Macro-scale modelling of the impact response of 3D woven composites for aerospace applications

The objective of this work is to develop a reliable simulation methodology that can be applied to predict the impact response of the components made with 3D textile composites in aero engine applications. Textile composites are excellent candidate materials for the design of aero engine fan containment casings, which are required to sustain the high velocity impact during a fan blade out (FBO) event. This work is focused on a particular form of 3D woven textile composites, in which reinforcement through the thickness is provided by the interlocking weft or warp yarns. An extensive experimental characterisation was conducted for the composites with four different types of reinforcement. The in-plane mechanical properties under the quasi-static tensile, compressive and shear loadings were obtained. The compressive properties at high strain rate were determined in split Hopkinson pressure bar tests. In additional to that, ballistic impact tests were conducted with these composite materials to study their response to high velocity impact loads. The properties determined in the mechanical tests were employed to specify the input data for a commercially available material model in the finite element (FE) software, LS-DYNA. The model was validated by simulating the ballistic impact tests. Good agreement between the predictions and the experimental results was ensured. Once validated, the material model was applied in a range of parametric studies. Since the plate impact tests cannot fully represent the complexity of the FBO event, effects of the projectile shape, the impact obliquity, the target size and the target curvature on the impact performance were investigated by means of parametric studies. To ease the simulation cost encountered during the modelling of a large casing structure, mixed element type analysis (META) was employed for its FE models, where the computationally costly solid elements were coupled with simpler shell elements. The predictive capability of the META models was assessed by comparing their predictions with those of the corresponding solid-element-only models. The study has shown that this method can substantially reduce the simulation time without compromising the accuracy of predictions

Tetra­aqua­bis­[N,N′-bis­(pyridin-3-yl­methyl­idene)benzene-1,4-diamine]­zinc dinitrate 1.49-hydrate

In the title compound, [Zn(C18H14N4)2(H2O)4](NO3)2·1.49H2O, the ZnII atom, lying on an inversion center, is coordinated by two N atoms from two N,N′-bis­(pyridin-3-yl­methyl­idene)benzene-1,4-diamine ligands and four water mol­ecules in a distorted octa­hedral geometry. The nitrate anion is disordered over two sets of sites, with an occupancy ratio of 0.744 (4):0.256 (4). The uncoordinated water mol­ecule is also disordered with an occupancy factor of 0.744 (4). O—H⋯O and O—H⋯N hydrogen bonds link the complex cations, nitrate anions and uncoordinated water mol­ecules into a supra­molecular layer parallel to (102)

Controllable parameters as the essential components in the analysis, manufacturing and design of 3D woven composites

The comprehensive design feasibility for woven composites has been established by identifying the missing component in the design tool for these materials, the so-called controllable parameters. These are the parameters that are involved, directly or indirectly, in manufacturing of woven preforms, and they include the tow densities, the number and the size of filaments in a tow and intra-tow fibre volume fractions. Controllable parameters have been related through a simple procedure to the conventional geometric parameters of woven composites, which eliminates the need for their costly, inefficient, and often unreliable measurements. The controllable parameters provide sufficient representation of woven geometry in terms of both modelling and manufacture, thus offering common terminology to the woven composite designers and manufacturers. This also allows to naturally involve the practical considerations and manufacturing restrictions in material design exercises. With controllable parameters being incorporated in woven composite design framework, a direct analogy can be drawn to classical lamination theory-based design for conventional laminates. The wide applicability of the design tool has been demonstrated via a series of systematic material characterisation exercises carried out with woven composites of sufficiently different internal architectures and constituents, which also showed good predictive capability of the models involved

Genetic liability for diet-derived circulating antioxidants, oxidative stress, and risk of osteoarthritis: a Mendelian randomization study

