such as (most common) dyspnoea, palpitation, chest pressure, cough, asthenia, sudden fatigue, weakness, malaise, anorexia, weight loss, headache, hyperhidrosis, night sweats, and epigastric pain. Two individuals were initially misdiagnosed as having endocarditis. A history of prior treated non-cardiac malignancy was registered in 3/23 subjects. Distant metastasis as the first step of detection (n = 2/23; specifically, brain and intestinal) or during follow-up (n = 6/23; namely, intestinal, brain and bone, in two cases for each, and adrenal) required additional imagery tools (26% of the patients had distant metastasis). Transoesophageal echocardiography, computed tomography (CT), magnetic resonance imagery, and even 18F-FDG positronic emission tomography-CT (which shows hypermetabolic lesions in PCIS) represent the basis of multimodal tools of investigation. Tumour size varied from 3 cm to ≥9 cm (average largest diameter of 5.5 cm). The most frequent sites were the left atrium followed by the right ventricle and the right atrium. Post-operatory histological confirmation was provided in 20/23 cases and, upon tumour biopsy, in 3/23 of them. The post-surgery maximum free-disease interval was 8 years, the fatal outcome was at the earliest two weeks since initial admission. MDM2 analysis was provided in 7/23 subjects in terms of MDM2-positive status (two out of three subjects) at immunohistochemistry and MDM2 amplification (four out of five subjects) at genetic analysis. Additionally, another three studies addressed PCISs, and two of them offered specific MDM2/MDM2 assays (n = 35 patients with PCISs); among the provided data, we mention that one cohort (n = 20) identified a rate of 55% with regard to MDM2 amplification in intimal sarcomas, and this correlated with a myxoid pattern; another cohort (n = 15) showed that MDM2-positive had a better prognostic than MDM2-negative immunostaining. To summarize, MDM2 amplification and co-amplification, for example, with MDM4, CDK4, HMGA3, CCND3, PDGFRA, TERT, KIT, CCND3, and HDAC9, might improve the diagnosis of PCIS in addition to MDM2 immunostaining since 10-20% of these tumours are MDM2-negative. Further studies are necessary to highlight MDM2 applicability as a prognostic factor and as an element to be taken into account amid multi-layered management in an otherwise very aggressive malignancy.

Large‐Area Knittable, Wash‐Durable, and Healable Smart Fibers for Dual‐Modal Sensing Applications

AbstractFiber‐based multimodal sensors with electrical/optical signals are highly desired for next‐generation wearable electronics. Despite the remarkable progress in this area, achieving large‐scale knittable, washable, and self‐healing performance in fiber‐based multimodal sensors simultaneously remains a great challenge. Here, a smart fiber capable of exhibiting piezoresistive/luminescent properties based on an H‐bonding connected multilayered core–shell nanostructure is developed. The core principle of this design involves constructing strong interfacial interactions between the fiber layers, which results in a sensor with high sensitivity (gauge factor = 12383500), exceptional water resistance, and robust self‐healing properties (tensile strength 30.9 MPa, healing efficiency 72.9%). Unlike traditional fiber‐based sensors where elaborate nanostructures are prone to shedding during knitting, this strategy enables the fiber sensors with excellent knittability to be patterned in the fabric, improving both optical and electrical sensitivities. This work is anticipated to make a significant contribution to the further development of wearable electronic products and visual human–computer interaction electronic devices.

Compressive Strength and Elastic Modulus of a 3D Woven Glass/Polyester Fire-Retardant Sandwich Composite

A 3D woven sandwich composite structure has been widely used in various fields due to its advantages in terms of its strength-to-weight ratio. The adoption of lightweight materials in the railway industry for train carriages is aligned with United Nations Sustainable Development Goal 11, as this fosters the development of sustainable transportation by reducing carriage weight, enhancing fuel efficiency, minimizing component wear, and mitigating air pollution. This study explores the effect of the addition of aluminum trioxide (ATH) filler on the core structure, density, compressive strength, elastic modulus, and the number of added layers of 3D woven core fabric with 2D woven face sheets. Sandwich composites were produced with varying ATH loads of 30%, 40%, and 50%. We also varied the number of 3D woven core fabric layers in the composite sandwich (one, two, three, and four layers) and the 2D preform (one on the upper side, two on the upper side, and one on the upper + two on the lower sides) used as a face sheet thickener. The results showed that the addition of ATH filler increased the composite density. The addition of up to 40% ATH improved the strength and elastic modulus of the composite, while excessive loading led to a decrease in both properties. Variation of the 3D and 2D preform layers also improved the compressive strength and elastic modulus. We conclude that 3D woven sandwich composites incorporating 40% ATH, multilayered 3D woven core fabric, and 2D woven fabric face sheet thickener represent promising materials for use in the railway industry.