BackgroundAlthough well-documented, the causal relationships between diet-derived circulating antioxidants, oxidative stress, and osteoarthritis (OA) are equivocal. The objective of this study is to employ two-sample Mendelian randomization (MR) to investigate possible causal relationships among dietary-derived circulating antioxidants, oxidative stress damage indicators, and OA risk.MethodsSingle-nucleotide polymorphisms for diet-derived circulating antioxidants (ascorbate, β-carotene, lycopene, retinol, and α-and γ-tocopherol), assessed as absolute levels and metabolites, as well as oxidative stress injury biomarkers (GSH, GPX, CAT, SOD, albumin, and total bilirubin), were retrieved from the published data and were used as genetic instrumental variables. Summary statistics for gene–OA associations were obtained from publicly available and two relatively large-scale GWAS meta-analyses to date. The inverse-variance weighting method was utilized as the primary MR analysis. Moreover, multivariable MR was used to determine if mediators (BMI and smoking) causally mediated any connection. Furthermore, for each exposure, MR analyses were conducted per outcome database and then meta-analyzed.ResultsGenetically predicted absolute retinol level was causally associated with hip OA risk [odds ratios (ORs) = 0.40, 95% confidence interval (CI) = 0.24–0.68, FDR-corrected p = 0.042]. Moreover, genetically predicted albumin level was causally associated with total OA risk (OR = 0.80, 95% CI = 0.75–0.86, FDR-corrected p = 2.20E-11), as well as the risk of hip OA (OR = 0.75, 95% CI = 0.68–0.84, FDR-corrected p = 1.38E-06) and knee OA (OR = 0.82, 95% CI = 0.76–0.89, FDR-corrected p = 4.49E-06). In addition, MVMR confirmed that the effect of albumin on hip OA is independent of smoking initiation, alcoholic drinks per week, and moderate-to-vigorous physical activity levels but may be influenced by BMI.ConclusionEvidence from our study supports a potentially protective effect of high levels of retinol and albumin on OA risk

Dynamic changes of rumen bacteria and their fermentative ability in high-producing dairy cows during the late perinatal period

BackgroundHigh-producing dairy cows face varying degrees of metabolic stress and challenges during the late perinatal period, resulting in ruminal bacteria abundance and their fermentative ability occurring as a series of changes. However, the dynamic changes are still not clear.Aims/methodsTen healthy, high-producing Holstein dairy cows with similar body conditions and the same parity were selected, and ruminal fluid from the dairy cows at postpartum 0, 7, 14, and 21 d was collected before morning feeding. 16S rRNA high-throughput sequencing, GC-MS/MS targeted metabolomics, and UPLC-MS/MS untargeted metabolomics were applied in the study to investigate the dynamic changes within 21 d postpartum.ResultsThe results displayed that the structures of ruminal bacteria were significantly altered from 0 to 7 d postpartum (R = 0.486, P = 0.002), reflecting the significantly declining abundances of Euryarchaeota and Chloroflexi phyla and Christensenellaceae, Methanobrevibacter, and Flexilinea genera (P < 0.05) and the obviously ascending abundances of Ruminococcaceae, Moryella, Pseudobutyrivibrio, and Prevotellaceae genera at 7 d postpartum (P < 0.05). The structures of ruminal bacteria also varied significantly from 7 to 14 d postpartum (R = 0.125, P = 0.022), reflecting the reducing abundances of Christensenellaceae, Ruminococcaceae, and Moryella genera (P < 0.05), and the elevating abundances of Sharpea and Olsenella genera at 14 d postpartum (P < 0.05). The metabolic profiles of ruminal SCFAs were obviously varied from 0 to 7 d postpartum, resulting in higher levels of propionic acid, butyric acid, and valeric acid at 7 d postpartum (P < 0.05); the metabolic profiles of other ruminal metabolites were significantly shifted from 0 to 7 d postpartum, with 27 significantly elevated metabolites and 35 apparently reduced metabolites (P < 0.05). The correlation analysis indicated that propionic acid was positively correlated with Prevotellaceae and Ruminococcaceae (P < 0.05), negatively correlated with Methanobrevibacter (P < 0.01); butyric acid was positively associated with Prevotellaceae, Ruminococcaceae, and Pseudobutyrivibrio (P < 0.05), negatively associated with Christensenellaceae (P < 0.01); valeric acid was positively linked with Prevotellaceae and Ruminococcaceae (P < 0.05); pyridoxal was positively correlated with Flexilinea and Methanobrevibacter (P < 0.05) and negatively correlated with Ruminococcaceae (P < 0.01); tyramine was negatively linked with Ruminococcaceae (P < 0.01).ConclusionThe findings contribute to the decision of nutritional management and prevention of metabolic diseases in high-producing dairy cows during the late perinatal period