Structures of AT8 and PHF1 phosphomimetic tau: Insights into the posttranslational modification code of tau aggregation

The microtubule-associated protein tau aggregates into amyloid fibrils in Alzheimer's disease and other neurodegenerative diseases. In these tauopathies, tau is hyperphosphorylated, suggesting that this posttranslational modification (PTM) may induce tau aggregation. Tau is also phosphorylated in normal developing brains. To investigate how tau phosphorylation induces amyloid fibrils, here we report the atomic structures of two phosphomimetic full-length tau fibrils assembled without anionic cofactors. We mutated key Ser and Thr residues to Glu in two regions of the protein. One construct contains three Glu mutations at the epitope of the anti-phospho-tau antibody AT8 (AT8-3E tau), whereas the other construct contains four Glu mutations at the epitope of the antibody PHF1 (PHF1-4E tau). Solid-state NMR data show that both phosphomimetic tau mutants form homogeneous fibrils with a single set of chemical shifts. The AT8-3E tau rigid core extends from the R3 repeat to the C terminus, whereas the PHF1-4E tau rigid core spans R2, R3, and R4 repeats. Cryoelectron microscopy data show that AT8-3E tau forms a triangular multi-layered core, whereas PHF1-4E tau forms a triple-stranded core. Interestingly, a construct combining all seven Glu mutations exhibits the same conformation as PHF1-4E tau. Scalar-coupled NMR data additionally reveal the dynamics and shape of the fuzzy coat surrounding the rigid cores. These results demonstrate that specific PTMs induce structurally specific tau aggregates, and the phosphorylation code of tau contains redundancy.

Thermal characteristics of multilayer sandwich Nomex honeycomb core composite with heating elements for railways wall panels

The composite material has been widely used in vehicle interiors, particularly in applications such as the wall-side panels of railways. The sandwich honeycomb composite, which combines two composite skins with a metal honeycomb, is the preferred structure in aerospace and railway applications due to its rigidity at minimal weight. As a functional composite material that provides heat flux to passengers, a multilayer sandwich Nomex honeycomb core composite with heating elements has been developed. In this design, the heating element is inserted into the inner composite material as a heat generation component, producing heat transferred to the other side of the panel. The thermal and structural behaviors of the sandwich composite with heating elements are orthotropic and require careful assessment to understand the material characteristics of the developed composite parts. In this study, conduction heat transfer in the functional honeycomb composite is simulated using the Finite Element Method (FEM) and validated with experimental results. The study proposes three steps to solve the problem: determining the heat-transfer parameters, simplifying the Nomex honeycomb core, and conducting a full-scale heat-transfer simulation. This research aids operating systems in controlling the heat generator input to prevent dangerous conditions. The results indicate that the simulation trends closely align with the experimental results.

TRU utilization and MA transmutation in thorium-based fluorinated molten salt fast reactor

In this paper, a thorium-based fluorinated molten salt fast neutron reactor is taken as the research object, and the utilization of thorium resources, reuse of transuranic waste (TRU), and transmutation of minor actinide (MA) in fast reactor are the research purpose. The fast reactor adopts a multi-layer core structure, in which the fuel is divided into an inner fission fuel zone and an outer breeding fuel layer, respectively loaded with fluorinated molten salts LiF+ThF4+XF4 (where X is 233U, TRU, or 233U+MA) and LiF+ThF4. In addition to serving as nuclear fuel, these two molten salts also act as coolants in the primary circuits.Through the cross sections of nuclear reactions, transmutation chain of actinide nuclides, and the particle population density formula of actinide nuclides in nuclear reaction equilibrium, the possible nuclear reactions of actinide nuclides in thorium-based fast reactors are analyzed. The calculated results show that the thorium-based fast reactor has the following characteristics: fast neutron energy spectrum, negative temperature reactivity coefficient, effective utilization of thorium resources, the ability to breed fissle fuel such as 233U, production of high-purity radioisotope 238Pu material, and the ability to incinerate Pu and MAs in the TRU spent fuel.In the 233U fuel scheme, the 233U fuel is breeded, breeding ratio of fissile fuels is 1.21, the reaction products contain very little Np, and almost no Pu, Am, and Cm long-lived radionuclides. In the TRU fuel scheme, the annual capacity to incinerate MAs and Pu is 1072.6 kg, while producing a large amount of 233U and 233Pa fuel (together 1162.5 kg/year).In the 233U+2.0 wt% TRU-MAs fuel scheme, 127.35 kg of MA waste can be incinerated annually, and their transmutation rate is 15.95%, which is equivalent to the annual production of MA nuclear waste from 4.9 conventional 1000 MWe light water reactors. Here, TRU-MAs is the mixtured MA fuels after separation of Pu from the TRU fuel. At the same time, radioactive fuel 238Pu, which can be used for space nuclear power, is produced with an annual yield of 87.89 kg and an isotopic abundance of 87.57%. If the added TRU-MAs fuel is replaced with 2.0 wt% 237Np fluorinated salt, the annual yield and isotope abundance of 238Pu are further increased to 130.24 kg and 95.4%.

Heterostructure CoFe@(Co0.5Fe0.5)S@NCNT anchored on rice husk-based hierarchical porous carbon as a bifunctional cathode catalyst for Zn–air batteries

A bifunctional catalyst, characterized by its sea urchin-like morphology and multi-layer core–shell structure (CoFe@(Co0.5Fe0.5)S@NCNT), was synthesized within the restriction of RHPC' hierarchical pore structure.

Identifying multilayer differential core networks and effective discriminant features for driver fatigue detection

Driver fatigue detection based on EEG has received a lot of attention. In this paper, from the initial brain functional networks of EEG, we first identify multilayer differential core networks based on node and edge discrepancy between different states to capture more discriminant information for the task. Then, the discriminant features are constructed from the resulting multilayer core networks by tensor decomposition and feature selection. The resulting discriminant features contain not only structural information about the network of individual frequency bands, but also additional relational information between the networks of different frequency bands. Our method has the strong ability of information extraction and anti-interference, which can be directly applied to the initial network to identify and utilize weak links with discriminative power. The classification results on the publicly available dataset show that the average accuracy of our method is 9.5% higher than that of the baseline method. When applied to the initial functional network without any pre-processing, the proposed method of this paper can achieve a classification accuracy of 91.14%, which is higher than the results of state-of-the-art related studies on the same dataset. These results indicate that the proposed method is effective and reliable for detecting driver fatigue from EEG.

Fluorescence-enhanced dual signal lateral flow immunoassay for flexible and ultrasensitive detection of monkeypox virus

The outbreak of the monkeypox virus (MPXV) worldwide in 2022 highlights the need for a rapid and low-cost MPXV detection tool for effectively monitoring and controlling monkeypox disease. In this study, we developed a flexible lateral flow immunoassay (LFIA) with strong colorimetric and enhanced fluorescence dual-signal output for the rapid, on-site, and highly sensitive detection of the MPXV antigen in different scenarios. A multilayered SiO2-Au core dual-quantum dot (QD) shell nanocomposite (named SiO2-Au/DQD), which consists of a large SiO2 core (~ 200 nm), one layer of density-controlled gold nanoparticles (AuNPs, 20 nm), and thousands of small QDs, was fabricated instead of a traditional colorimetric nanotag (i.e., AuNPs) and a fluorescent nanotag (QD nanobead) to simultaneously provide good stability, strong colorimetric ability and superior fluorescence intensity. With the dual-signal output LFIA, we achieved the specific screening of the MPXV antigen (A29L) in 15 min, with detection limits of 0.5 and 0.0021 ng/mL for the colorimetric and fluorometric modes, respectively. Moreover, the colorimetric mode of SiO2-Au/DQD-LFIA exhibits the same sensitivity as the traditional AuNP- LFIA, whereas the overall sensitivity of this method on the basis of the fluorescent signal can achieve 238- and 3.3-fold improvements in sensitivity for MPXV compared with the AuNP-based LFIA and ELISA methods, respectively, indicating the powerful performance and good versatility of the dual-signal method in the point-of-care testing of the MPXV.