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Macro-scale modelling of the impact response of 3D woven composites for aerospace applications

The objective of this work is to develop a reliable simulation methodology that can be applied to predict the impact response of the components made with 3D textile composites in aero engine applications. Textile composites are excellent candidate materials for the design of aero engine fan containment casings, which are required to sustain the high velocity impact during a fan blade out (FBO) event. This work is focused on a particular form of 3D woven textile composites, in which reinforcement through the thickness is provided by the interlocking weft or warp yarns. An extensive experimental characterisation was conducted for the composites with four different types of reinforcement. The in-plane mechanical properties under the quasi-static tensile, compressive and shear loadings were obtained. The compressive properties at high strain rate were determined in split Hopkinson pressure bar tests. In additional to that, ballistic impact tests were conducted with these composite materials to study their response to high velocity impact loads. The properties determined in the mechanical tests were employed to specify the input data for a commercially available material model in the finite element (FE) software, LS-DYNA. The model was validated by simulating the ballistic impact tests. Good agreement between the predictions and the experimental results was ensured. Once validated, the material model was applied in a range of parametric studies. Since the plate impact tests cannot fully represent the complexity of the FBO event, effects of the projectile shape, the impact obliquity, the target size and the target curvature on the impact performance were investigated by means of parametric studies. To ease the simulation cost encountered during the modelling of a large casing structure, mixed element type analysis (META) was employed for its FE models, where the computationally costly solid elements were coupled with simpler shell elements. The predictive capability of the META models was assessed by comparing their predictions with those of the corresponding solid-element-only models. The study has shown that this method can substantially reduce the simulation time without compromising the accuracy of predictions

Electrochemical synthesis and characterization of graphene oxide based composite film

Graphene oxide is a new type of carbon material with excellent performance, having high specific surface area and abundant functional groups on the surface. Its large number of oxygen-containing functional groups makes the carbon layers negatively charged, and positively charged cations can easily enter between the layers and prop up the layer spacing, providing favorable conditions for loading of polymers and inorganic nanoparticles. The graphene oxide composites obtained by modifying the surface of graphene oxide include polymer-based composites as well as inorganic composites, all of which show superior properties and have a wide range of applications. Composite of conductive polymers and graphene oxide has become a hot research topic because the conductive synergy between graphene oxide and conductive polymers can enhance the conductivity of the matrix and at the same time achieve structural enhancement. 1,3,5-Tris(4-cyanopyridinium-1-ylmethyl)-2,4,6-trimethylbenzenetribromide ( T0 ) in tight molecular contact with reduced graphene oxide ( rGO ) , that is, T0 / rGO, were electropolymerized and characterized. The composite shows better electrical conductivity and electron store ability. The polymerization process includes (i) molecular self-assembling of T0s on individual GO sheets yielding colloidal T0/rGO and (ii) efficient GO/rGO transformation by electrochemical method. Further studies on the properties of the composites are analyzed by Cyclic Voltammetry(CV) , Differential Pulse Voltammetry ( DPV) ,Electrochemical Impedance Spectroscopy ( EIS ) , Ultraviolet and visible spectrophotometry (UV ), Scanning electron microscope ( SEM ) images etc

Theoretical investigation on the electronic and thermoelectric properties of RuSb2Te compound

The skutterudites are an excellent candidate for thermoelectric materials used in mechanic free heat pump and electric generator. Using the ab initio density functional theory we have calculated the electronic band structure and thermoelectric properties of skutterudite RuSb2Te. RuSb2Te compound belongs to an indirect band gap semiconductor. The density of states has a sharp upturn at the conduction band edge and is very low at the valence band top. This feature suggests that Seebeck coefficient is larger for n doped than for p doped RuSb2Te compound. The calculated Seebeck coefficient confirms this trend. It is in a qualitative agreement with the experiments if the temperature is not too high