Underwater impulsive response of sandwich structure with multilayer foam core

Abstract The coupling between fluid-solid interaction and structural response is a crucial factor in understanding the resistance of sandwich structures to underwater blasts. In this study, we present a theoretical model that predicts the dynamic response of multilayer foam core sandwich beams subjected to underwater impulses. We carried out a time-scale intercoupling analysis by considering the compressible core in both incident impulse and structural response. In the incident impulse coupling phase, the one-dimensional fluid-structure interaction in terms of cavitation evolution is conducted to obtain the incident pressure profile. A four inter-stages response model is proposed for further analyze the structural response coupling phase and its coupling with core strength. Explicit finite element calculations are performed to verify the theoretical results in terms of the velocity profile, transverse deflection, and core compression. The results suggest that the interaction between the four stages of the dynamic response is significantly influenced by the impulsive intensity and core strength, and the sandwich beam does not undergo all the four stages. The equivalent core strength used in the theoretical analysis is confirmed accurate to predicts impact resistance of the corresponding graded core sandwich beam, which is inferior to the sandwich beam with uniform cores, despite having the same areal mass.

Experimental Investigation on Layer Subdivision Water Injection in Multilayer Heterogeneous Reservoirs.

Layer subdivision is currently one of the principal techniques employed to solve interlayer contradictions during water injection in multilayer heterogeneous reservoirs, but experimental research on the mechanism and the corresponding implementation plans is lacking. In this study, a multilayer heterogeneous core model was designed, and physical simulation experiments with different subdivisions and variation coefficients were conducted. Furthermore, the influence of the subdivision degree on the water injection development effect was analyzed, and the dynamic characteristics of the oil displacement of each sublayer were compared. Finally, the boundary standard of the layer subdivision was discussed. The results demonstrate that the water breakthrough appears rapidly in the high-permeability layer, and water channeling is easily formed after water flooding. The remaining oil is mostly retained in the low-permeability layer. Layer subdivision water injection can effectively reduce the high water cutoff and improve the oil recovery. The oil recovery increases with the layer subdivision degree, while the incremental rate decreases gradually. The low-permeability layer is observed to be the main layer contributing to the increase in the total recovery of multilayer reservoirs, with a contribution rate that initially increases and subsequently decreases with the increasing subdivision degree, from 0.9 to 11.9, and 29.8%, and subsequently drops to 15.1% during the general water injection with 2-, 4-, and 8-layer subdivision mining. The heterogeneity variation coefficient of 0.55 is used as the subdivision standard to divide different permeability layers to be developed as 1 layer in the multilayer heterogeneous reservoir.

Experimental investigations into the dynamic response of sandwich panels with multi-layered corrugated cores subjected to underwater impulsive load

Sandwich panels with multi-layered core have attractive performance due to the excellent designability and tailorable mechanical properties. In present study, the dynamic responses of the sandwich panels with multi-layered corrugated core were investigated experimentally under underwater impulsive loads. In order to exploit the potential for performance improvement, some attempts have been made by designing core configuration from several aspects including stack orientation, layer number, core gradation and core topology. Experimental results indicate that the core in the cross-stacked would deteriorate back face deflection. The core with three layers performed best in constraint back face deflection because of the well balance between energy absorption and residual flexural stiffness. The core gradation in wall thickness would reduce back face deflection, while the one in corrugation angle would increase back face deflection. The core topology designed into reentrant trapezoidal corrugation behaved effectively in inhabiting back face deformation due to the periodic progressive collapse mechanism of core webs.

Numerical Studies on Flexural Behaviour of Graded Multi-Layer Puf Cored Sandwich Panels

The present numerical investigation was mainly concerned with the evaluation of flexural properties of graded multi-layered polyurethane foam cored (MLCC) sandwich panels using a novel approach through the medium of general purpose program i.e. FEM/ANSYS. Aiming to the goal, three-point bending analysis was performed on sandwich beam models assumed to be made up of composite face sheets (GFRP) and graded multi-layer polyurethane foam cores of different layer densities. Finite element models of sandwich beams were obtained successfully using nonlinear shell 91 elements for face sheets (orthotropic material) and 8-noded shell 98 elements for core (isotropic material).Various multi-layer core configurations in a stack of three layered core were studied with great care. Prior to actual task, the proposed evaluation technique was verified using bench marks. Series of multi-layered cored beam models of different core configurations and span length were analysed in order to study the influence of different graded (density) layer configuration on flexural properties. The present studies reveals that use of MLCC panels for sandwich construction can provide improved flexural properties and hence these panels could be the better choice for structures under non uniform bending and shear loads due to their higher shear stiffness values compared to soft PUF cored panels. Furthermore the MLCC-2 panels in which layers arranged in order of higher to lower density between compression face and tension face stand better among all the possible core configurations.